Fedor Korotkiy created KAFKA-1387:
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Summary: Kafka getting stuck creating ephemeral node it has
already created when two zookeeper sessions are established in a very short
period of time
Key: KAFKA-1387
URL: https://issues.apache.org/jira/browse/KAFKA-1387
Project: Kafka
Issue Type: Bug
Reporter: Fedor Korotkiy
Kafka broker re-registers itself in zookeeper every time handleNewSession()
callback is invoked.
https://github.com/apache/kafka/blob/0.8.1/core/src/main/scala/kafka/server/KafkaHealthcheck.scala
Now imagine the following sequence of events.
1) Zookeeper session reestablishes. handleNewSession() callback is queued by
the zkClient, but not invoked yet.
2) Zookeeper session reestablishes again, queueing callback second time.
3) First callback is invoked, creating /broker/[id] ephemeral path.
4) Second callback is invoked and it tries to create /broker/[id] path using
createEphemeralPathExpectConflictHandleZKBug() function. But the path is
already exists, so createEphemeralPathExpectConflictHandleZKBug() is getting
stuck in the infinite loop.
Seems like controller election code have the same issue.
I'am able to reproduce this issue on the 0.8.1 branch from github using the
following configs.
# zookeeper
tickTime=10
dataDir=/tmp/zk/
clientPort=2101
maxClientCnxns=0
# kafka
broker.id=1
log.dir=/tmp/kafka
zookeeper.connect=localhost:2101
zookeeper.connection.timeout.ms=100
zookeeper.sessiontimeout.ms=100
Just start kafka and zookeeper and then pause zookeeper several times using
Ctrl-Z.
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