[KAFKA-5818] KafkaStreams state transitions not correct

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.11.0.1, 1.0.0
• Fix Version/s: 0.11.0.1, 1.0.0
• Component/s: streams
• Assignee: Matthias J. Sax
• Reporter: Matthias J. Sax
• Created: 31/Aug/17 22:15
• Updated: 04/Sep/17 15:41
• Resolved: 03/Sep/17 22:25

Description

There is a race condition revealed by failing test KafkaStreamsTest#testCannotStartTwise. It fails with:

java.lang.Exception: Unexpected exception, expected<java.lang.IllegalStateException> but was<java.lang.IllegalThreadStateException>

Caused by: java.lang.IllegalThreadStateException
	at java.lang.Thread.start(Thread.java:705)
	at org.apache.kafka.streams.KafkaStreams.start(KafkaStreams.java:590)
	at org.apache.kafka.streams.KafkaStreamsTest.testCannotStartTwice(KafkaStreamsTest.java:251)

The race condition is a follows:

1) test calls KafkaStreams#start() for the first time and state transits from CREATED -> RUNNING
2) First poll triggers a rebalance and StreamThread put KafkaStreams into state REBALANCING
3) before REBALANCING completes, the main test thread calls KafkaStream#start() again. As current state is REBALANCING, the transition to RUNNING is valid and start() does not fail with IllegalStateException but resumes. When it tries to start internal streams, we get IllegalThreadStateException as thread are already running.

Issue Links

• relates to: KAFKA-5820 Remove unneeded synchronized keyword in StreamThread
• links to: GitHub Pull Request #3775
• links to: GitHub Pull Request #3779