Reactive stream spec violation when using command timeout

[martin-tarjanyi]

Bug Report

Related issue: #1274

Current Behavior

When a RedisCommandTimeoutException happens it is possible (depending on CPU task scheduling) that the timeout error will be triggered after the underlying command is completed thus violating reactive spec. Futhermore, this error causes the DefaultEventExecutor to terminate which leaves most subsequent Redis commands in a stuck state when publishOnScheduler(true).

Stack trace

Thread=[lettuce-eventExecutorLoop-5-7] Logger=io.netty.util.concurrent.SingleThreadEventExecutor Type=WARN Unexpected exception from an event executor: 
reactor.core.Exceptions$BubblingException: io.lettuce.core.RedisCommandTimeoutException: Command timed out after 100 millisecond(s)
	at reactor.core.Exceptions.bubble(Exceptions.java:173) ~[reactor-core-3.3.9.RELEASE.jar!/:3.3.9.RELEASE]
	at reactor.core.publisher.Operators.onErrorDropped(Operators.java:635) ~[reactor-core-3.3.9.RELEASE.jar!/:3.3.9.RELEASE]
	at reactor.core.publisher.MonoNext$NextSubscriber.onError(MonoNext.java:83) ~[reactor-core-3.3.9.RELEASE.jar!/:3.3.9.RELEASE]
	at io.lettuce.core.RedisPublisher$OnComplete.run(RedisPublisher.java:1094) ~[lettuce-core-5.3.3.RELEASE.jar!/:5.3.3.RELEASE]
	at io.netty.util.concurrent.DefaultEventExecutor.run(DefaultEventExecutor.java:66) ~[netty-common-4.1.51.Final.jar!/:4.1.51.Final]
	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989) [netty-common-4.1.51.Final.jar!/:4.1.51.Final]

Input Code

https://github.com/martin-tarjanyi/lettuce-executor-reject-repro

Expected behavior/code

No violation of reactive stream spec, no terminated executor, no stuck Redis commands

Environment

• Lettuce version: 5.3.5.RELEASE
• Redis version: any

Possible Solution

As pointed out by @mp911de SubscriptionCommand and CommandWrapper do not ensure single completion. Fixing that will fix this issue.

[mp911de]

That's fixed now.

[martin-tarjanyi]

We appreciate the really quick turnaround. Thank you @mp911de!

[mp911de]

The releases 6.0.2 respective 5.3.6 are now available from Maven Central