Lucian Ilie created KAFKA-15572:
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Summary: Race condition between future log dir roll and replace
current with future log during alterReplicaLogDirs
Key: KAFKA-15572
URL: https://issues.apache.org/jira/browse/KAFKA-15572
Project: Kafka
Issue Type: Bug
Components: core
Affects Versions: 3.4.1, 3.3.1
Reporter: Lucian Ilie
We are using a Kafka cluster with Zookeeper, deployed on top of Kubernetes,
using banzaicloud/koperator.
We have multiple disks per broker.
We are using Cruise Control remove disk operation in order to aggregate
multiple smaller disks into a single bigger disk.
When we do this, the operation fails apparently randomly with
NoSuchFileException. Attached a sample of logs for the exception and the
previous operations taking place.
Will further detail the reason for this issue.
Say we have 3 brokers:
* broker 101 with disks /kafka-logs1/kafka, /kafka-logs2/kafka and a bigger
disk /new-kafka-logs1/kafka
* broker 201 with same disks
* broker 301 with same disks
When Cruise Control executes a remove disk operation, it calls Kafka
"adminClient.alterReplicaLogDirs(replicaAssignment)" with such an assignment as
to move all data from /kafka-logs1/kafka and /kafka-logs2/kafka to
/new-kafka-logs1/kafka.
During the alter log dir operation, future logs are created, data is moved and
finally the log dir will be renamed from "topic-partition.hash-future" to
"topic-partition". This operation is started in
[UnifiedLog.renameDir|https://github.com/apache/kafka/blob/3.4/core/src/main/scala/kafka/log/UnifiedLog.scala#L713]
and is locked using the UnifiedLog lock. The rename is then delegated to
[LocalLog.renameDir|https://github.com/apache/kafka/blob/3.4/core/src/main/scala/kafka/log/LocalLog.scala#L111-L113].
This is the 1st code that is part of the race condition.
Meanwhile, log dirs can be rolled based on known conditions (e.g. getting
full), which will call
[UnifiedLog.roll|https://github.com/apache/kafka/blob/3.4/core/src/main/scala/kafka/log/UnifiedLog.scala#L1547],
which is locked using the UnifiedLog lock. However, the further delegation to
UnifiedLog.flushUptoOffsetExclusive is not sharing that lock, since it is done
as a scheduled task in a separate thread. This means that further operations
are not locked at UnifiedLog level. The operation is further delegated to
[LocalLog.flush|https://github.com/apache/kafka/blob/3.4/core/src/main/scala/kafka/log/LocalLog.scala#L177],
which will also try to [flush the log
dir|https://github.com/apache/kafka/blob/3.4/core/src/main/scala/kafka/log/LocalLog.scala#L177].
Since the log dir flush does not share the lock with the rename dir operation,
the rename dir operation might succeed in moving the log dir on disk to
"topic-partition", but the LocalLog._dir will remain set to
"topic-partition.hash-future", and when the flush will attempt to flush the
"topic-partition.hash-future" directory, it will throw NoSuchFileException:
"topic-partition.hash-future".
We tested a fix for this on our clusters and will reply with a PR.
Note that this bug replicates for every version since 3.0.0, caused by [this
commit|https://github.com/apache/kafka/commit/db3e5e2c0de367ffcfe4078359d6d208ba722581#diff-eeafed82ed6a8600c397b108787fdf31e03191b0a192774a65c127d0d26edc44R2341]
when flush dir was added.
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