[HBASE-25932] TestWALEntryStream#testCleanClosedWALs test is failing. - ASF JIRA

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Details

Type: Bug
Status: Resolved
Priority: Major
Resolution: Fixed
Affects Version/s: 3.0.0-alpha-1, 2.5.0, 2.3.6, 2.4.4
Fix Version/s: 3.0.0-alpha-1, 2.5.0, 2.4.4
Component/s: metrics, Replication, wal
Labels:
None

Description

We are seeing the following test failure. TestWALEntryStream#testCleanClosedWALs
This test was added in ~~HBASE-25924~~. I don't think the test failure has anything to do with the patch in ~~HBASE-25924~~.
Before ~~HBASE-25924~~, we were not monitoring uncleanlyClosedWAL metric. In all the branches, we were not parsing the wal trailer when we close the wal reader inside ReplicationSourceWALReader thread. The root cause was when we add active WAL to ReplicationSourceWALReader, we cache the file size when the wal was being actively written and once the wal was closed and replicated and removed from WALEntryStream, we did reset the ProtobufLogReader object but we didn't update the length of the wal and that was causing EOF errors since it can't find the WALTrailer with the stale wal file length.

The fix applied nicely to branch-1 since we use FSHlog implementation which closes the WAL file sychronously.

But in branch-2 and master, we use AsyncFSWAL implementation and the closing of wal file is done asynchronously (as the name suggests). This is causing the test to fail. Below is the test.

  @Test
  public void testCleanClosedWALs() throws Exception {
    try (WALEntryStream entryStream = new WALEntryStream(
      logQueue, CONF, 0, log, null, logQueue.getMetrics(), fakeWalGroupId)) {
      assertEquals(0, logQueue.getMetrics().getUncleanlyClosedWALs());
      appendToLogAndSync();
      assertNotNull(entryStream.next());
      log.rollWriter();  =======> This does an asynchronous close of wal.
      appendToLogAndSync();
      assertNotNull(entryStream.next());
      assertEquals(0, logQueue.getMetrics().getUncleanlyClosedWALs());
    }
  }

In the above code, when we roll writer, we don't close the old wal file immediately so the ReplicationReader thread is not able to get the updated wal file size and that is throwing EOF errors.
If I add a sleep of few milliseconds (1 ms in my local env) between rollWriter and appendToLogAndSync statement then the test passes but this is not a proper fix since we are working around the race between ReplicationSourceWALReaderThread and closing of WAL file.