[Failing Test]: PulsarIOTest.testRead is flaky #40288

What happened?

PulsarIOTest.testRead fails intermittently in beam_PreCommit_Java_Pulsar_IO_Direct, including on PRs that don't touch the Pulsar read path.

Example run: https://github.com/apache/beam/actions/runs/36177336523/job/108211025016

PulsarIOTest > testRead FAILED
    java.lang.AssertionError: MapElements/Map/ParMultiDo(Anonymous).output: arrays first differed at element [0]; expected:<1> but was:<0>

The test checks that the output arrives in order:

Assert.assertArrayEquals(result.toArray(), new Integer[] {0, 1, 2, 3, 4, 5, 6, 7, 8, 9});

A PCollection has no order, and PAssert passes the elements through a GroupByKey. On a slow runner, the DirectRunner checkpoints the splittable DoFn after about 1s, so the remaining messages come out in a later bundle. The data itself is complete: the error has no "array lengths differed" text, so all 10 elements arrived. Only the order changed. Because the arguments to assertArrayEquals are swapped, "expected:<1>" is actually the first element that arrived.

Proposed fix:

PAssert.that(pcoll).containsInAnyOrder(0, 1, 2, 3, 4, 5, 6, 7, 8, 9);

The order-sensitive assertion was added in #36141, which closed the earlier flake issues #21714 and #21560.

Issue Failure

Failure: Test is flaky

Issue Priority

Priority: 2 (backlog / disabled test but we think the product is healthy)

Issue Components

• Component: Java SDK
• Component: IO connector