Flaky test: GarbageCollectorTrashEnabledCustomPolicyIT

[dlmarion]

Test name(s)

• GarbageCollectorTrashEnabledCustomPolicyIT.testTrashHadoopEnabledAccumuloEnabled

Describe the failure observed

[ERROR] org.apache.accumulo.test.functional.GarbageCollectorTrashEnabledCustomPolicyIT.testTrashHadoopEnabledAccumuloEnabled  Time elapsed: 18.113 s  <<< FAILURE!
org.opentest4j.AssertionFailedError: expected: <false> but was: <true>
	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.AssertFalse.failNotFalse(AssertFalse.java:63)
	at org.junit.jupiter.api.AssertFalse.assertFalse(AssertFalse.java:36)
	at org.junit.jupiter.api.AssertFalse.assertFalse(AssertFalse.java:31)
	at org.junit.jupiter.api.Assertions.assertFalse(Assertions.java:228)
	at org.apache.accumulo.test.functional.GarbageCollectorTrashEnabledCustomPolicyIT.testTrashHadoopEnabledAccumuloEnabled(GarbageCollectorTrashEnabledCustomPolicyIT.java:96)

Testing Environment:

• Version of this project: 2.1.1-RC1

What have you tried already?
N/A

Additional context
This test passes on other machines, so it's likely a timing issue. Looking at the test, flush(tableName) is called two lines before.

accumulo/test/src/main/java/org/apache/accumulo/test/functional/GarbageCollectorTrashEnabledCustomPolicyIT.java

Lines 94 to 96 in 7c5bbc6

	c.tableOperations().flush(table);
	ArrayList<StoredTabletFile> files1 = getFilesForTable(super.getServerContext(), c, table);
	assertFalse(files1.isEmpty());

This version of flush does not wait for the flush to complete. Instead, I think that flush(tableName, null, null, true) should replace all occurrences of flush(tableName) in the new GarbageCollector tests.

[ctubbsii]

I'd really love to change the behavior of flush to be synchronous, and have a separate flushAsync method.