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https://issues.apache.org/jira/browse/HBASE-25905?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17437132#comment-17437132
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chenglei edited comment on HBASE-25905 at 11/2/21, 3:55 AM:
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[~Xiaolin Ha], thank you for reply, for your new assumption, I have some new
problems:
bq.5. When sync complete, the AsyncFSWAL.unackedAppends is cleared partial,
Why {{AsyncFSWAL.unackedAppends is cleared partial}} ? seems the
AsyncFSWAL::consume is single-thread, and there is no opportunity to insert
new {{FSWALEntry}}.
bq. but once sync of writer can only sync no more than
FanOutOneBlockAsyncDFSOutput.maxDataLen bytes.
Seems that even if unsynced byte size is more than
{{FanOutOneBlockAsyncDFSOutput.maxDataLen}}, we could flush them by multiple
packets.
was (Author: comnetwork):
[~Xiaolin Ha], thank you for reply, for your new assumption, I have some new
problems:
bq.5. When sync complete, the AsyncFSWAL.unackedAppends is cleared partial,
Why {{AsyncFSWAL.unackedAppends is cleared partial}} ? seems the
AsyncFSWAL::consume is single-thread, and there is no opportunity to to insert
new {{FSWALEntry}}.
bq. but once sync of writer can only sync no more than
FanOutOneBlockAsyncDFSOutput.maxDataLen bytes.
Seems that even if unsynced byte size is more than
{{FanOutOneBlockAsyncDFSOutput.maxDataLen}}, we could flush them by multiple
packets.
> Shutdown of WAL stuck at waitForSafePoint
> -----------------------------------------
>
> Key: HBASE-25905
> URL: https://issues.apache.org/jira/browse/HBASE-25905
> Project: HBase
> Issue Type: Bug
> Components: regionserver, wal
> Affects Versions: 3.0.0-alpha-1, 2.0.0
> Reporter: Xiaolin Ha
> Assignee: Xiaolin Ha
> Priority: Critical
> Attachments: rs-jstack1, rs-jstack2, wal-stuck-error-logs.png
>
>
> We use the fan-out HDFS OutputStream and AsyncFSWAL on our clusters, but met
> the problem than RS can not exit completely for several hours util manual
> interventions.
> The two jstacks below show that the regionserver thread can waiting
> unlimitedly in both
> AsyncFSWAL#waitForSafePoint()
> {code:java}
> "regionserver/gh-data-hbase-finance08.mt/10.22.179.24:16020" #29 prio=5
> os_prio=0 tid=0x00007fb2feb5c000 nid=0xa92b waiting on condition
> [0x00007f9ccb992000]
> java.lang.Thread.State: WAITING (parking)
> at sun.misc.Unsafe.park(Native Method)
> - parking to wait for <0x00007faea229a9d0> (a
> java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
> at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitUninterruptibly(AbstractQueuedSynchronizer.java:1976)
> at
> org.apache.hadoop.hbase.regionserver.wal.AsyncFSWAL.waitForSafePoint(AsyncFSWAL.java:687)
> at
> org.apache.hadoop.hbase.regionserver.wal.AsyncFSWAL.doShutdown(AsyncFSWAL.java:743)
> at
> org.apache.hadoop.hbase.regionserver.wal.AbstractFSWAL.shutdown(AbstractFSWAL.java:900)
> at
> org.apache.hadoop.hbase.wal.AbstractFSWALProvider.shutdown(AbstractFSWALProvider.java:182)
> at
> org.apache.hadoop.hbase.wal.RegionGroupingProvider.shutdown(RegionGroupingProvider.java:232)
> at
> org.apache.hadoop.hbase.wal.WALFactory.shutdown(WALFactory.java:271)
> at
> org.apache.hadoop.hbase.regionserver.HRegionServer.shutdownWAL(HRegionServer.java:1405)
> at
> org.apache.hadoop.hbase.regionserver.HRegionServer.run(HRegionServer.java:1147)
> at java.lang.Thread.run(Thread.java:745)
> {code}
> and the log roller stuck at waiting for lock
> {code:java}
> "regionserver/gh-data-hbase-finance08.mt/10.22.179.24:16020.logRoller" #322
> daemon prio=5 os_prio=0 tid=0x00007fb2e11a4000 nid=0xa953 waiting on
> condition [0x00007f9cbd9f1000]
> java.lang.Thread.State: WAITING (parking)
> at sun.misc.Unsafe.park(Native Method)
> - parking to wait for <0x00007faea1217048> (a
> java.util.concurrent.locks.ReentrantLock$FairSync)
> at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:870)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1199)
> at
> java.util.concurrent.locks.ReentrantLock$FairSync.lock(ReentrantLock.java:224)
> at
> java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:285)
> at
> org.apache.hadoop.hbase.regionserver.wal.AbstractFSWAL.rollWriter(AbstractFSWAL.java:822)
> at
> org.apache.hadoop.hbase.wal.AbstractWALRoller$RollController.rollWal(AbstractWALRoller.java:269)
> at
> org.apache.hadoop.hbase.wal.AbstractWALRoller.run(AbstractWALRoller.java:186){code}
>
> I think this scenario can cause this problem:
> # The consumer of WAL enters AsyncFSWAL#syncFailed, it will set writer
> broken and request roll writer;
> # Regionserver close, shutdown the wal factory, enter the
> AsyncFSWAL#waitForSafePoint, waiting on ConditionObject readyForRollingCond,
> and current state is broken and waiting for roll;
> # The AbstractFSWAL#rollWriter waiting on the lock of
> AbstractFSWAL.rollWriterLock, which of held by the regionserver thread when
> close();
> # The consumer of WAL enters AsyncFSWAL#syncFailed, but found that writer is
> broken, and skipped to signal the readyForRollingCond;
>
> {code:java}
> private void syncFailed(long epochWhenSync, Throwable error) {
> LOG.warn("sync failed", error);
> boolean shouldRequestLogRoll = true;
> consumeLock.lock();
> try {
> int currentEpochAndState = epochAndState;
> if (epoch(currentEpochAndState) != epochWhenSync ||
> writerBroken(currentEpochAndState)) {
> // this is not the previous writer which means we have already rolled
> the writer.
> // or this is still the current writer, but we have already marked it
> as broken and request
> // a roll.
> return;
> }
> this.epochAndState = currentEpochAndState | 0b10;
> if (waitingRoll(currentEpochAndState)) {
> readyForRolling = true;
> readyForRollingCond.signalAll();
> // this means we have already in the middle of a rollWriter so just
> tell the roller thread
> // that you can continue without requesting an extra log roll.
> shouldRequestLogRoll = false;
> }
> } finally {
> consumeLock.unlock();
> }
> for (Iterator<FSWALEntry> iter = unackedAppends.descendingIterator();
> iter.hasNext();) {
> toWriteAppends.addFirst(iter.next());
> }
> highestUnsyncedTxid = highestSyncedTxid.get();
> if (shouldRequestLogRoll) {
> // request a roll.
> requestLogRoll(ERROR);
> }
> }{code}
>
> Then the regionserver thread stuck at AsyncFSWAL#waitForSafePoint, and never
> exit except manually kill it.
> So we should limit the shutdown time of WAL, to avoid waiting too long for
> the safe point.
>
>
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