Details
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Bug
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Status: Resolved
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Major
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Resolution: Fixed
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None
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Description
Kafka has two configurable compression codecs: the one used by the client (source codec) and the one finally used when storing into the log (target codec). The target codec defaults to KafkaConfig.compressionType and can be dynamically configured through zookeeper.
The GroupCoordinator appends group membership information into the __consumer_offsets topic by:
1. making a message with group membership information
2. making a MessageSet with the single message compressed with the source codec
3. doing a log.append on the MessageSet
Without this patch, KafkaConfig.offsetsTopicCompressionCodec doesn't get propagated to OffsetConfig instantiation, so GroupMetadataManager uses a source codec of NoCompressionCodec when making the MessageSet. Let's say we have enough group information such that the message formed exceeds KafkaConfig.messageMaxBytes before compression but would fall below the threshold after compression using our source codec. Even if we had dynamically configured __consumer_offsets with our favorite compression codec, the log.append will throw RecordTooLargeException during analyzeAndValidateMessageSet since the message was unexpectedly uncompressed instead of having been compressed with the source codec defined by KafkaConfig.offsetsTopicCompressionCodec.
NOTE: even after this issue is resolved, preliminary tests show that LinkedIn will still hit RecordTooLargeException with large groups that consume many topics (like MirrorMakers with wildcard consumption of .*) since fully expanded subscription and assignment state for each member is put into a single record. But this is a first step in the right direction.
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