Support simple message iteration in Fetcher and new KafkaConsumer

kafka/consumer/fetcher.py

@@ -316,6 +316,55 @@ class Fetcher(object):
                           tp, fetch_offset)
         return dict(drained)
 
+    def __iter__(self):
+        """Iterate over fetched_records"""
+        if self._subscriptions.needs_partition_assignment:
+            raise StopIteration('Subscription needs partition assignment')
+
+        self._raise_if_offset_out_of_range()
+        self._raise_if_unauthorized_topics()
+        self._raise_if_record_too_large()
+
+        while self._records:
+            (fetch_offset, tp, messages) = self._records.popleft()
+
+            if not self._subscriptions.is_assigned(tp):
+                # this can happen when a rebalance happened before
+                # fetched records are returned
+                log.warning("Not returning fetched records for partition %s"
+                          " since it is no longer assigned", tp)
+                continue
+
+            # note that the consumed position should always be available
+            # as long as the partition is still assigned
+            consumed = self._subscriptions.assignment[tp].consumed
+            if not self._subscriptions.is_fetchable(tp):
+                # this can happen when a partition consumption paused before
+                # fetched records are returned
+                log.warning("Not returning fetched records for assigned partition"
+                          " %s since it is no longer fetchable", tp)
+
+                # we also need to reset the fetch positions to pretend we did
+                # not fetch this partition in the previous request at all
+                self._subscriptions.assignment[tp].fetched = consumed
+
+            elif fetch_offset == consumed:
+                # TODO: handle compressed messages
+                for offset, size, msg in messages:
+                    if msg.attributes:
+                        raise Errors.KafkaError('Compressed messages not supported yet')
+                    elif self.config['check_crcs'] and not msg.validate_crc():
+                        raise Errors.InvalidMessageError(msg)
+
+                    self._subscriptions.assignment[tp].consumed = offset + 1
+                    key, value = self._deserialize(msg)
+                    yield ConsumerRecord(tp.topic, tp.partition, offset, key, value)
+            else:
+                # these records aren't next in line based on the last consumed
+                # position, ignore them they must be from an obsolete request
+                log.warning("Ignoring fetched records for %s at offset %s",
+                          tp, fetch_offset)
+
     def _deserialize(self, msg):
         if self.config['key_deserializer']:
             key = self.config['key_deserializer'](msg.key) # pylint: disable-msg=not-callable

kafka/consumer/group.py

@@ -4,6 +4,8 @@ import copy
 import logging
 import time
 
+import six
+
 import kafka.common as Errors
 
 from kafka.client_async import KafkaClient
@@ -565,3 +567,23 @@ class KafkaConsumer(object):
 
         # then do any offset lookups in case some positions are not known
         self._fetcher.update_fetch_positions(partitions)
+
+    def __iter__(self):
+        while True:
+            # records = self._poll_once(self.config['request_timeout_ms'])
+            self._coordinator.ensure_coordinator_known()
+
+            # ensure we have partitions assigned if we expect to
+            if self._subscription.partitions_auto_assigned():
+                self._coordinator.ensure_active_group()
+
+            # fetch positions if we have partitions we're subscribed to that we
+            # don't know the offset for
+            if not self._subscription.has_all_fetch_positions():
+                self._update_fetch_positions(self._subscription.missing_fetch_positions())
+
+            # init any new fetches (won't resend pending fetches)
+            self._fetcher.init_fetches()
+            self._client.poll(self.config['request_timeout_ms'] / 1000.0)
+            for msg in self._fetcher:
+                yield msg