Fetch previously committed offsets in base consumer class so long as

a group is configured (but document that group must be None for old
servers). This fixes multiprocessor consumer issue that prevented
access to commit offsets if auto_commit is disabled.
Also refactor fetch_last_known_offsets based on KafkaConsumer
While still setting unknown offsets to 0

kafka/consumer/base.py

@@ -7,7 +7,7 @@ from threading import Lock
 import kafka.common
 from kafka.common import (
     OffsetRequest, OffsetCommitRequest, OffsetFetchRequest,
-    UnknownTopicOrPartitionError
+    UnknownTopicOrPartitionError, check_error
 )
 
 from kafka.util import ReentrantTimer
@@ -68,29 +68,42 @@ class Consumer(object):
                                                self.commit)
             self.commit_timer.start()
 
-        if auto_commit:
+        # Set initial offsets
+        if self.group is not None:
             self.fetch_last_known_offsets(partitions)
         else:
             for partition in partitions:
                 self.offsets[partition] = 0
 
+
     def fetch_last_known_offsets(self, partitions=None):
+        if self.group is None:
+            raise ValueError('KafkaClient.group must not be None')
+
         if not partitions:
             partitions = self.client.get_partition_ids_for_topic(self.topic)
 
-        def get_or_init_offset(resp):
-            try:
-                kafka.common.check_error(resp)
-                return resp.offset
-            except UnknownTopicOrPartitionError:
-                return 0
-
         for partition in partitions:
-            req = OffsetFetchRequest(self.topic, partition)
-            (resp,) = self.client.send_offset_fetch_request(self.group, [req],
-                          fail_on_error=False)
-            self.offsets[partition] = get_or_init_offset(resp)
-        self.fetch_offsets = self.offsets.copy()
+            (resp,) = self.client.send_offset_fetch_request(
+                self.group,
+                [OffsetFetchRequest(self.topic, partition)],
+                fail_on_error=False
+            )
+            try:
+                check_error(resp)
+            # API spec says server wont set an error here
+            # but 0.8.1.1 does actually...
+            except UnknownTopicOrPartitionError:
+                pass
+
+            # -1 offset signals no commit is currently stored
+            if resp.offset == -1:
+                self.offsets[partition] = 0
+
+            # Otherwise we committed the stored offset
+            # and need to fetch the next one
+            else:
+                self.offsets[partition] = resp.offset
 
     def commit(self, partitions=None):
         """

kafka/consumer/multiprocess.py

@@ -93,6 +93,8 @@ class MultiProcessConsumer(Consumer):
     Arguments:
         client: a connected KafkaClient
         group: a name for this consumer, used for offset storage and must be unique
+            If you are connecting to a server that does not support offset
+            commit/fetch (any prior to 0.8.1.1), then you *must* set this to None
         topic: the topic to consume
 
     Keyword Arguments:

kafka/consumer/simple.py

@@ -73,6 +73,8 @@ class SimpleConsumer(Consumer):
     Arguments:
         client: a connected KafkaClient
         group: a name for this consumer, used for offset storage and must be unique
+            If you are connecting to a server that does not support offset
+            commit/fetch (any prior to 0.8.1.1), then you *must* set this to None
         topic: the topic to consume
 
     Keyword Arguments:

test/test_consumer_integration.py

@@ -53,6 +53,7 @@ class TestConsumerIntegration(KafkaIntegrationTestCase):
     def consumer(self, **kwargs):
         if os.environ['KAFKA_VERSION'] == "0.8.0":
             # Kafka 0.8.0 simply doesn't support offset requests, so hard code it being off
+            kwargs['group'] = None
             kwargs['auto_commit'] = False
         else:
             kwargs.setdefault('auto_commit', True)
@@ -260,7 +261,9 @@ class TestConsumerIntegration(KafkaIntegrationTestCase):
         self.send_messages(0, range(0, 10))
         self.send_messages(1, range(10, 20))
 
-        consumer = MultiProcessConsumer(self.client, "group1", self.topic,
+        # set group to None and auto_commit to False to avoid interactions w/
+        # offset commit/fetch apis
+        consumer = MultiProcessConsumer(self.client, None, self.topic,
                                         auto_commit=False, iter_timeout=0)
 
         self.assertEqual(consumer.pending(), 20)

test/test_failover_integration.py

@@ -183,7 +183,7 @@ class TestFailover(KafkaIntegrationTestCase):
 
         client = KafkaClient(hosts)
         group = random_string(10)
-        consumer = SimpleConsumer(client, group, topic,
+        consumer = SimpleConsumer(client, None, topic,
                                   partitions=partitions,
                                   auto_commit=False,
                                   iter_timeout=timeout)