Merge pull request #637 from zackdever/metrics

Metrics java port
2016-04-14 11:02:01 -07:00
parent 0c94b83a2d e2b340c440
commit cf679ae387
32 changed files with 1985 additions and 112 deletions
--- a/kafka/consumer/fetcher.py
+++ b/kafka/consumer/fetcher.py
@@ -3,11 +3,13 @@ from __future__ import absolute_import
 import collections
 import copy
 import logging
+import time

 import six

 import kafka.errors as Errors
 from kafka.future import Future
+from kafka.metrics.stats import Avg, Count, Max, Rate
 from kafka.protocol.fetch import FetchRequest
 from kafka.protocol.message import PartialMessage
 from kafka.protocol.offset import OffsetRequest, OffsetResetStrategy
@@ -40,7 +42,8 @@ class Fetcher(six.Iterator):
        'api_version': (0, 8, 0),
    }

-    def __init__(self, client, subscriptions, **configs):
+    def __init__(self, client, subscriptions, metrics, metric_group_prefix,
+                 **configs):
        """Initialize a Kafka Message Fetcher.

        Keyword Arguments:
@@ -68,8 +71,6 @@ class Fetcher(six.Iterator):
                the messages occurred. This check adds some overhead, so it may
                be disabled in cases seeking extreme performance. Default: True
        """
-                 #metrics=None,
-                 #metric_group_prefix='consumer',
        self.config = copy.copy(self.DEFAULT_CONFIG)
        for key in self.config:
            if key in configs:
@@ -83,8 +84,7 @@ class Fetcher(six.Iterator):
        self._record_too_large_partitions = dict() # {topic_partition: offset}
        self._iterator = None
        self._fetch_futures = collections.deque()
-
-        #self.sensors = FetchManagerMetrics(metrics, metric_group_prefix)
+        self._sensors = FetchManagerMetrics(metrics, metric_group_prefix)

    def init_fetches(self):
        """Send FetchRequests asynchronously for all assigned partitions.
@@ -109,7 +109,7 @@ class Fetcher(six.Iterator):
            if self._client.ready(node_id):
                log.debug("Sending FetchRequest to node %s", node_id)
                future = self._client.send(node_id, request)
-                future.add_callback(self._handle_fetch_response, request)
+                future.add_callback(self._handle_fetch_response, request, time.time())
                future.add_errback(log.error, 'Fetch to node %s failed: %s', node_id)
                futures.append(future)
        self._fetch_futures.extend(futures)
@@ -575,10 +575,11 @@ class Fetcher(six.Iterator):
                partition_data.items())
        return requests

-    def _handle_fetch_response(self, request, response):
+    def _handle_fetch_response(self, request, send_time, response):
        """The callback for fetch completion"""
-        #total_bytes = 0
-        #total_count = 0
+        total_bytes = 0
+        total_count = 0
+        recv_time = time.time()

        fetch_offsets = {}
        for topic, partitions in request.topics:
@@ -609,6 +610,7 @@ class Fetcher(six.Iterator):
                                  position)
                        continue

+                    num_bytes = 0
                    partial = None
                    if messages and isinstance(messages[-1][-1], PartialMessage):
                        partial = messages.pop()
@@ -618,18 +620,18 @@ class Fetcher(six.Iterator):
                                  " offset %d to buffered record list", tp,
                                  position)
                        self._records.append((fetch_offset, tp, messages))
-                        #last_offset, _, _ = messages[-1]
-                        #self.sensors.records_fetch_lag.record(highwater - last_offset)
+                        last_offset, _, _ = messages[-1]
+                        self._sensors.records_fetch_lag.record(highwater - last_offset)
+                        num_bytes = sum(msg[1] for msg in messages)
                    elif partial:
                        # we did not read a single message from a non-empty
                        # buffer because that message's size is larger than
                        # fetch size, in this case record this exception
                        self._record_too_large_partitions[tp] = fetch_offset

-                    # TODO: bytes metrics
-                    #self.sensors.record_topic_fetch_metrics(tp.topic, num_bytes, parsed.size());
-                    #totalBytes += num_bytes;
-                    #totalCount += parsed.size();
+                    self._sensors.record_topic_fetch_metrics(topic, num_bytes, len(messages))
+                    total_bytes += num_bytes
+                    total_count += len(messages)
                elif error_type in (Errors.NotLeaderForPartitionError,
                                    Errors.UnknownTopicOrPartitionError):
                    self._client.cluster.request_update()
@@ -649,56 +651,82 @@ class Fetcher(six.Iterator):
                else:
                    raise error_type('Unexpected error while fetching data')

-        """TOOD - metrics
-        self.sensors.bytesFetched.record(totalBytes)
-        self.sensors.recordsFetched.record(totalCount)
-        self.sensors.fetchThrottleTimeSensor.record(response.getThrottleTime())
-        self.sensors.fetchLatency.record(resp.requestLatencyMs())
+        self._sensors.bytes_fetched.record(total_bytes)
+        self._sensors.records_fetched.record(total_count)
+        self._sensors.fetch_throttle_time_sensor.record(response['throttle_time_ms'])
+        self._sensors.fetch_latency.record((recv_time - send_time) * 1000)


 class FetchManagerMetrics(object):
    def __init__(self, metrics, prefix):
        self.metrics = metrics
-        self.group_name = prefix + "-fetch-manager-metrics"
+        self.group_name = '%s-fetch-manager-metrics' % prefix

-        self.bytes_fetched = metrics.sensor("bytes-fetched")
-        self.bytes_fetched.add(metrics.metricName("fetch-size-avg", self.group_name,
-            "The average number of bytes fetched per request"), metrics.Avg())
-        self.bytes_fetched.add(metrics.metricName("fetch-size-max", self.group_name,
-            "The maximum number of bytes fetched per request"), metrics.Max())
-        self.bytes_fetched.add(metrics.metricName("bytes-consumed-rate", self.group_name,
-            "The average number of bytes consumed per second"), metrics.Rate())
+        self.bytes_fetched = metrics.sensor('bytes-fetched')
+        self.bytes_fetched.add(metrics.metric_name('fetch-size-avg', self.group_name,
+            'The average number of bytes fetched per request'), Avg())
+        self.bytes_fetched.add(metrics.metric_name('fetch-size-max', self.group_name,
+            'The maximum number of bytes fetched per request'), Max())
+        self.bytes_fetched.add(metrics.metric_name('bytes-consumed-rate', self.group_name,
+            'The average number of bytes consumed per second'), Rate())

-        self.records_fetched = self.metrics.sensor("records-fetched")
-        self.records_fetched.add(metrics.metricName("records-per-request-avg", self.group_name,
-            "The average number of records in each request"), metrics.Avg())
-        self.records_fetched.add(metrics.metricName("records-consumed-rate", self.group_name,
-            "The average number of records consumed per second"), metrics.Rate())
+        self.records_fetched = self.metrics.sensor('records-fetched')
+        self.records_fetched.add(metrics.metric_name('records-per-request-avg', self.group_name,
+            'The average number of records in each request'), Avg())
+        self.records_fetched.add(metrics.metric_name('records-consumed-rate', self.group_name,
+            'The average number of records consumed per second'), Rate())

-        self.fetch_latency = metrics.sensor("fetch-latency")
-        self.fetch_latency.add(metrics.metricName("fetch-latency-avg", self.group_name,
-            "The average time taken for a fetch request."), metrics.Avg())
-        self.fetch_latency.add(metrics.metricName("fetch-latency-max", self.group_name,
-            "The max time taken for any fetch request."), metrics.Max())
-        self.fetch_latency.add(metrics.metricName("fetch-rate", self.group_name,
-            "The number of fetch requests per second."), metrics.Rate(metrics.Count()))
+        self.fetch_latency = metrics.sensor('fetch-latency')
+        self.fetch_latency.add(metrics.metric_name('fetch-latency-avg', self.group_name,
+            'The average time taken for a fetch request.'), Avg())
+        self.fetch_latency.add(metrics.metric_name('fetch-latency-max', self.group_name,
+            'The max time taken for any fetch request.'), Max())
+        self.fetch_latency.add(metrics.metric_name('fetch-rate', self.group_name,
+            'The number of fetch requests per second.'), Rate(sampled_stat=Count()))

-        self.records_fetch_lag = metrics.sensor("records-lag")
-        self.records_fetch_lag.add(metrics.metricName("records-lag-max", self.group_name,
-            "The maximum lag in terms of number of records for any partition in self window"), metrics.Max())
+        self.records_fetch_lag = metrics.sensor('records-lag')
+        self.records_fetch_lag.add(metrics.metric_name('records-lag-max', self.group_name,
+            'The maximum lag in terms of number of records for any partition in self window'), Max())

-        self.fetch_throttle_time_sensor = metrics.sensor("fetch-throttle-time")
-        self.fetch_throttle_time_sensor.add(metrics.metricName("fetch-throttle-time-avg", self.group_name,
-            "The average throttle time in ms"), metrics.Avg())
-        self.fetch_throttle_time_sensor.add(metrics.metricName("fetch-throttle-time-max", self.group_name,
-            "The maximum throttle time in ms"), metrics.Max())
+        self.fetch_throttle_time_sensor = metrics.sensor('fetch-throttle-time')
+        self.fetch_throttle_time_sensor.add(metrics.metric_name('fetch-throttle-time-avg', self.group_name,
+            'The average throttle time in ms'), Avg())
+        self.fetch_throttle_time_sensor.add(metrics.metric_name('fetch-throttle-time-max', self.group_name,
+            'The maximum throttle time in ms'), Max())

-        def record_topic_fetch_metrics(topic, num_bytes, num_records):
-            # record bytes fetched
-            name = '.'.join(["topic", topic, "bytes-fetched"])
-            self.metrics[name].record(num_bytes);
+    def record_topic_fetch_metrics(self, topic, num_bytes, num_records):
+        metric_tags = {'topic': topic.replace('.', '_')}

-            # record records fetched
-            name = '.'.join(["topic", topic, "records-fetched"])
-            self.metrics[name].record(num_records)
-        """
+        # record bytes fetched
+        name = '.'.join(['topic', topic, 'bytes-fetched'])
+        bytes_fetched = self.metrics.get_sensor(name)
+        if not bytes_fetched:
+            bytes_fetched = self.metrics.sensor(name)
+            bytes_fetched.add(self.metrics.metric_name('fetch-size-avg',
+                    self.group_name,
+                    'The average number of bytes fetched per request for topic %s' % topic,
+                    metric_tags), Avg())
+            bytes_fetched.add(self.metrics.metric_name('fetch-size-max',
+                    self.group_name,
+                    'The maximum number of bytes fetched per request for topic %s' % topic,
+                    metric_tags), Max())
+            bytes_fetched.add(self.metrics.metric_name('bytes-consumed-rate',
+                    self.group_name,
+                    'The average number of bytes consumed per second for topic %s' % topic,
+                    metric_tags), Rate())
+        bytes_fetched.record(num_bytes)
+
+        # record records fetched
+        name = '.'.join(['topic', topic, 'records-fetched'])
+        records_fetched = self.metrics.get_sensor(name)
+        if not records_fetched:
+            records_fetched = self.metrics.sensor(name)
+            records_fetched.add(self.metrics.metric_name('records-per-request-avg',
+                    self.group_name,
+                    'The average number of records in each request for topic %s' % topic,
+                    metric_tags), Avg())
+            records_fetched.add(self.metrics.metric_name('records-consumed-rate',
+                    self.group_name,
+                    'The average number of records consumed per second for topic %s' % topic,
+                    metric_tags), Rate())
+        records_fetched.record(num_records)
--- a/kafka/consumer/group.py
+++ b/kafka/consumer/group.py
@@ -12,6 +12,7 @@ from kafka.consumer.subscription_state import SubscriptionState
 from kafka.coordinator.consumer import ConsumerCoordinator
 from kafka.coordinator.assignors.range import RangePartitionAssignor
 from kafka.coordinator.assignors.roundrobin import RoundRobinPartitionAssignor
+from kafka.metrics import DictReporter, MetricConfig, Metrics
 from kafka.protocol.offset import OffsetResetStrategy
 from kafka.structs import TopicPartition
 from kafka.version import __version__
@@ -143,6 +144,13 @@ class KafkaConsumer(six.Iterator):
            offset commits; 0.8.0 is what is left. If set to 'auto', will
            attempt to infer the broker version by probing various APIs.
            Default: auto
+        metric_reporters (list): A list of classes to use as metrics reporters.
+            Implementing the AbstractMetricsReporter interface allows plugging
+            in classes that will be notified of new metric creation. Default: []
+        metrics_num_samples (int): The number of samples maintained to compute
+            metrics. Default: 2
+        metrics_sample_window_ms (int): The number of samples maintained to
+            compute metrics. Default: 30000

    Note:
        Configuration parameters are described in more detail at
@@ -181,9 +189,9 @@ class KafkaConsumer(six.Iterator):
        'ssl_keyfile': None,
        'api_version': 'auto',
        'connections_max_idle_ms': 9 * 60 * 1000, # not implemented yet
-        #'metric_reporters': None,
-        #'metrics_num_samples': 2,
-        #'metrics_sample_window_ms': 30000,
+        'metric_reporters': [],
+        'metrics_num_samples': 2,
+        'metrics_sample_window_ms': 30000,
    }

    def __init__(self, *topics, **configs):
@@ -202,6 +210,16 @@ class KafkaConsumer(six.Iterator):
                        new_config, self.config['auto_offset_reset'])
            self.config['auto_offset_reset'] = new_config

+        metrics_tags = {'client-id': self.config['client_id']}
+        metric_config = MetricConfig(samples=self.config['metrics_num_samples'],
+                                     time_window_ms=self.config['metrics_sample_window_ms'],
+                                     tags=metrics_tags)
+        reporters = [reporter() for reporter in self.config['metric_reporters']]
+        reporters.append(DictReporter('kafka.consumer'))
+        self._metrics = Metrics(metric_config, reporters)
+        metric_group_prefix = 'consumer'
+        # TODO _metrics likely needs to be passed to KafkaClient, etc.
+
        self._client = KafkaClient(**self.config)

        # Check Broker Version if not set explicitly
@@ -215,16 +233,15 @@ class KafkaConsumer(six.Iterator):

        self._subscription = SubscriptionState(self.config['auto_offset_reset'])
        self._fetcher = Fetcher(
-            self._client, self._subscription, **self.config)
+            self._client, self._subscription, self._metrics, metric_group_prefix, **self.config)
        self._coordinator = ConsumerCoordinator(
-            self._client, self._subscription,
+            self._client, self._subscription, self._metrics, metric_group_prefix,
            assignors=self.config['partition_assignment_strategy'],
            **self.config)
        self._closed = False
        self._iterator = None
        self._consumer_timeout = float('inf')

-        #self.metrics = None
        if topics:
            self._subscription.subscribe(topics=topics)
            self._client.set_topics(topics)
@@ -277,7 +294,7 @@ class KafkaConsumer(six.Iterator):
        log.debug("Closing the KafkaConsumer.")
        self._closed = True
        self._coordinator.close()
-        #self.metrics.close()
+        self._metrics.close()
        self._client.close()
        try:
            self.config['key_deserializer'].close()
--- a/kafka/coordinator/base.py
+++ b/kafka/coordinator/base.py
@@ -658,7 +658,7 @@ class GroupCoordinatorMetrics(object):
        self.heartbeat_latency.add(metrics.metricName(
            "heartbeat-rate", self.group_name,
            "The average number of heartbeats per second",
-            tags), metrics.Rate(metrics.Count()))
+            tags), metrics.Rate(sampled_stat=metrics.Count()))

        self.join_latency = metrics.sensor("join-latency")
        self.join_latency.add(metrics.metricName(
@@ -672,7 +672,7 @@ class GroupCoordinatorMetrics(object):
        self.join_latency.add(metrics.metricName(
            "join-rate", self.group_name,
            "The number of group joins per second",
-            tags), metrics.Rate(metrics.Count()))
+            tags), metrics.Rate(sampled_stat=metrics.Count()))

        self.sync_latency = metrics.sensor("sync-latency")
        self.sync_latency.add(metrics.metricName(
@@ -686,7 +686,7 @@ class GroupCoordinatorMetrics(object):
        self.sync_latency.add(metrics.metricName(
            "sync-rate", self.group_name,
            "The number of group syncs per second",
-            tags), metrics.Rate(metrics.Count()))
+            tags), metrics.Rate(sampled_stat=metrics.Count()))

        """
        lastHeartbeat = Measurable(
--- a/kafka/coordinator/consumer.py
+++ b/kafka/coordinator/consumer.py
@@ -14,6 +14,8 @@ from .assignors.roundrobin import RoundRobinPartitionAssignor
 from .protocol import ConsumerProtocol
 from .. import errors as Errors
 from ..future import Future
+from ..metrics import AnonMeasurable
+from ..metrics.stats import Avg, Count, Max, Rate
 from ..protocol.commit import OffsetCommitRequest, OffsetFetchRequest
 from ..structs import OffsetAndMetadata, TopicPartition
 from ..util import WeakMethod
@@ -36,7 +38,8 @@ class ConsumerCoordinator(BaseCoordinator):
        'api_version': (0, 9),
    }

-    def __init__(self, client, subscription, **configs):
+    def __init__(self, client, subscription, metrics, metric_group_prefix,
+                 **configs):
        """Initialize the coordination manager.

        Keyword Arguments:
@@ -97,10 +100,8 @@ class ConsumerCoordinator(BaseCoordinator):
                interval = self.config['auto_commit_interval_ms'] / 1000.0
                self._auto_commit_task = AutoCommitTask(weakref.proxy(self), interval)

-        # metrics=None,
-        # metric_group_prefix=None,
-        # metric_tags=None,
-        # self.sensors = ConsumerCoordinatorMetrics(metrics, metric_group_prefix, metric_tags)
+        self._sensors = ConsumerCoordinatorMetrics(metrics, metric_group_prefix,
+                                                   self._subscription)

    def __del__(self):
        if hasattr(self, '_auto_commit_task') and self._auto_commit_task:
@@ -470,12 +471,13 @@ class ConsumerCoordinator(BaseCoordinator):

        future = Future()
        _f = self._client.send(node_id, request)
-        _f.add_callback(self._handle_offset_commit_response, offsets, future)
+        _f.add_callback(self._handle_offset_commit_response, offsets, future, time.time())
        _f.add_errback(self._failed_request, node_id, request, future)
        return future

-    def _handle_offset_commit_response(self, offsets, future, response):
-        #self.sensors.commit_latency.record(response.requestLatencyMs())
+    def _handle_offset_commit_response(self, offsets, future, send_time, response):
+        # TODO look at adding request_latency_ms to response (like java kafka)
+        self._sensors.commit_latency.record((time.time() - send_time) * 1000)
        unauthorized_topics = set()

        for topic, partitions in response.topics:
@@ -720,38 +722,25 @@ class AutoCommitTask(object):
        self._reschedule(next_at)


-# TODO
-"""
 class ConsumerCoordinatorMetrics(object):
-    def __init__(self, metrics, prefix, tags):
+    def __init__(self, metrics, metric_group_prefix, subscription):
        self.metrics = metrics
-        self.group_name = prefix + "-coordinator-metrics"
+        self.metric_group_name = '%s-coordinator-metrics' % metric_group_prefix

-        self.commit_latency = metrics.sensor("commit-latency")
-        self.commit_latency.add(metrics.MetricName(
-            "commit-latency-avg", self.group_name,
-            "The average time taken for a commit request",
-            tags), metrics.Avg())
-        self.commit_latency.add(metrics.MetricName(
-            "commit-latency-max", self.group_name,
-            "The max time taken for a commit request",
-            tags), metrics.Max())
-        self.commit_latency.add(metrics.MetricName(
-            "commit-rate", self.group_name,
-            "The number of commit calls per second",
-            tags), metrics.Rate(metrics.Count()))
+        self.commit_latency = metrics.sensor('commit-latency')
+        self.commit_latency.add(metrics.metric_name(
+            'commit-latency-avg', self.metric_group_name,
+            'The average time taken for a commit request'), Avg())
+        self.commit_latency.add(metrics.metric_name(
+            'commit-latency-max', self.metric_group_name,
+            'The max time taken for a commit request'), Max())
+        self.commit_latency.add(metrics.metric_name(
+            'commit-rate', self.metric_group_name,
+            'The number of commit calls per second'), Rate(sampled_stat=Count()))

-        '''
-        def _num_partitions(config, now):
-            new Measurable() {
-                public double measure(MetricConfig config, long now) {
-                    return subscriptions.assignedPartitions().size();
-                }
-            };
-        metrics.addMetric(new MetricName("assigned-partitions",
-            this.metricGrpName,
-            "The number of partitions currently assigned to this consumer",
-            tags),
-            numParts);
-        '''
-"""
+        num_parts = AnonMeasurable(lambda config, now:
+                                   len(subscription.assigned_partitions()))
+        metrics.add_metric(metrics.metric_name(
+            'assigned-partitions', self.metric_group_name,
+            'The number of partitions currently assigned to this consumer'),
+            num_parts)
--- a/kafka/errors.py
+++ b/kafka/errors.py
@@ -361,6 +361,10 @@ class KafkaConfigurationError(KafkaError):
    pass


+class QuotaViolationError(KafkaError):
+    pass
+
+
 class AsyncProducerQueueFull(KafkaError):
    def __init__(self, failed_msgs, *args):
        super(AsyncProducerQueueFull, self).__init__(*args)
--- a/kafka/metrics/init.py
+++ b/kafka/metrics/init.py
@@ -0,0 +1,13 @@
+from .compound_stat import NamedMeasurable
+from .dict_reporter import DictReporter
+from .kafka_metric import KafkaMetric
+from .measurable import AnonMeasurable
+from .metric_config import MetricConfig
+from .metric_name import MetricName
+from .metrics import Metrics
+from .quota import Quota
+
+__all__ = [
+    'AnonMeasurable', 'DictReporter', 'KafkaMetric', 'MetricConfig',
+    'MetricName', 'Metrics', 'NamedMeasurable', 'Quota'
+]
--- a/kafka/metrics/compound_stat.py
+++ b/kafka/metrics/compound_stat.py
@@ -0,0 +1,32 @@
+import abc
+
+from kafka.metrics.stat import AbstractStat
+
+
+class AbstractCompoundStat(AbstractStat):
+    """
+    A compound stat is a stat where a single measurement and associated
+    data structure feeds many metrics. This is the example for a
+    histogram which has many associated percentiles.
+    """
+    __metaclass__ = abc.ABCMeta
+
+    def stats(self):
+        """
+        Return list of NamedMeasurable
+        """
+        raise NotImplementedError
+
+
+class NamedMeasurable(object):
+    def __init__(self, metric_name, measurable_stat):
+        self._name = metric_name
+        self._stat = measurable_stat
+
+    @property
+    def name(self):
+        return self._name
+
+    @property
+    def stat(self):
+        return self._stat
--- a/kafka/metrics/dict_reporter.py
+++ b/kafka/metrics/dict_reporter.py
@@ -0,0 +1,81 @@
+import logging
+import threading
+
+from kafka.metrics.metrics_reporter import AbstractMetricsReporter
+
+logger = logging.getLogger(__name__)
+
+
+class DictReporter(AbstractMetricsReporter):
+    """A basic dictionary based metrics reporter.
+
+    Store all metrics in a two level dictionary of category > name > metric.
+    """
+    def __init__(self, prefix=''):
+        self._lock = threading.Lock()
+        self._prefix = prefix if prefix else ''  # never allow None
+        self._store = {}
+
+    def snapshot(self):
+        """
+        Return a nested dictionary snapshot of all metrics and their
+        values at this time. Example:
+        {
+            'category': {
+                'metric1_name': 42.0,
+                'metric2_name': 'foo'
+            }
+        }
+        """
+        return dict((category, dict((name, metric.value())
+                                    for name, metric in list(metrics.items())))
+                    for category, metrics in
+                    list(self._store.items()))
+
+    def init(self, metrics):
+        for metric in metrics:
+            self.metric_change(metric)
+
+    def metric_change(self, metric):
+        with self._lock:
+            category = self.get_category(metric)
+            if category not in self._store:
+                self._store[category] = {}
+            self._store[category][metric.metric_name.name] = metric
+
+    def metric_removal(self, metric):
+        with self._lock:
+            category = self.get_category(metric)
+            metrics = self._store.get(category, {})
+            removed = metrics.pop(metric.metric_name.name, None)
+            if not metrics:
+                self._store.pop(category, None)
+            return removed
+
+    def get_category(self, metric):
+        """
+        Return a string category for the metric.
+
+        The category is made up of this reporter's prefix and the
+        metric's group and tags.
+
+        Examples:
+            prefix = 'foo', group = 'bar', tags = {'a': 1, 'b': 2}
+            returns: 'foo.bar.a=1,b=2'
+
+            prefix = 'foo', group = 'bar', tags = None
+            returns: 'foo.bar'
+
+            prefix = None, group = 'bar', tags = None
+            returns: 'bar'
+        """
+        tags = ','.join('%s=%s' % (k, v) for k, v in
+                        sorted(metric.metric_name.tags.items()))
+        return '.'.join(x for x in
+                        [self._prefix, metric.metric_name.group, tags] if x)
+
+    def configure(self, configs):
+        pass
+
+    def close(self):
+        pass
--- a/kafka/metrics/kafka_metric.py
+++ b/kafka/metrics/kafka_metric.py
@@ -0,0 +1,34 @@
+import time
+
+
+class KafkaMetric(object):
+    # NOTE java constructor takes a lock instance
+    def __init__(self, metric_name, measurable, config):
+        if not metric_name:
+            raise ValueError('metric_name must be non-empty')
+        if not measurable:
+            raise ValueError('measurable must be non-empty')
+        self._metric_name = metric_name
+        self._measurable = measurable
+        self._config = config
+
+    @property
+    def metric_name(self):
+        return self._metric_name
+
+    @property
+    def measurable(self):
+        return self._measurable
+
+    @property
+    def config(self):
+        return self._config
+
+    @config.setter
+    def config(self, config):
+        self._config = config
+
+    def value(self, time_ms=None):
+        if time_ms is None:
+            time_ms = time.time() * 1000
+        return self.measurable.measure(self.config, time_ms)
--- a/kafka/metrics/measurable.py
+++ b/kafka/metrics/measurable.py
@@ -0,0 +1,27 @@
+import abc
+
+
+class AbstractMeasurable(object):
+    """A measurable quantity that can be registered as a metric"""
+    @abc.abstractmethod
+    def measure(self, config, now):
+        """
+        Measure this quantity and return the result
+
+        Arguments:
+            config (MetricConfig): The configuration for this metric
+            now (int): The POSIX time in milliseconds the measurement
+                is being taken
+
+        Returns:
+            The measured value
+        """
+        raise NotImplementedError
+
+
+class AnonMeasurable(AbstractMeasurable):
+    def __init__(self, measure_fn):
+        self._measure_fn = measure_fn
+
+    def measure(self, config, now):
+        return float(self._measure_fn(config, now))
--- a/kafka/metrics/measurable_stat.py
+++ b/kafka/metrics/measurable_stat.py
@@ -0,0 +1,14 @@
+import abc
+
+from kafka.metrics.measurable import AbstractMeasurable
+from kafka.metrics.stat import AbstractStat
+
+
+class AbstractMeasurableStat(AbstractStat, AbstractMeasurable):
+    """
+    An AbstractMeasurableStat is an AbstractStat that is also
+    an AbstractMeasurable (i.e. can produce a single floating point value).
+    This is the interface used for most of the simple statistics such
+    as Avg, Max, Count, etc.
+    """
+    __metaclass__ = abc.ABCMeta
--- a/kafka/metrics/metric_config.py
+++ b/kafka/metrics/metric_config.py
@@ -0,0 +1,31 @@
+import sys
+
+
+class MetricConfig(object):
+    """Configuration values for metrics"""
+    def __init__(self, quota=None, samples=2, event_window=sys.maxsize,
+                 time_window_ms=30 * 1000, tags=None):
+        """
+        Arguments:
+            quota (Quota, optional): Upper or lower bound of a value.
+            samples (int, optional): Max number of samples kept per metric.
+            event_window (int, optional): Max number of values per sample.
+            time_window_ms (int, optional): Max age of an individual sample.
+            tags (dict of {str: str}, optional): Tags for each metric.
+        """
+        self.quota = quota
+        self._samples = samples
+        self.event_window = event_window
+        self.time_window_ms = time_window_ms
+        # tags should be OrderedDict (not supported in py26)
+        self.tags = tags if tags else {}
+
+    @property
+    def samples(self):
+        return self._samples
+
+    @samples.setter
+    def samples(self, value):
+        if value < 1:
+            raise ValueError('The number of samples must be at least 1.')
+        self._samples = value
--- a/kafka/metrics/metric_name.py
+++ b/kafka/metrics/metric_name.py
@@ -0,0 +1,104 @@
+import copy
+
+
+class MetricName(object):
+    """
+    This class encapsulates a metric's name, logical group and its
+    related attributes (tags).
+
+    group, tags parameters can be used to create unique metric names.
+    e.g. domainName:type=group,key1=val1,key2=val2
+
+    Usage looks something like this:
+
+        # set up metrics:
+        metric_tags = {'client-id': 'producer-1', 'topic': 'topic'}
+        metric_config = MetricConfig(tags=metric_tags)
+
+        # metrics is the global repository of metrics and sensors
+        metrics = Metrics(metric_config)
+
+        sensor = metrics.sensor('message-sizes')
+        metric_name = metrics.metric_name('message-size-avg',
+                                          'producer-metrics',
+                                          'average message size')
+        sensor.add(metric_name, Avg())
+
+        metric_name = metrics.metric_name('message-size-max',
+        sensor.add(metric_name, Max())
+
+        tags = {'client-id': 'my-client', 'topic': 'my-topic'}
+        metric_name = metrics.metric_name('message-size-min',
+                                          'producer-metrics',
+                                          'message minimum size', tags)
+        sensor.add(metric_name, Min())
+
+        # as messages are sent we record the sizes
+        sensor.record(message_size)
+    """
+
+    def __init__(self, name, group, description=None, tags=None):
+        """
+        Arguments:
+            name (str): The name of the metric.
+            group (str): The logical group name of the metrics to which this
+                metric belongs.
+            description (str, optional): A human-readable description to
+                include in the metric.
+            tags (dict, optional): Additional key/val attributes of the metric.
+        """
+        if not (name and group):
+            raise Exception('name and group must be non-empty.')
+        if tags is not None and not isinstance(tags, dict):
+            raise Exception('tags must be a dict if present.')
+
+        self._name = name
+        self._group = group
+        self._description = description
+        self._tags = copy.copy(tags)
+        self._hash = 0
+
+    @property
+    def name(self):
+        return self._name
+
+    @property
+    def group(self):
+        return self._group
+
+    @property
+    def description(self):
+        return self._description
+
+    @property
+    def tags(self):
+        return copy.copy(self._tags)
+
+    def __hash__(self):
+        if self._hash != 0:
+            return self._hash
+        prime = 31
+        result = 1
+        result = prime * result + hash(self.group)
+        result = prime * result + hash(self.name)
+        tags_hash = hash(frozenset(self.tags.items())) if self.tags else 0
+        result = prime * result + tags_hash
+        self._hash = result
+        return result
+
+    def __eq__(self, other):
+        if self is other:
+            return True
+        if other is None:
+            return False
+        return (type(self) == type(other) and
+                self.group == other.group and
+                self.name == other.name and
+                self.tags == other.tags)
+
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
+    def __str__(self):
+        return 'MetricName(name=%s, group=%s, description=%s, tags=%s)' % (
+            self.name, self.group, self.description, self.tags)
--- a/kafka/metrics/metrics.py
+++ b/kafka/metrics/metrics.py
@@ -0,0 +1,257 @@
+import logging
+import sys
+import time
+import threading
+
+from kafka.metrics import AnonMeasurable, KafkaMetric, MetricConfig, MetricName
+from kafka.metrics.stats import Sensor
+
+logger = logging.getLogger(__name__)
+
+
+class Metrics(object):
+    """
+    A registry of sensors and metrics.
+
+    A metric is a named, numerical measurement. A sensor is a handle to
+    record numerical measurements as they occur. Each Sensor has zero or
+    more associated metrics. For example a Sensor might represent message
+    sizes and we might associate with this sensor a metric for the average,
+    maximum, or other statistics computed off the sequence of message sizes
+    that are recorded by the sensor.
+
+    Usage looks something like this:
+        # set up metrics:
+        metrics = Metrics() # the global repository of metrics and sensors
+        sensor = metrics.sensor('message-sizes')
+        metric_name = MetricName('message-size-avg', 'producer-metrics')
+        sensor.add(metric_name, Avg())
+        metric_name = MetricName('message-size-max', 'producer-metrics')
+        sensor.add(metric_name, Max())
+
+        # as messages are sent we record the sizes
+        sensor.record(message_size);
+    """
+    def __init__(self, default_config=None, reporters=None,
+                 enable_expiration=False):
+        """
+        Create a metrics repository with a default config, given metric
+        reporters and the ability to expire eligible sensors
+
+        Arguments:
+            default_config (MetricConfig, optional): The default config
+            reporters (list of AbstractMetricsReporter, optional):
+                The metrics reporters
+            enable_expiration (bool, optional): true if the metrics instance
+                can garbage collect inactive sensors, false otherwise
+        """
+        self._lock = threading.RLock()
+        self._config = default_config or MetricConfig()
+        self._sensors = {}
+        self._metrics = {}
+        self._children_sensors = {}
+        self._reporters = reporters or []
+        for reporter in self._reporters:
+            reporter.init([])
+
+        if enable_expiration:
+            def expire_loop():
+                while True:
+                    # delay 30 seconds
+                    time.sleep(30)
+                    self.ExpireSensorTask.run(self)
+            metrics_scheduler = threading.Thread(target=expire_loop)
+            # Creating a daemon thread to not block shutdown
+            metrics_scheduler.daemon = True
+            metrics_scheduler.start()
+
+        self.add_metric(self.metric_name('count', 'kafka-metrics-count',
+                                         'total number of registered metrics'),
+                        AnonMeasurable(lambda config, now: len(self._metrics)))
+
+    @property
+    def config(self):
+        return self._config
+
+    @property
+    def metrics(self):
+        """
+        Get all the metrics currently maintained and indexed by metricName
+        """
+        return self._metrics
+
+    def metric_name(self, name, group, description='', tags=None):
+        """
+        Create a MetricName with the given name, group, description and tags,
+        plus default tags specified in the metric configuration.
+        Tag in tags takes precedence if the same tag key is specified in
+        the default metric configuration.
+
+        Arguments:
+            name (str): The name of the metric
+            group (str): logical group name of the metrics to which this
+                metric belongs
+            description (str, optional): A human-readable description to
+                include in the metric
+            tags (dict, optionals): additional key/value attributes of
+                the metric
+        """
+        combined_tags = dict(self.config.tags)
+        combined_tags.update(tags or {})
+        return MetricName(name, group, description, combined_tags)
+
+    def get_sensor(self, name):
+        """
+        Get the sensor with the given name if it exists
+
+        Arguments:
+            name (str): The name of the sensor
+
+        Returns:
+            Sensor: The sensor or None if no such sensor exists
+        """
+        if not name:
+            raise ValueError('name must be non-empty')
+        return self._sensors.get(name, None)
+
+    def sensor(self, name, config=None,
+               inactive_sensor_expiration_time_seconds=sys.maxsize,
+               parents=None):
+        """
+        Get or create a sensor with the given unique name and zero or
+        more parent sensors. All parent sensors will receive every value
+        recorded with this sensor.
+
+        Arguments:
+            name (str): The name of the sensor
+            config (MetricConfig, optional): A default configuration to use
+                for this sensor for metrics that don't have their own config
+            inactive_sensor_expiration_time_seconds (int, optional):
+                If no value if recorded on the Sensor for this duration of
+                time, it is eligible for removal
+            parents (list of Sensor): The parent sensors
+
+        Returns:
+            Sensor: The sensor that is created
+        """
+        sensor = self.get_sensor(name)
+        if sensor:
+            return sensor
+
+        with self._lock:
+            sensor = self.get_sensor(name)
+            if not sensor:
+                sensor = Sensor(self, name, parents, config or self.config,
+                                inactive_sensor_expiration_time_seconds)
+                self._sensors[name] = sensor
+                if parents:
+                    for parent in parents:
+                        children = self._children_sensors.get(parent)
+                        if not children:
+                            children = []
+                            self._children_sensors[parent] = children
+                        children.append(sensor)
+                logger.debug('Added sensor with name %s', name)
+            return sensor
+
+    def remove_sensor(self, name):
+        """
+        Remove a sensor (if it exists), associated metrics and its children.
+
+        Arguments:
+            name (str): The name of the sensor to be removed
+        """
+        sensor = self._sensors.get(name)
+        if sensor:
+            child_sensors = None
+            with sensor._lock:
+                with self._lock:
+                    val = self._sensors.pop(name, None)
+                    if val and val == sensor:
+                        for metric in sensor.metrics:
+                            self.remove_metric(metric.metric_name)
+                        logger.debug('Removed sensor with name %s', name)
+                        child_sensors = self._children_sensors.pop(sensor, None)
+            if child_sensors:
+                for child_sensor in child_sensors:
+                    self.remove_sensor(child_sensor.name)
+
+    def add_metric(self, metric_name, measurable, config=None):
+        """
+        Add a metric to monitor an object that implements measurable.
+        This metric won't be associated with any sensor.
+        This is a way to expose existing values as metrics.
+
+        Arguments:
+            metricName (MetricName): The name of the metric
+            measurable (AbstractMeasurable): The measurable that will be
+                measured by this metric
+            config (MetricConfig, optional): The configuration to use when
+                measuring this measurable
+        """
+        # NOTE there was a lock here, but i don't think it's needed
+        metric = KafkaMetric(metric_name, measurable, config or self.config)
+        self.register_metric(metric)
+
+    def remove_metric(self, metric_name):
+        """
+        Remove a metric if it exists and return it. Return None otherwise.
+        If a metric is removed, `metric_removal` will be invoked
+        for each reporter.
+
+        Arguments:
+            metric_name (MetricName): The name of the metric
+
+        Returns:
+            KafkaMetric: the removed `KafkaMetric` or None if no such
+                metric exists
+        """
+        with self._lock:
+            metric = self._metrics.pop(metric_name, None)
+            if metric:
+                for reporter in self._reporters:
+                    reporter.metric_removal(metric)
+            return metric
+
+    def add_reporter(self, reporter):
+        """Add a MetricReporter"""
+        with self._lock:
+            reporter.init(list(self.metrics.values()))
+            self._reporters.append(reporter)
+
+    def register_metric(self, metric):
+        with self._lock:
+            if metric.metric_name in self.metrics:
+                raise ValueError('A metric named "%s" already exists, cannot'
+                                 ' register another one.' % metric.metric_name)
+            self.metrics[metric.metric_name] = metric
+            for reporter in self._reporters:
+                reporter.metric_change(metric)
+
+    class ExpireSensorTask(object):
+        """
+        This iterates over every Sensor and triggers a remove_sensor
+        if it has expired. Package private for testing
+        """
+        @staticmethod
+        def run(metrics):
+            items = list(metrics._sensors.items())
+            for name, sensor in items:
+                # remove_sensor also locks the sensor object. This is fine
+                # because synchronized is reentrant. There is however a minor
+                # race condition here. Assume we have a parent sensor P and
+                # child sensor C. Calling record on C would cause a record on
+                # P as well. So expiration time for P == expiration time for C.
+                # If the record on P happens via C just after P is removed,
+                # that will cause C to also get removed. Since the expiration
+                # time is typically high it is not expected to be a significant
+                # concern and thus not necessary to optimize
+                with sensor._lock:
+                    if sensor.has_expired():
+                        logger.debug('Removing expired sensor %s', name)
+                        metrics.remove_sensor(name)
+
+    def close(self):
+        """Close this metrics repository."""
+        for reporter in self._reporters:
+            reporter.close()
--- a/kafka/metrics/metrics_reporter.py
+++ b/kafka/metrics/metrics_reporter.py
@@ -0,0 +1,55 @@
+import abc
+
+
+class AbstractMetricsReporter(object):
+    """
+    An abstract class to allow things to listen as new metrics
+    are created so they can be reported.
+    """
+    __metaclass__ = abc.ABCMeta
+
+    @abc.abstractmethod
+    def init(self, metrics):
+        """
+        This is called when the reporter is first registered
+        to initially register all existing metrics
+
+        Arguments:
+            metrics (list of KafkaMetric): All currently existing metrics
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def metric_change(self, metric):
+        """
+        This is called whenever a metric is updated or added
+
+        Arguments:
+            metric (KafkaMetric)
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def metric_removal(self, metric):
+        """
+        This is called whenever a metric is removed
+
+        Arguments:
+            metric (KafkaMetric)
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def configure(self, configs):
+        """
+        Configure this class with the given key-value pairs
+
+        Arguments:
+            configs (dict of {str, ?})
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def close(self):
+        """Called when the metrics repository is closed."""
+        raise NotImplementedError
--- a/kafka/metrics/quota.py
+++ b/kafka/metrics/quota.py
@@ -0,0 +1,39 @@
+class Quota(object):
+    """An upper or lower bound for metrics"""
+    def __init__(self, bound, is_upper):
+        self._bound = bound
+        self._upper = is_upper
+
+    @staticmethod
+    def upper_bound(upper_bound):
+        return Quota(upper_bound, True)
+
+    @staticmethod
+    def lower_bound(lower_bound):
+        return Quota(lower_bound, False)
+
+    def is_upper_bound(self):
+        return self._upper
+
+    @property
+    def bound(self):
+        return self._bound
+
+    def is_acceptable(self, value):
+        return ((self.is_upper_bound() and value <= self.bound) or
+                (not self.is_upper_bound() and value >= self.bound))
+
+    def __hash__(self):
+        prime = 31
+        result = prime + self.bound
+        return prime * result + self.is_upper_bound()
+
+    def __eq__(self, other):
+        if self is other:
+            return True
+        return (type(self) == type(other) and
+                self.bound == other.bound and
+                self.is_upper_bound() == other.is_upper_bound())
+
+    def __ne__(self, other):
+        return not self.__eq__(other)
--- a/kafka/metrics/stat.py
+++ b/kafka/metrics/stat.py
@@ -0,0 +1,21 @@
+import abc
+
+
+class AbstractStat(object):
+    """
+    An AbstractStat is a quantity such as average, max, etc that is computed
+    off the stream of updates to a sensor
+    """
+    __metaclass__ = abc.ABCMeta
+
+    @abc.abstractmethod
+    def record(self, config, value, time_ms):
+        """
+        Record the given value
+
+        Arguments:
+            config (MetricConfig): The configuration to use for this metric
+            value (float): The value to record
+            timeMs (int): The POSIX time in milliseconds this value occurred
+        """
+        raise NotImplementedError
--- a/kafka/metrics/stats/init.py
+++ b/kafka/metrics/stats/init.py
@@ -0,0 +1,15 @@
+from .avg import Avg
+from .count import Count
+from .histogram import Histogram
+from .max_stat import Max
+from .min_stat import Min
+from .percentile import Percentile
+from .percentiles import Percentiles
+from .rate import Rate
+from .sensor import Sensor
+from .total import Total
+
+__all__ = [
+    'Avg', 'Count', 'Histogram', 'Max', 'Min', 'Percentile', 'Percentiles',
+    'Rate', 'Sensor', 'Total'
+]
--- a/kafka/metrics/stats/avg.py
+++ b/kafka/metrics/stats/avg.py
@@ -0,0 +1,22 @@
+from kafka.metrics.stats.sampled_stat import AbstractSampledStat
+
+
+class Avg(AbstractSampledStat):
+    """
+    An AbstractSampledStat that maintains a simple average over its samples.
+    """
+    def __init__(self):
+        super(Avg, self).__init__(0.0)
+
+    def update(self, sample, config, value, now):
+        sample.value += value
+
+    def combine(self, samples, config, now):
+        total_sum = 0
+        total_count = 0
+        for sample in samples:
+            total_sum += sample.value
+            total_count += sample.event_count
+        if not total_count:
+            return 0
+        return float(total_sum) / total_count
--- a/kafka/metrics/stats/count.py
+++ b/kafka/metrics/stats/count.py
@@ -0,0 +1,15 @@
+from kafka.metrics.stats.sampled_stat import AbstractSampledStat
+
+
+class Count(AbstractSampledStat):
+    """
+    An AbstractSampledStat that maintains a simple count of what it has seen.
+    """
+    def __init__(self):
+        super(Count, self).__init__(0.0)
+
+    def update(self, sample, config, value, now):
+        sample.value += 1.0
+
+    def combine(self, samples, config, now):
+        return float(sum(sample.value for sample in samples))
--- a/kafka/metrics/stats/histogram.py
+++ b/kafka/metrics/stats/histogram.py
@@ -0,0 +1,93 @@
+import math
+
+
+class Histogram(object):
+    def __init__(self, bin_scheme):
+        self._hist = [0.0] * bin_scheme.bins
+        self._count = 0.0
+        self._bin_scheme = bin_scheme
+
+    def record(self, value):
+        self._hist[self._bin_scheme.to_bin(value)] += 1.0
+        self._count += 1.0
+
+    def value(self, quantile):
+        if self._count == 0.0:
+            return float('NaN')
+        _sum = 0.0
+        quant = float(quantile)
+        for i, value in enumerate(self._hist[:-1]):
+            _sum += value
+            if _sum / self._count > quant:
+                return self._bin_scheme.from_bin(i)
+        return float('inf')
+
+    @property
+    def counts(self):
+        return self._hist
+
+    def clear(self):
+        for i in range(self._hist):
+            self._hist[i] = 0.0
+        self._count = 0
+
+    def __str__(self):
+        values = ['%.10f:%.0f' % (self._bin_scheme.from_bin(i), value) for
+                  i, value in enumerate(self._hist[:-1])]
+        values.append('%s:%s' % (float('inf'), self._hist[-1]))
+        return '{%s}' % ','.join(values)
+
+    class ConstantBinScheme(object):
+        def __init__(self, bins, min_val, max_val):
+            if bins < 2:
+                raise ValueError('Must have at least 2 bins.')
+            self._min = float(min_val)
+            self._max = float(max_val)
+            self._bins = int(bins)
+            self._bucket_width = (max_val - min_val) / (bins - 2)
+
+        @property
+        def bins(self):
+            return self._bins
+
+        def from_bin(self, b):
+            if b == 0:
+                return float('-inf')
+            elif b == self._bins - 1:
+                return float('inf')
+            else:
+                return self._min + (b - 1) * self._bucket_width
+
+        def to_bin(self, x):
+            if x < self._min:
+                return 0
+            elif x > self._max:
+                return self._bins - 1
+            else:
+                return int(((x - self._min) / self._bucket_width) + 1)
+
+    class LinearBinScheme(object):
+        def __init__(self, num_bins, max_val):
+            self._bins = num_bins
+            self._max = max_val
+            self._scale = max_val / (num_bins * (num_bins - 1) / 2)
+
+        @property
+        def bins(self):
+            return self._bins
+
+        def from_bin(self, b):
+            if b == self._bins - 1:
+                return float('inf')
+            else:
+                unscaled = (b * (b + 1.0)) / 2.0
+                return unscaled * self._scale
+
+        def to_bin(self, x):
+            if x < 0.0:
+                raise ValueError('Values less than 0.0 not accepted.')
+            elif x > self._max:
+                return self._bins - 1
+            else:
+                scaled = x / self._scale
+                return int(-0.5 + math.sqrt(2.0 * scaled + 0.25))
--- a/kafka/metrics/stats/max_stat.py
+++ b/kafka/metrics/stats/max_stat.py
@@ -0,0 +1,15 @@
+from kafka.metrics.stats.sampled_stat import AbstractSampledStat
+
+
+class Max(AbstractSampledStat):
+    """An AbstractSampledStat that gives the max over its samples."""
+    def __init__(self):
+        super(Max, self).__init__(float('-inf'))
+
+    def update(self, sample, config, value, now):
+        sample.value = max(sample.value, value)
+
+    def combine(self, samples, config, now):
+        if not samples:
+            return float('-inf')
+        return float(max(sample.value for sample in samples))
--- a/kafka/metrics/stats/min_stat.py
+++ b/kafka/metrics/stats/min_stat.py
@@ -0,0 +1,17 @@
+import sys
+
+from kafka.metrics.stats.sampled_stat import AbstractSampledStat
+
+
+class Min(AbstractSampledStat):
+    """An AbstractSampledStat that gives the min over its samples."""
+    def __init__(self):
+        super(Min, self).__init__(float(sys.maxsize))
+
+    def update(self, sample, config, value, now):
+        sample.value = min(sample.value, value)
+
+    def combine(self, samples, config, now):
+        if not samples:
+            return float(sys.maxsize)
+        return float(min(sample.value for sample in samples))
--- a/kafka/metrics/stats/percentile.py
+++ b/kafka/metrics/stats/percentile.py
@@ -0,0 +1,12 @@
+class Percentile(object):
+    def __init__(self, metric_name, percentile):
+        self._metric_name = metric_name
+        self._percentile = float(percentile)
+
+    @property
+    def name(self):
+        return self._metric_name
+
+    @property
+    def percentile(self):
+        return self._percentile
--- a/kafka/metrics/stats/percentiles.py
+++ b/kafka/metrics/stats/percentiles.py
@@ -0,0 +1,72 @@
+from kafka.metrics import AnonMeasurable, NamedMeasurable
+from kafka.metrics.compound_stat import AbstractCompoundStat
+from kafka.metrics.stats import Histogram
+from kafka.metrics.stats.sampled_stat import AbstractSampledStat
+
+
+class BucketSizing(object):
+    CONSTANT = 0
+    LINEAR = 1
+
+
+class Percentiles(AbstractSampledStat, AbstractCompoundStat):
+    """A compound stat that reports one or more percentiles"""
+    def __init__(self, size_in_bytes, bucketing, max_val, min_val=0.0,
+                 percentiles=None):
+        super(Percentiles, self).__init__(0.0)
+        self._percentiles = percentiles or []
+        self._buckets = int(size_in_bytes / 4)
+        if bucketing == BucketSizing.CONSTANT:
+            self._bin_scheme = Histogram.ConstantBinScheme(self._buckets,
+                                                           min_val, max_val)
+        elif bucketing == BucketSizing.LINEAR:
+            if min_val != 0.0:
+                raise ValueError('Linear bucket sizing requires min_val'
+                                 ' to be 0.0.')
+            self.bin_scheme = Histogram.LinearBinScheme(self._buckets, max_val)
+        else:
+            ValueError('Unknown bucket type: %s' % bucketing)
+
+    def stats(self):
+        measurables = []
+
+        def make_measure_fn(pct):
+            return lambda config, now: self.value(config, now,
+                                                  pct / 100.0)
+
+        for percentile in self._percentiles:
+            measure_fn = make_measure_fn(percentile.percentile)
+            stat = NamedMeasurable(percentile.name, AnonMeasurable(measure_fn))
+            measurables.append(stat)
+        return measurables
+
+    def value(self, config, now, quantile):
+        self.purge_obsolete_samples(config, now)
+        count = sum(sample.event_count for sample in self._samples)
+        if count == 0.0:
+            return float('NaN')
+        sum_val = 0.0
+        quant = float(quantile)
+        for b in range(self._buckets):
+            for sample in self._samples:
+                assert type(sample) is self.HistogramSample
+                hist = sample.histogram.counts
+                sum_val += hist[b]
+                if sum_val / count > quant:
+                    return self._bin_scheme.from_bin(b)
+        return float('inf')
+
+    def combine(self, samples, config, now):
+        return self.value(config, now, 0.5)
+
+    def new_sample(self, time_ms):
+        return Percentiles.HistogramSample(self._bin_scheme, time_ms)
+
+    def update(self, sample, config, value, time_ms):
+        assert type(sample) is self.HistogramSample
+        sample.histogram.record(value)
+
+    class HistogramSample(AbstractSampledStat.Sample):
+        def __init__(self, scheme, now):
+            super(Percentiles.HistogramSample, self).__init__(0.0, now)
+            self.histogram = Histogram(scheme)
--- a/kafka/metrics/stats/rate.py
+++ b/kafka/metrics/stats/rate.py
@@ -0,0 +1,115 @@
+from kafka.metrics.measurable_stat import AbstractMeasurableStat
+from kafka.metrics.stats.sampled_stat import AbstractSampledStat
+
+
+class TimeUnit(object):
+    _names = {
+        'nanosecond': 0,
+        'microsecond': 1,
+        'millisecond': 2,
+        'second': 3,
+        'minute': 4,
+        'hour':  5,
+        'day': 6,
+    }
+
+    NANOSECONDS = _names['nanosecond']
+    MICROSECONDS = _names['microsecond']
+    MILLISECONDS = _names['millisecond']
+    SECONDS = _names['second']
+    MINUTES = _names['minute']
+    HOURS = _names['hour']
+    DAYS = _names['day']
+
+    @staticmethod
+    def get_name(time_unit):
+        return TimeUnit._names[time_unit]
+
+
+class Rate(AbstractMeasurableStat):
+    """
+    The rate of the given quantity. By default this is the total observed
+    over a set of samples from a sampled statistic divided by the elapsed
+    time over the sample windows. Alternative AbstractSampledStat
+    implementations can be provided, however, to record the rate of
+    occurrences (e.g. the count of values measured over the time interval)
+    or other such values.
+    """
+    def __init__(self, time_unit=TimeUnit.SECONDS, sampled_stat=None):
+        self._stat = sampled_stat or SampledTotal()
+        self._unit = time_unit
+
+    def unit_name(self):
+        return TimeUnit.get_name(self._unit)
+
+    def record(self, config, value, time_ms):
+        self._stat.record(config, value, time_ms)
+
+    def measure(self, config, now):
+        value = self._stat.measure(config, now)
+        return float(value) / self.convert(self.window_size(config, now))
+
+    def window_size(self, config, now):
+        # purge old samples before we compute the window size
+        self._stat.purge_obsolete_samples(config, now)
+
+        """
+        Here we check the total amount of time elapsed since the oldest
+        non-obsolete window. This give the total window_size of the batch
+        which is the time used for Rate computation. However, there is
+        an issue if we do not have sufficient data for e.g. if only
+        1 second has elapsed in a 30 second window, the measured rate
+        will be very high. Hence we assume that the elapsed time is
+        always N-1 complete windows plus whatever fraction of the final
+        window is complete.
+
+        Note that we could simply count the amount of time elapsed in
+        the current window and add n-1 windows to get the total time,
+        but this approach does not account for sleeps. AbstractSampledStat
+        only creates samples whenever record is called, if no record is
+        called for a period of time that time is not accounted for in
+        window_size and produces incorrect results.
+        """
+        total_elapsed_time_ms = now - self._stat.oldest(now).last_window_ms
+        # Check how many full windows of data we have currently retained
+        num_full_windows = int(total_elapsed_time_ms / config.time_window_ms)
+        min_full_windows = config.samples - 1
+
+        # If the available windows are less than the minimum required,
+        # add the difference to the totalElapsedTime
+        if num_full_windows < min_full_windows:
+            total_elapsed_time_ms += ((min_full_windows - num_full_windows) *
+                                      config.time_window_ms)
+
+        return total_elapsed_time_ms
+
+    def convert(self, time_ms):
+        if self._unit == TimeUnit.NANOSECONDS:
+            return time_ms * 1000.0 * 1000.0
+        elif self._unit == TimeUnit.MICROSECONDS:
+            return time_ms * 1000.0
+        elif self._unit == TimeUnit.MILLISECONDS:
+            return time_ms
+        elif self._unit == TimeUnit.SECONDS:
+            return time_ms / 1000.0
+        elif self._unit == TimeUnit.MINUTES:
+            return time_ms / (60.0 * 1000.0)
+        elif self._unit == TimeUnit.HOURS:
+            return time_ms / (60.0 * 60.0 * 1000.0)
+        elif self._unit == TimeUnit.DAYS:
+            return time_ms / (24.0 * 60.0 * 60.0 * 1000.0)
+        else:
+            raise ValueError('Unknown unit: %s' % self._unit)
+
+
+class SampledTotal(AbstractSampledStat):
+    def __init__(self, initial_value=None):
+        if initial_value is not None:
+            raise ValueError('initial_value cannot be set on SampledTotal')
+        super(SampledTotal, self).__init__(0.0)
+
+    def update(self, sample, config, value, time_ms):
+        sample.value += value
+
+    def combine(self, samples, config, now):
+        return float(sum(sample.value for sample in samples))
--- a/kafka/metrics/stats/sampled_stat.py
+++ b/kafka/metrics/stats/sampled_stat.py
@@ -0,0 +1,99 @@
+import abc
+
+from kafka.metrics.measurable_stat import AbstractMeasurableStat
+
+
+class AbstractSampledStat(AbstractMeasurableStat):
+    """
+    An AbstractSampledStat records a single scalar value measured over
+    one or more samples. Each sample is recorded over a configurable
+    window. The window can be defined by number of events or elapsed
+    time (or both, if both are given the window is complete when
+    *either* the event count or elapsed time criterion is met).
+
+    All the samples are combined to produce the measurement. When a
+    window is complete the oldest sample is cleared and recycled to
+    begin recording the next sample.
+
+    Subclasses of this class define different statistics measured
+    using this basic pattern.
+    """
+    __metaclass__ = abc.ABCMeta
+
+    def __init__(self, initial_value):
+        self._initial_value = initial_value
+        self._samples = []
+        self._current = 0
+
+    @abc.abstractmethod
+    def update(self, sample, config, value, time_ms):
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def combine(self, samples, config, now):
+        raise NotImplementedError
+
+    def record(self, config, value, time_ms):
+        sample = self.current(time_ms)
+        if sample.is_complete(time_ms, config):
+            sample = self._advance(config, time_ms)
+        self.update(sample, config, float(value), time_ms)
+        sample.event_count += 1
+
+    def new_sample(self, time_ms):
+        return self.Sample(self._initial_value, time_ms)
+
+    def measure(self, config, now):
+        self.purge_obsolete_samples(config, now)
+        return float(self.combine(self._samples, config, now))
+
+    def current(self, time_ms):
+        if not self._samples:
+            self._samples.append(self.new_sample(time_ms))
+        return self._samples[self._current]
+
+    def oldest(self, now):
+        if not self._samples:
+            self._samples.append(self.new_sample(now))
+        oldest = self._samples[0]
+        for sample in self._samples[1:]:
+            if sample.last_window_ms < oldest.last_window_ms:
+                oldest = sample
+        return oldest
+
+    def purge_obsolete_samples(self, config, now):
+        """
+        Timeout any windows that have expired in the absence of any events
+        """
+        expire_age = config.samples * config.time_window_ms
+        for sample in self._samples:
+            if now - sample.last_window_ms >= expire_age:
+                sample.reset(now)
+
+    def _advance(self, config, time_ms):
+        self._current = (self._current + 1) % config.samples
+        if self._current >= len(self._samples):
+            sample = self.new_sample(time_ms)
+            self._samples.append(sample)
+            return sample
+        else:
+            sample = self.current(time_ms)
+            sample.reset(time_ms)
+            return sample
+
+    class Sample(object):
+
+        def __init__(self, initial_value, now):
+            self.initial_value = initial_value
+            self.event_count = 0
+            self.last_window_ms = now
+            self.value = initial_value
+
+        def reset(self, now):
+            self.event_count = 0
+            self.last_window_ms = now
+            self.value = self.initial_value
+
+        def is_complete(self, time_ms, config):
+            return (time_ms - self.last_window_ms >= config.time_window_ms or
+                    self.event_count >= config.event_window)
--- a/kafka/metrics/stats/sensor.py
+++ b/kafka/metrics/stats/sensor.py
@@ -0,0 +1,132 @@
+import threading
+import time
+
+from kafka.errors import QuotaViolationError
+from kafka.metrics import KafkaMetric
+
+
+class Sensor(object):
+    """
+    A sensor applies a continuous sequence of numerical values
+    to a set of associated metrics. For example a sensor on
+    message size would record a sequence of message sizes using
+    the `record(double)` api and would maintain a set
+    of metrics about request sizes such as the average or max.
+    """
+    def __init__(self, registry, name, parents, config,
+                 inactive_sensor_expiration_time_seconds):
+        if not name:
+            raise ValueError('name must be non-empty')
+        self._lock = threading.RLock()
+        self._registry = registry
+        self._name = name
+        self._parents = parents or []
+        self._metrics = []
+        self._stats = []
+        self._config = config
+        self._inactive_sensor_expiration_time_ms = (
+            inactive_sensor_expiration_time_seconds * 1000)
+        self._last_record_time = time.time() * 1000
+        self._check_forest(set())
+
+    def _check_forest(self, sensors):
+        """Validate that this sensor doesn't end up referencing itself."""
+        if self in sensors:
+            raise ValueError('Circular dependency in sensors: %s is its own'
+                             'parent.' % self.name)
+        sensors.add(self)
+        for parent in self._parents:
+            parent._check_forest(sensors)
+
+    @property
+    def name(self):
+        """
+        The name this sensor is registered with.
+        This name will be unique among all registered sensors.
+        """
+        return self._name
+
+    @property
+    def metrics(self):
+        return tuple(self._metrics)
+
+    def record(self, value=1.0, time_ms=None):
+        """
+        Record a value at a known time.
+        Arguments:
+            value (double): The value we are recording
+            time_ms (int): The current POSIX time in milliseconds
+
+        Raises:
+            QuotaViolationException: if recording this value moves a
+                metric beyond its configured maximum or minimum bound
+        """
+        now = time.time() * 1000
+        if time_ms is None:
+            time_ms = now
+        self._last_record_time = now
+        with self._lock:  # XXX high volume, might be performance issue
+            # increment all the stats
+            for stat in self._stats:
+                stat.record(self._config, value, time_ms)
+            self._check_quotas(time_ms)
+        for parent in self._parents:
+            parent.record(value, time_ms)
+
+    def _check_quotas(self, time_ms):
+        """
+        Check if we have violated our quota for any metric that
+        has a configured quota
+        """
+        for metric in self._metrics:
+            if metric.config and metric.config.quota:
+                value = metric.value(time_ms)
+                if not metric.config.quota.is_acceptable(value):
+                    raise QuotaViolationError('(%s) violated quota. Actual: '
+                                              '(%d), Threshold: (%d)' %
+                                              (metric.metric_name,
+                                               metric.config.quota.bound,
+                                               value))
+
+    def add_compound(self, compound_stat, config=None):
+        """
+        Register a compound statistic with this sensor which
+        yields multiple measurable quantities (like a histogram)
+
+        Arguments:
+            stat (AbstractCompoundStat): The stat to register
+            config (MetricConfig): The configuration for this stat.
+                If None then the stat will use the default configuration
+                for this sensor.
+        """
+        if not compound_stat:
+            raise ValueError('compound stat must be non-empty')
+        self._stats.append(compound_stat)
+        for named_measurable in compound_stat.stats():
+            metric = KafkaMetric(named_measurable.name, named_measurable.stat,
+                                 config or self._config)
+            self._registry.register_metric(metric)
+            self._metrics.append(metric)
+
+    def add(self, metric_name, stat, config=None):
+        """
+        Register a metric with this sensor
+
+        Arguments:
+            metric_name (MetricName): The name of the metric
+            stat (AbstractMeasurableStat): The statistic to keep
+            config (MetricConfig): A special configuration for this metric.
+                If None use the sensor default configuration.
+        """
+        with self._lock:
+            metric = KafkaMetric(metric_name, stat, config or self._config)
+            self._registry.register_metric(metric)
+            self._metrics.append(metric)
+            self._stats.append(stat)
+
+    def has_expired(self):
+        """
+        Return True if the Sensor is eligible for removal due to inactivity.
+        """
+        return ((time.time() * 1000 - self._last_record_time) >
+                self._inactive_sensor_expiration_time_ms)
--- a/kafka/metrics/stats/total.py
+++ b/kafka/metrics/stats/total.py
@@ -0,0 +1,13 @@
+from kafka.metrics.measurable_stat import AbstractMeasurableStat
+
+
+class Total(AbstractMeasurableStat):
+    """An un-windowed cumulative total maintained over all time."""
+    def __init__(self, value=0.0):
+        self._total = value
+
+    def record(self, config, value, now):
+        self._total += value
+
+    def measure(self, config, now):
+        return float(self._total)
--- a/test/test_coordinator.py
+++ b/test/test_coordinator.py
@@ -1,5 +1,6 @@
 # pylint: skip-file
 from __future__ import absolute_import
+import time

 import pytest

@@ -14,6 +15,7 @@ from kafka.coordinator.protocol import (
    ConsumerProtocolMemberMetadata, ConsumerProtocolMemberAssignment)
 import kafka.errors as Errors
 from kafka.future import Future
+from kafka.metrics import Metrics
 from kafka.protocol.commit import (
    OffsetCommitRequest, OffsetCommitResponse,
    OffsetFetchRequest, OffsetFetchResponse)
@@ -23,12 +25,14 @@ from kafka.util import WeakMethod

@pytest.fixture
 def coordinator(conn):
-    return ConsumerCoordinator(KafkaClient(), SubscriptionState())
+    return ConsumerCoordinator(KafkaClient(), SubscriptionState(), Metrics(),
+                               'consumer')


 def test_init(conn):
    cli = KafkaClient()
-    coordinator = ConsumerCoordinator(cli, SubscriptionState())
+    coordinator = ConsumerCoordinator(cli, SubscriptionState(), Metrics(),
+                                      'consumer')

    # metadata update on init 
    assert cli.cluster._need_update is True
@@ -38,6 +42,7 @@ def test_init(conn):
@pytest.mark.parametrize("api_version", [(0, 8, 0), (0, 8, 1), (0, 8, 2), (0, 9)])
 def test_autocommit_enable_api_version(conn, api_version):
    coordinator = ConsumerCoordinator(KafkaClient(), SubscriptionState(),
+                                      Metrics(), 'consumer',
                                      enable_auto_commit=True,
                                      group_id='foobar',
                                      api_version=api_version)
@@ -354,6 +359,7 @@ def test_maybe_auto_commit_offsets_sync(mocker, api_version, group_id, enable,
    mock_warn = mocker.patch('kafka.coordinator.consumer.log.warning')
    mock_exc = mocker.patch('kafka.coordinator.consumer.log.exception')
    coordinator = ConsumerCoordinator(KafkaClient(), SubscriptionState(),
+                                      Metrics(), 'consumer',
                                      api_version=api_version,
                                      enable_auto_commit=enable,
                                      group_id=group_id)
@@ -441,7 +447,7 @@ def test_send_offset_commit_request_failure(patched_coord, offsets):
    assert future.exception is error


-def test_send_offset_commit_request_success(patched_coord, offsets):
+def test_send_offset_commit_request_success(mocker, patched_coord, offsets):
    _f = Future()
    patched_coord._client.send.return_value = _f
    future = patched_coord._send_offset_commit_request(offsets)
@@ -449,7 +455,7 @@ def test_send_offset_commit_request_success(patched_coord, offsets):
    response = OffsetCommitResponse[0]([('foobar', [(0, 0), (1, 0)])])
    _f.success(response)
    patched_coord._handle_offset_commit_response.assert_called_with(
-        offsets, future, response) 
+        offsets, future, mocker.ANY, response)


@pytest.mark.parametrize('response,error,dead,reassign', [
@@ -478,10 +484,11 @@ def test_send_offset_commit_request_success(patched_coord, offsets):
    (OffsetCommitResponse[0]([('foobar', [(0, 29), (1, 29)])]),
     Errors.TopicAuthorizationFailedError, False, False),
 ])
-def test_handle_offset_commit_response(patched_coord, offsets,
+def test_handle_offset_commit_response(mocker, patched_coord, offsets,
                                       response, error, dead, reassign):
    future = Future()
-    patched_coord._handle_offset_commit_response(offsets, future, response)
+    patched_coord._handle_offset_commit_response(offsets, future, time.time(),
+                                                 response)
    assert isinstance(future.exception, error)
    assert patched_coord.coordinator_id is (None if dead else 0)
    assert patched_coord._subscription.needs_partition_assignment is reassign
--- a/test/test_fetcher.py
+++ b/test/test_fetcher.py
@@ -8,6 +8,7 @@ from kafka.consumer.fetcher import Fetcher
 from kafka.consumer.subscription_state import SubscriptionState
 import kafka.errors as Errors
 from kafka.future import Future
+from kafka.metrics import Metrics
 from kafka.protocol.fetch import FetchRequest
 from kafka.structs import TopicPartition, OffsetAndMetadata

@@ -29,7 +30,7 @@ def fetcher(client, subscription_state):
    subscription_state.assign_from_subscribed(assignment)
    for tp in assignment:
        subscription_state.seek(tp, 0)
-    return Fetcher(client, subscription_state)
+    return Fetcher(client, subscription_state, Metrics(), 'test_fetcher')


 def test_init_fetches(fetcher, mocker):
--- a/test/test_metrics.py
+++ b/test/test_metrics.py
@@ -0,0 +1,499 @@
+import sys
+import time
+
+import pytest
+
+from kafka.errors import QuotaViolationError
+from kafka.metrics import DictReporter, MetricConfig, MetricName, Metrics, Quota
+from kafka.metrics.measurable import AbstractMeasurable
+from kafka.metrics.stats import (Avg, Count, Max, Min, Percentile, Percentiles,
+                                 Rate, Total)
+from kafka.metrics.stats.percentiles import BucketSizing
+from kafka.metrics.stats.rate import TimeUnit
+
+EPS = 0.000001
+
+
+@pytest.fixture
+def time_keeper():
+    return TimeKeeper()
+
+
+@pytest.fixture
+def config():
+    return MetricConfig()
+
+
+@pytest.fixture
+def reporter():
+    return DictReporter()
+
+
+@pytest.fixture
+def metrics(request, config, reporter):
+    metrics = Metrics(config, [reporter], enable_expiration=True)
+    request.addfinalizer(lambda: metrics.close())
+    return metrics
+
+
+def test_MetricName():
+    # The Java test only cover the differences between the deprecated
+    # constructors, so I'm skipping them but doing some other basic testing.
+
+    # In short, metrics should be equal IFF their name, group, and tags are
+    # the same. Descriptions do not matter.
+    name1 = MetricName('name', 'group', 'A metric.', {'a': 1, 'b': 2})
+    name2 = MetricName('name', 'group', 'A description.', {'a': 1, 'b': 2})
+    assert name1 == name2
+
+    name1 = MetricName('name', 'group', tags={'a': 1, 'b': 2})
+    name2 = MetricName('name', 'group', tags={'a': 1, 'b': 2})
+    assert name1 == name2
+
+    name1 = MetricName('foo', 'group')
+    name2 = MetricName('name', 'group')
+    assert name1 != name2
+
+    name1 = MetricName('name', 'foo')
+    name2 = MetricName('name', 'group')
+    assert name1 != name2
+
+    # name and group must be non-empty. Everything else is optional.
+    with pytest.raises(Exception):
+        MetricName('', 'group')
+    with pytest.raises(Exception):
+        MetricName('name', None)
+    # tags must be a dict if supplied
+    with pytest.raises(Exception):
+        MetricName('name', 'group', tags=set())
+
+    # Because of the implementation of __eq__ and __hash__, the values of
+    # a MetricName cannot be mutable.
+    tags = {'a': 1}
+    name = MetricName('name', 'group', 'description', tags=tags)
+    with pytest.raises(AttributeError):
+        name.name = 'new name'
+    with pytest.raises(AttributeError):
+        name.group = 'new name'
+    with pytest.raises(AttributeError):
+        name.tags = {}
+    # tags is a copy, so the instance isn't altered
+    name.tags['b'] = 2
+    assert name.tags == tags
+
+
+def test_simple_stats(mocker, time_keeper, config, metrics):
+    mocker.patch('time.time', side_effect=time_keeper.time)
+
+    measurable = ConstantMeasurable()
+
+    metrics.add_metric(metrics.metric_name('direct.measurable', 'grp1',
+                                            'The fraction of time an appender waits for space allocation.'),
+                        measurable)
+    sensor = metrics.sensor('test.sensor')
+    sensor.add(metrics.metric_name('test.avg', 'grp1'), Avg())
+    sensor.add(metrics.metric_name('test.max', 'grp1'), Max())
+    sensor.add(metrics.metric_name('test.min', 'grp1'), Min())
+    sensor.add(metrics.metric_name('test.rate', 'grp1'), Rate(TimeUnit.SECONDS))
+    sensor.add(metrics.metric_name('test.occurences', 'grp1'),Rate(TimeUnit.SECONDS, Count()))
+    sensor.add(metrics.metric_name('test.count', 'grp1'), Count())
+    percentiles = [Percentile(metrics.metric_name('test.median', 'grp1'), 50.0),
+                Percentile(metrics.metric_name('test.perc99_9', 'grp1'), 99.9)]
+    sensor.add_compound(Percentiles(100, BucketSizing.CONSTANT, 100, -100,
+                        percentiles=percentiles))
+
+    sensor2 = metrics.sensor('test.sensor2')
+    sensor2.add(metrics.metric_name('s2.total', 'grp1'), Total())
+    sensor2.record(5.0)
+
+    sum_val = 0
+    count = 10
+    for i in range(count):
+        sensor.record(i)
+        sum_val += i
+
+    # prior to any time passing
+    elapsed_secs = (config.time_window_ms * (config.samples - 1)) / 1000.0
+    assert abs(count / elapsed_secs -
+            metrics.metrics.get(metrics.metric_name('test.occurences', 'grp1')).value()) \
+            < EPS, 'Occurrences(0...%d) = %f' % (count, count / elapsed_secs)
+
+    # pretend 2 seconds passed...
+    sleep_time_seconds = 2.0
+    time_keeper.sleep(sleep_time_seconds)
+    elapsed_secs += sleep_time_seconds
+
+    assert abs(5.0 - metrics.metrics.get(metrics.metric_name('s2.total', 'grp1')).value()) \
+            < EPS, 's2 reflects the constant value'
+    assert abs(4.5 - metrics.metrics.get(metrics.metric_name('test.avg', 'grp1')).value()) \
+            < EPS, 'Avg(0...9) = 4.5'
+    assert abs((count - 1) - metrics.metrics.get(metrics.metric_name('test.max', 'grp1')).value()) \
+            < EPS, 'Max(0...9) = 9'
+    assert abs(0.0 - metrics.metrics.get(metrics.metric_name('test.min', 'grp1')).value()) \
+            < EPS, 'Min(0...9) = 0'
+    assert abs((sum_val / elapsed_secs) - metrics.metrics.get(metrics.metric_name('test.rate', 'grp1')).value()) \
+            < EPS, 'Rate(0...9) = 1.40625'
+    assert abs((count / elapsed_secs) - metrics.metrics.get(metrics.metric_name('test.occurences', 'grp1')).value()) \
+            < EPS, 'Occurrences(0...%d) = %f' % (count, count / elapsed_secs)
+    assert abs(count - metrics.metrics.get(metrics.metric_name('test.count', 'grp1')).value()) \
+            < EPS, 'Count(0...9) = 10'
+
+
+def test_hierarchical_sensors(metrics):
+    parent1 = metrics.sensor('test.parent1')
+    parent1.add(metrics.metric_name('test.parent1.count', 'grp1'), Count())
+    parent2 = metrics.sensor('test.parent2')
+    parent2.add(metrics.metric_name('test.parent2.count', 'grp1'), Count())
+    child1 = metrics.sensor('test.child1', parents=[parent1, parent2])
+    child1.add(metrics.metric_name('test.child1.count', 'grp1'), Count())
+    child2 = metrics.sensor('test.child2', parents=[parent1])
+    child2.add(metrics.metric_name('test.child2.count', 'grp1'), Count())
+    grandchild = metrics.sensor('test.grandchild', parents=[child1])
+    grandchild.add(metrics.metric_name('test.grandchild.count', 'grp1'), Count())
+
+    # increment each sensor one time
+    parent1.record()
+    parent2.record()
+    child1.record()
+    child2.record()
+    grandchild.record()
+
+    p1 = parent1.metrics[0].value()
+    p2 = parent2.metrics[0].value()
+    c1 = child1.metrics[0].value()
+    c2 = child2.metrics[0].value()
+    gc = grandchild.metrics[0].value()
+
+    # each metric should have a count equal to one + its children's count
+    assert 1.0 == gc
+    assert 1.0 + gc == c1
+    assert 1.0 == c2
+    assert 1.0 + c1 == p2
+    assert 1.0 + c1 + c2 == p1
+    assert [child1, child2] == metrics._children_sensors.get(parent1)
+    assert [child1] == metrics._children_sensors.get(parent2)
+    assert metrics._children_sensors.get(grandchild) is None
+
+
+def test_bad_sensor_hierarchy(metrics):
+    parent = metrics.sensor('parent')
+    child1 = metrics.sensor('child1', parents=[parent])
+    child2 = metrics.sensor('child2', parents=[parent])
+
+    with pytest.raises(ValueError):
+        metrics.sensor('gc', parents=[child1, child2])
+
+
+def test_remove_sensor(metrics):
+    size = len(metrics.metrics)
+    parent1 = metrics.sensor('test.parent1')
+    parent1.add(metrics.metric_name('test.parent1.count', 'grp1'), Count())
+    parent2 = metrics.sensor('test.parent2')
+    parent2.add(metrics.metric_name('test.parent2.count', 'grp1'), Count())
+    child1 = metrics.sensor('test.child1', parents=[parent1, parent2])
+    child1.add(metrics.metric_name('test.child1.count', 'grp1'), Count())
+    child2 = metrics.sensor('test.child2', parents=[parent2])
+    child2.add(metrics.metric_name('test.child2.count', 'grp1'), Count())
+    grandchild1 = metrics.sensor('test.gchild2', parents=[child2])
+    grandchild1.add(metrics.metric_name('test.gchild2.count', 'grp1'), Count())
+
+    sensor = metrics.get_sensor('test.parent1')
+    assert sensor is not None
+    metrics.remove_sensor('test.parent1')
+    assert metrics.get_sensor('test.parent1') is None
+    assert metrics.metrics.get(metrics.metric_name('test.parent1.count', 'grp1')) is None
+    assert metrics.get_sensor('test.child1') is None
+    assert metrics._children_sensors.get(sensor) is None
+    assert metrics.metrics.get(metrics.metric_name('test.child1.count', 'grp1')) is None
+
+    sensor = metrics.get_sensor('test.gchild2')
+    assert sensor is not None
+    metrics.remove_sensor('test.gchild2')
+    assert metrics.get_sensor('test.gchild2') is None
+    assert metrics._children_sensors.get(sensor) is None
+    assert metrics.metrics.get(metrics.metric_name('test.gchild2.count', 'grp1')) is None
+
+    sensor = metrics.get_sensor('test.child2')
+    assert sensor is not None
+    metrics.remove_sensor('test.child2')
+    assert metrics.get_sensor('test.child2') is None
+    assert metrics._children_sensors.get(sensor) is None
+    assert metrics.metrics.get(metrics.metric_name('test.child2.count', 'grp1')) is None
+
+    sensor = metrics.get_sensor('test.parent2')
+    assert sensor is not None
+    metrics.remove_sensor('test.parent2')
+    assert metrics.get_sensor('test.parent2') is None
+    assert metrics._children_sensors.get(sensor) is None
+    assert metrics.metrics.get(metrics.metric_name('test.parent2.count', 'grp1')) is None
+
+    assert size == len(metrics.metrics)
+
+
+def test_remove_inactive_metrics(mocker, time_keeper, metrics):
+    mocker.patch('time.time', side_effect=time_keeper.time)
+
+    s1 = metrics.sensor('test.s1', None, 1)
+    s1.add(metrics.metric_name('test.s1.count', 'grp1'), Count())
+
+    s2 = metrics.sensor('test.s2', None, 3)
+    s2.add(metrics.metric_name('test.s2.count', 'grp1'), Count())
+
+    purger = Metrics.ExpireSensorTask
+    purger.run(metrics)
+    assert metrics.get_sensor('test.s1') is not None, \
+            'Sensor test.s1 must be present'
+    assert metrics.metrics.get(metrics.metric_name('test.s1.count', 'grp1')) is not None, \
+            'MetricName test.s1.count must be present'
+    assert metrics.get_sensor('test.s2') is not None, \
+            'Sensor test.s2 must be present'
+    assert metrics.metrics.get(metrics.metric_name('test.s2.count', 'grp1')) is not None, \
+            'MetricName test.s2.count must be present'
+
+    time_keeper.sleep(1.001)
+    purger.run(metrics)
+    assert metrics.get_sensor('test.s1') is None, \
+            'Sensor test.s1 should have been purged'
+    assert metrics.metrics.get(metrics.metric_name('test.s1.count', 'grp1')) is None, \
+            'MetricName test.s1.count should have been purged'
+    assert metrics.get_sensor('test.s2') is not None, \
+            'Sensor test.s2 must be present'
+    assert metrics.metrics.get(metrics.metric_name('test.s2.count', 'grp1')) is not None, \
+            'MetricName test.s2.count must be present'
+
+    # record a value in sensor s2. This should reset the clock for that sensor.
+    # It should not get purged at the 3 second mark after creation
+    s2.record()
+
+    time_keeper.sleep(2)
+    purger.run(metrics)
+    assert metrics.get_sensor('test.s2') is not None, \
+            'Sensor test.s2 must be present'
+    assert metrics.metrics.get(metrics.metric_name('test.s2.count', 'grp1')) is not None, \
+            'MetricName test.s2.count must be present'
+
+    # After another 1 second sleep, the metric should be purged
+    time_keeper.sleep(1)
+    purger.run(metrics)
+    assert metrics.get_sensor('test.s1') is None, \
+            'Sensor test.s2 should have been purged'
+    assert metrics.metrics.get(metrics.metric_name('test.s1.count', 'grp1')) is None, \
+            'MetricName test.s2.count should have been purged'
+
+    # After purging, it should be possible to recreate a metric
+    s1 = metrics.sensor('test.s1', None, 1)
+    s1.add(metrics.metric_name('test.s1.count', 'grp1'), Count())
+    assert metrics.get_sensor('test.s1') is not None, \
+        'Sensor test.s1 must be present'
+    assert metrics.metrics.get(metrics.metric_name('test.s1.count', 'grp1')) is not None, \
+            'MetricName test.s1.count must be present'
+
+
+def test_remove_metric(metrics):
+    size = len(metrics.metrics)
+    metrics.add_metric(metrics.metric_name('test1', 'grp1'), Count())
+    metrics.add_metric(metrics.metric_name('test2', 'grp1'), Count())
+
+    assert metrics.remove_metric(metrics.metric_name('test1', 'grp1')) is not None
+    assert metrics.metrics.get(metrics.metric_name('test1', 'grp1')) is None
+    assert metrics.metrics.get(metrics.metric_name('test2', 'grp1')) is not None
+
+    assert metrics.remove_metric(metrics.metric_name('test2', 'grp1')) is not None
+    assert metrics.metrics.get(metrics.metric_name('test2', 'grp1')) is None
+
+    assert size == len(metrics.metrics)
+
+
+def test_event_windowing(mocker, time_keeper):
+    mocker.patch('time.time', side_effect=time_keeper.time)
+
+    count = Count()
+    config = MetricConfig(event_window=1, samples=2)
+    count.record(config, 1.0, time_keeper.ms())
+    count.record(config, 1.0, time_keeper.ms())
+    assert 2.0 == count.measure(config, time_keeper.ms())
+    count.record(config, 1.0, time_keeper.ms())  # first event times out
+    assert 2.0 == count.measure(config, time_keeper.ms())
+
+
+def test_time_windowing(mocker, time_keeper):
+    mocker.patch('time.time', side_effect=time_keeper.time)
+
+    count = Count()
+    config = MetricConfig(time_window_ms=1, samples=2)
+    count.record(config, 1.0, time_keeper.ms())
+    time_keeper.sleep(.001)
+    count.record(config, 1.0, time_keeper.ms())
+    assert 2.0 == count.measure(config, time_keeper.ms())
+    time_keeper.sleep(.001)
+    count.record(config, 1.0, time_keeper.ms())  # oldest event times out
+    assert 2.0 == count.measure(config, time_keeper.ms())
+
+
+def test_old_data_has_no_effect(mocker, time_keeper):
+    mocker.patch('time.time', side_effect=time_keeper.time)
+
+    max_stat = Max()
+    min_stat = Min()
+    avg_stat = Avg()
+    count_stat = Count()
+    window_ms = 100
+    samples = 2
+    config = MetricConfig(time_window_ms=window_ms, samples=samples)
+    max_stat.record(config, 50, time_keeper.ms())
+    min_stat.record(config, 50, time_keeper.ms())
+    avg_stat.record(config, 50, time_keeper.ms())
+    count_stat.record(config, 50, time_keeper.ms())
+
+    time_keeper.sleep(samples * window_ms / 1000.0)
+    assert float('-inf') == max_stat.measure(config, time_keeper.ms())
+    assert float(sys.maxsize) == min_stat.measure(config, time_keeper.ms())
+    assert 0.0 == avg_stat.measure(config, time_keeper.ms())
+    assert 0 == count_stat.measure(config, time_keeper.ms())
+
+
+def test_duplicate_MetricName(metrics):
+    metrics.sensor('test').add(metrics.metric_name('test', 'grp1'), Avg())
+    with pytest.raises(ValueError):
+        metrics.sensor('test2').add(metrics.metric_name('test', 'grp1'), Total())
+
+
+def test_Quotas(metrics):
+    sensor = metrics.sensor('test')
+    sensor.add(metrics.metric_name('test1.total', 'grp1'), Total(),
+               MetricConfig(quota=Quota.upper_bound(5.0)))
+    sensor.add(metrics.metric_name('test2.total', 'grp1'), Total(),
+               MetricConfig(quota=Quota.lower_bound(0.0)))
+    sensor.record(5.0)
+    with pytest.raises(QuotaViolationError):
+        sensor.record(1.0)
+
+    assert abs(6.0 - metrics.metrics.get(metrics.metric_name('test1.total', 'grp1')).value()) \
+            < EPS
+
+    sensor.record(-6.0)
+    with pytest.raises(QuotaViolationError):
+        sensor.record(-1.0)
+
+
+def test_Quotas_equality():
+    quota1 = Quota.upper_bound(10.5)
+    quota2 = Quota.lower_bound(10.5)
+    assert quota1 != quota2, 'Quota with different upper values should not be equal'
+
+    quota3 = Quota.lower_bound(10.5)
+    assert quota2 == quota3, 'Quota with same upper and bound values should be equal'
+
+
+def test_Percentiles(metrics):
+    buckets = 100
+    _percentiles = [
+        Percentile(metrics.metric_name('test.p25', 'grp1'), 25),
+        Percentile(metrics.metric_name('test.p50', 'grp1'), 50),
+        Percentile(metrics.metric_name('test.p75', 'grp1'), 75),
+    ]
+    percs = Percentiles(4 * buckets, BucketSizing.CONSTANT, 100.0, 0.0,
+                        percentiles=_percentiles)
+    config = MetricConfig(event_window=50, samples=2)
+    sensor = metrics.sensor('test', config)
+    sensor.add_compound(percs)
+    p25 = metrics.metrics.get(metrics.metric_name('test.p25', 'grp1'))
+    p50 = metrics.metrics.get(metrics.metric_name('test.p50', 'grp1'))
+    p75 = metrics.metrics.get(metrics.metric_name('test.p75', 'grp1'))
+
+    # record two windows worth of sequential values
+    for i in range(buckets):
+        sensor.record(i)
+
+    assert abs(p25.value() - 25) < 1.0
+    assert abs(p50.value() - 50) < 1.0
+    assert abs(p75.value() - 75) < 1.0
+
+    for i in range(buckets):
+        sensor.record(0.0)
+
+    assert p25.value() < 1.0
+    assert p50.value() < 1.0
+    assert p75.value() < 1.0
+
+def test_rate_windowing(mocker, time_keeper, metrics):
+    mocker.patch('time.time', side_effect=time_keeper.time)
+
+    # Use the default time window. Set 3 samples
+    config = MetricConfig(samples=3)
+    sensor = metrics.sensor('test.sensor', config)
+    sensor.add(metrics.metric_name('test.rate', 'grp1'), Rate(TimeUnit.SECONDS))
+
+    sum_val = 0
+    count = config.samples - 1
+    # Advance 1 window after every record
+    for i in range(count):
+        sensor.record(100)
+        sum_val += 100
+        time_keeper.sleep(config.time_window_ms / 1000.0)
+
+    # Sleep for half the window.
+    time_keeper.sleep(config.time_window_ms / 2.0 / 1000.0)
+
+    # prior to any time passing
+    elapsed_secs = (config.time_window_ms * (config.samples - 1) + config.time_window_ms / 2.0) / 1000.0
+
+    kafka_metric = metrics.metrics.get(metrics.metric_name('test.rate', 'grp1'))
+    assert abs((sum_val / elapsed_secs) - kafka_metric.value()) < EPS, \
+            'Rate(0...2) = 2.666'
+    assert abs(elapsed_secs - (kafka_metric.measurable.window_size(config, time.time() * 1000) / 1000.0)) \
+            < EPS, 'Elapsed Time = 75 seconds'
+
+
+def test_reporter(metrics):
+    reporter = DictReporter()
+    foo_reporter = DictReporter(prefix='foo')
+    metrics.add_reporter(reporter)
+    metrics.add_reporter(foo_reporter)
+    sensor = metrics.sensor('kafka.requests')
+    sensor.add(metrics.metric_name('pack.bean1.avg', 'grp1'), Avg())
+    sensor.add(metrics.metric_name('pack.bean2.total', 'grp2'), Total())
+    sensor2 = metrics.sensor('kafka.blah')
+    sensor2.add(metrics.metric_name('pack.bean1.some', 'grp1'), Total())
+    sensor2.add(metrics.metric_name('pack.bean2.some', 'grp1',
+                                    tags={'a': 42, 'b': 'bar'}), Total())
+
+    # kafka-metrics-count > count is the total number of metrics and automatic
+    expected = {
+        'kafka-metrics-count': {'count': 5.0},
+        'grp2': {'pack.bean2.total': 0.0},
+        'grp1': {'pack.bean1.avg': 0.0, 'pack.bean1.some': 0.0},
+        'grp1.a=42,b=bar': {'pack.bean2.some': 0.0},
+    }
+    assert expected == reporter.snapshot()
+
+    for key in list(expected.keys()):
+        metrics = expected.pop(key)
+        expected['foo.%s' % key] = metrics
+    assert expected == foo_reporter.snapshot()
+
+
+class ConstantMeasurable(AbstractMeasurable):
+    _value = 0.0
+
+    def measure(self, config, now):
+        return self._value
+
+
+class TimeKeeper(object):
+    """
+    A clock that you can manually advance by calling sleep
+    """
+    def __init__(self, auto_tick_ms=0):
+        self._millis = time.time() * 1000
+        self._auto_tick_ms = auto_tick_ms
+
+    def time(self):
+        return self.ms() / 1000.0
+
+    def ms(self):
+        self.sleep(self._auto_tick_ms)
+        return self._millis
+
+    def sleep(self, seconds):
+        self._millis += (seconds * 1000)