Details
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Bug
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Status: Open
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Major
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Resolution: Unresolved
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2.8.0
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None
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None
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Kafka running on Kubernetes
centos
Description
Our KStream app offset stay stuck on 1 partition after outage possibly when exactly_once is enabled.
Running with KStream 2.8, kafka broker 2.8,
3 brokers.
commands topic is 10 partitions (replication 2, min-insync 2)
command-expiry-store-changelog topic is 10 partitions (replication 2, min-insync 2)
events topic is 10 partitions (replication 2, min-insync 2)
with this topology
Topologies:
Sub-topology: 0 Source: KSTREAM-SOURCE-0000000000 (topics: [commands]) --> KSTREAM-TRANSFORM-0000000001 Processor: KSTREAM-TRANSFORM-0000000001 (stores: []) --> KSTREAM-TRANSFORM-0000000002 <-- KSTREAM-SOURCE-0000000000 Processor: KSTREAM-TRANSFORM-0000000002 (stores: [command-expiry-store]) --> KSTREAM-SINK-0000000003 <-- KSTREAM-TRANSFORM-0000000001 Sink: KSTREAM-SINK-0000000003 (topic: events) <-- KSTREAM-TRANSFORM-0000000002
Attempt 1 at reproducing this issue
Our stream app runs with processing.guarantee exactly_once
After a Kafka test outage where all 3 brokers pod were deleted at the same time,
Brokers restarted and initialized succesfuly.
When restarting the topology above, one of the tasks would never initialize fully, the restore phase would keep outputting this messages every few minutes:
2021-08-16 14:20:33,421 INFO stream-thread [commands-processor-51b0a534-34b6-47a4-bd9c-c57b6ecb8665-StreamThread-1] Restoration in progress for 1 partitions. {commands-processor-expiry-store-changelog-8: position=11775908, end=11775911, totalRestored=2002076} [commands-processor-51b0a534-34b6-47a4-bd9c-c57b6ecb8665-StreamThread-1] (org.apache.kafka.streams.processor.internals.StoreChangelogReader)
Task for partition 8 would never initialize, no more data would be read from the source commands topic for that partition.
In an attempt to recover, we restarted the stream app with stream processing.guarantee back to at_least_once, than it proceed with reading the changelog and restoring partition 8 fully.
But we noticed afterward, for the next hour until we rebuilt the system, that partition 8 from command-expiry-store-changelog would not be cleaned/compacted by the log cleaner/compacter compared to other partitions. (could be unrelated, because we have seen that before)
So we resorted to delete/recreate our command-expiry-store-changelog topic and events topic and regenerate it from the commands, reading from beginning.
Things went back to normal
Attempt 2 at reproducing this issue
kstream runs with exactly-once
We force-deleted all 3 pod running kafka.
After that, one of the partition can’t be restored. (like reported in previous attempt)
For that partition, we noticed these logs on the broker
[2021-08-27 17:45:32,799] INFO [Transaction Marker Channel Manager 1002]: Couldn’t find leader endpoint for partitions Set(__consumer_offsets-11, command-expiry-store-changelog-9) while trying to send transaction markers for commands-processor-0_9, these partitions are likely deleted already and hence can be skipped (kafka.coordinator.transaction.TransactionMarkerChannelManager)
Then
- we stop the kstream app,
- restarted kafka brokers cleanly
- Restarting the Kstream app,
Those logs messages showed up on the kstream app log:
2021-08-27 18:34:42,413 INFO [Consumer clientId=commands-processor-76602c87-f682-4648-859b-8fa9b6b937f3-StreamThread-1-consumer, groupId=commands-processor] The following partitions still have unstable offsets which are not cleared on the broker side: [commands-9], this could be either transactional offsets waiting for completion, or normal offsets waiting for replication after appending to local log [commands-processor-76602c87-f682-4648-859b-8fa9b6b937f3-StreamThread-1] (org.apache.kafka.clients.consumer.internals.ConsumerCoordinator)
This would cause our processor to not consume from that specific source topic-partition.
Deleting downstream topic and replaying data would NOT fix the issue (EXACTLY_ONCE or AT_LEAST_ONCE)
Workaround found:
Deleted the group associated with the processor, and restarted the kstream application, application went on to process data normally. (We have resigned to use AT_LEAST_ONCE for now )
KStream config :
StreamsConfig.RETRY_BACKOFF_MS_CONFIG, 2000 StreamsConfig.REPLICATION_FACTOR_CONFIG, 2 StreamsConfig.COMMIT_INTERVAL_MS_CONFIG, 1000 StreamsConfig.CACHE_MAX_BYTES_BUFFERING_CONFIG, 24MB ConsumerConfig.AUTO_OFFSET_RESET_CONFIG), “earliest” StreamsConfig.PROCESSING_GUARANTEE_CONFIG, StreamsConfig.EXACTLY_ONCE (now AT_LEAST_ONCE) producer.delivery.timeout.ms=120000 consumer.session.timeout.ms=30000 consumer.heartbeat.interval.ms=10000 consumer.max.poll.interval.ms=300000 num.stream.threads=1
Attempt 3
kstream processor now running with at-least-once
reprocess the entire source topic.
Everything runs stable
We force-deleted all 3 pod running kafka.
Then services comes back up but there is that same error on kstream app:
2021-09-03 19:18:39,414 INFO [Consumer clientId=commands-processor-76602c87-f682-4648-859b-8fa9b6b937f3-StreamThread-1-consumer, groupId=commands-processor] The following partitions still have unstable offsets which are not cleared on the broker side: [commands-9], this could be either transactional offsets waiting for completion, or normal offsets waiting for replication after appending to local log
Got it back processing by
- Stopped the kstream app,
- Took notes of the offset
- deleted the group for kstream app
- manually created the same group and set the offset to were they were for each partition.
- restarted the kstream app and processing resumed normally.
Attempt 4
kstream processor running with at-least-once
reprocess the entire source topic.
Everything runs stable
We do a gracefull restart of kafka brokers.
Then services comes back up but there is that same error on kstream app:
2021-09-03 19:18:39,414 INFO [Consumer clientId=commands-processor-76602c87-f682-4648-859b-8fa9b6b937f3-StreamThread-1-consumer, groupId=commands-processor] The following partitions still have unstable offsets which are not cleared on the broker side: [commands-9], this could be either transactional offsets waiting for completion, or normal offsets waiting for replication after appending to local log
Attempt 5
kstream processor running with at-least-once
Changed the source commands topic to min.in-sync-replicas=1 (instead of 2)
reprocess the entire source topic.
Everything runs stable now
We do multiple gracefull restart of kafka brokers.
The kstream processors recovers succesfully, no more unstable offsets warning, no more at-least-one processor stuck .
Notes that our topics are using replication-factor 2, it seems that running with replication-factor 2, min-in-sync 2 is problematic.
We force-deleted all 3 pod running kafka.
Then services comes back up but there is that same error on kstream app:
2021-09-03 19:18:39,414 INFO [Consumer clientId=commands-processor-76602c87-f682-4648-859b-8fa9b6b937f3-StreamThread-1-consumer, groupId=commands-processor] The following partitions still have unstable offsets which are not cleared on the broker side: [commands-9], this could be either transactional offsets waiting for completion, or normal offsets waiting for replication after appending to local log
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