[KAFKA-16967] NioEchoServer fails to register connection and causes flaky failure

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 3.9.0
• Component/s: core
• Labels: flaky-test newbie
• Assignee: TengYao Chi
• Reporter: Greg Harris
• Created: 15/Jun/24 00:45
• Updated: 24/Jun/24 13:40
• Resolved: 24/Jun/24 13:40

Description

The NioEchoServer calls Selector#register for new connections. This call can throw exceptions, which then kill the NioEchoServer. This has been observed in the SslTransportLayerTest testUngracefulRemoteCloseDuringHandshake* methods.

Exception in thread "echoserver" java.lang.IllegalStateException: There is already a connection for id 127.0.0.1:40007-127.0.0.1:43710
	at org.apache.kafka.common.network.Selector.ensureNotRegistered(Selector.java:322)
	at org.apache.kafka.common.network.Selector.register(Selector.java:310)
	at org.apache.kafka.common.network.NioEchoServer.run(NioEchoServer.java:229)

This causes the test to fail with essentially a timeout, when the connection is expired for becoming idle unexpectedly:

org.opentest4j.AssertionFailedError: Unexpected channel state EXPIRED ==> expected: <true> but was: <false>
    at org.junit.jupiter.api.AssertionFailureBuilder.build(AssertionFailureBuilder.java:151)
    at org.junit.jupiter.api.AssertionFailureBuilder.buildAndThrow(AssertionFailureBuilder.java:132)
    at org.junit.jupiter.api.AssertTrue.failNotTrue(AssertTrue.java:63)
    at org.junit.jupiter.api.AssertTrue.assertTrue(AssertTrue.java:36)
    at org.junit.jupiter.api.Assertions.assertTrue(Assertions.java:214)
    at org.apache.kafka.common.network.SslTransportLayerTest.testIOExceptionsDuringHandshake(SslTransportLayerTest.java:898)
    at org.apache.kafka.common.network.SslTransportLayerTest.testUngracefulRemoteCloseDuringHandshakeRead(SslTransportLayerTest.java:837)

Instead, the NioEchoServer should handle exceptions from register in a similar fashion to the SocketServer.

Issue Links

• Discovered while testing: KAFKA-15845 Add Junit5 test extension which detects leaked Kafka clients and servers
• links to: GitHub Pull Request #16384