[CI] WatchAckTests testAckWithRestart failing

[piergm]

Build scan:
https://gradle-enterprise.elastic.co/s/hhscz5ua4uhk4/tests/:x-pack:plugin:watcher:internalClusterTest/org.elasticsearch.xpack.watcher.test.integration.WatchAckTests/testAckWithRestart

Reproduction line:

./gradlew ':x-pack:plugin:watcher:internalClusterTest' --tests "org.elasticsearch.xpack.watcher.test.integration.WatchAckTests.testAckWithRestart" -Dtests.seed=73EB7E661A7C6841 -Dtests.locale=is-IS -Dtests.timezone=Europe/Kiev -Druntime.java=22

Applicable branches:
main

Reproduces locally?:
No

Failure history:
Failure dashboard for org.elasticsearch.xpack.watcher.test.integration.WatchAckTests#testAckWithRestart

Failure excerpt:

java.lang.AssertionError: 
Expected: is <1L>
     but: was <0L>

  at __randomizedtesting.SeedInfo.seed([73EB7E661A7C6841:FA6354F740F09034]:0)
  at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:18)
  at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:6)
  at org.elasticsearch.test.ESTestCase.assertThat(ESTestCase.java:2259)
  at org.elasticsearch.xpack.watcher.test.integration.WatchAckTests.testAckWithRestart(WatchAckTests.java:229)
  at jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
  at java.lang.reflect.Method.invoke(Method.java:580)
  at com.carrotsearch.randomizedtesting.RandomizedRunner.invoke(RandomizedRunner.java:1758)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$8.evaluate(RandomizedRunner.java:946)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$9.evaluate(RandomizedRunner.java:982)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$10.evaluate(RandomizedRunner.java:996)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.junit.rules.RunRules.evaluate(RunRules.java:20)
  at org.apache.lucene.tests.util.TestRuleSetupTeardownChained$1.evaluate(TestRuleSetupTeardownChained.java:48)
  at org.apache.lucene.tests.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at org.apache.lucene.tests.util.TestRuleThreadAndTestName$1.evaluate(TestRuleThreadAndTestName.java:45)
  at org.apache.lucene.tests.util.TestRuleIgnoreAfterMaxFailures$1.evaluate(TestRuleIgnoreAfterMaxFailures.java:60)
  at org.apache.lucene.tests.util.TestRuleMarkFailure$1.evaluate(TestRuleMarkFailure.java:44)
  at org.junit.rules.RunRules.evaluate(RunRules.java:20)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$StatementRunner.run(ThreadLeakControl.java:390)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl.forkTimeoutingTask(ThreadLeakControl.java:843)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$3.evaluate(ThreadLeakControl.java:490)
  at com.carrotsearch.randomizedtesting.RandomizedRunner.runSingleTest(RandomizedRunner.java:955)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$5.evaluate(RandomizedRunner.java:840)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$6.evaluate(RandomizedRunner.java:891)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$7.evaluate(RandomizedRunner.java:902)
  at org.apache.lucene.tests.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.tests.util.TestRuleStoreClassName$1.evaluate(TestRuleStoreClassName.java:38)
  at com.carrotsearch.randomizedtesting.rules.NoShadowingOrOverridesOnMethodsRule$1.evaluate(NoShadowingOrOverridesOnMethodsRule.java:40)
  at com.carrotsearch.randomizedtesting.rules.NoShadowingOrOverridesOnMethodsRule$1.evaluate(NoShadowingOrOverridesOnMethodsRule.java:40)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.tests.util.TestRuleAssertionsRequired$1.evaluate(TestRuleAssertionsRequired.java:53)
  at org.apache.lucene.tests.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at org.apache.lucene.tests.util.TestRuleMarkFailure$1.evaluate(TestRuleMarkFailure.java:44)
  at org.apache.lucene.tests.util.TestRuleIgnoreAfterMaxFailures$1.evaluate(TestRuleIgnoreAfterMaxFailures.java:60)
  at org.apache.lucene.tests.util.TestRuleIgnoreTestSuites$1.evaluate(TestRuleIgnoreTestSuites.java:47)
  at org.junit.rules.RunRules.evaluate(RunRules.java:20)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$StatementRunner.run(ThreadLeakControl.java:390)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl.lambda$forkTimeoutingTask$0(ThreadLeakControl.java:850)
  at java.lang.Thread.run(Thread.java:1570)

[elasticsearchmachine]

Pinging @elastic/es-data-management (Team:Data Management)

[masseyke]

Possibly another shard-reallocation-related race condition?

  1> [2024-06-13T16:14:04,368][INFO ][o.e.x.w.t.ScheduleTriggerEngineMock] [node_s3] adding watch [_name]
  1> [2024-06-13T16:14:04,421][INFO ][o.e.x.w.WatcherService   ] [node_s5] reloading watcher, reason [new local watcher shard allocation ids], cancelled [0] queued tasks
  1> [2024-06-13T16:14:04,423][INFO ][o.e.x.w.WatcherService   ] [node_s3] reloading watcher, reason [new local watcher shard allocation ids], cancelled [0] queued tasks

[masseyke]

It looks like we reset the stats any time shards move. Given that we see a shard move at this time, it seems pretty likely that that's what has happened here. Unless/until we change stats, the best option might be to just remove this line that's checking stats.

[masseyke]

Looking at the build history for the last 3 months, this test has failed 6 times on 3 different test methods, all b/c the stats returned 0 instead of 1.