[KAFKA-2143] Replicas get ahead of leader and fail

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.8.2.1
• Fix Version/s: 0.9.0.1
• Component/s: replication
• Assignee: Jiangjie Qin
• Reporter: Evan Huus
• Reviewer: Gwen Shapira
• Created: 23/Apr/15 18:17
• Updated: 10/Feb/17 05:02
• Resolved: 29/Jan/16 04:20

Description

On a cluster of 6 nodes, we recently saw a case where a single under-replicated partition suddenly appeared, replication lag spiked, and network IO spiked. The cluster appeared to recover eventually on its own,

Looking at the logs, the thing which failed was partition 7 of the topic background_queue. It had an ISR of 1,4,3 and its leader at the time was 3. Here are the interesting log lines:

On node 3 (the leader):

[2015-04-23 16:50:05,879] ERROR [Replica Manager on Broker 3]: Error when processing fetch request for partition [background_queue,7] offset 3722949957 from follower with correlation id 148185816. Possible cause: Request for offset 3722949957 but we only have log segments in the range 3648049863 to 3722949955. (kafka.server.ReplicaManager)
[2015-04-23 16:50:05,879] ERROR [Replica Manager on Broker 3]: Error when processing fetch request for partition [background_queue,7] offset 3722949957 from follower with correlation id 156007054. Possible cause: Request for offset 3722949957 but we only have log segments in the range 3648049863 to 3722949955. (kafka.server.ReplicaManager)
[2015-04-23 16:50:13,960] INFO Partition [background_queue,7] on broker 3: Shrinking ISR for partition [background_queue,7] from 1,4,3 to 3 (kafka.cluster.Partition)

Note that both replicas suddenly asked for an offset ahead of the available offsets.

And on nodes 1 and 4 (the replicas) many occurrences of the following:

[2015-04-23 16:50:05,935] INFO Scheduling log segment 3648049863 for log background_queue-7 for deletion. (kafka.log.Log) (edited)

Based on my reading, this looks like the replicas somehow got ahead of the leader, asked for an invalid offset, got confused, and re-replicated the entire topic from scratch to recover (this matches our network graphs, which show 3 sending a bunch of data to 1 and 4).

Taking a stab in the dark at the cause, there appears to be a race condition where replicas can receive a new offset before the leader has committed it and is ready to replicate?

Issue Links

• is duplicated by: KAFKA-2165 ReplicaFetcherThread: data loss on unknown exception