[
https://issues.apache.org/jira/browse/HDFS-10943?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16926355#comment-16926355
]
wangcong edited comment on HDFS-10943 at 9/10/19 6:15 AM:
----------------------------------------------------------
[~daryn]，[~kihwal]，[~zhz]，[~hexiaoqiao]，[~yzhangal]
Our log cluster occurs this problem several times.
We use individual cluster to write to yarn logs. But this log cluster crash
serveral times.In the process of viewing logs，We found the same error as this
issue.
To diagnosis this problem ,we deploy HDFS-11306 and HDFS-11292.
When log cluster crash again , diagnostic log as follows:
2019-09-10 03:50:16,403 ERROR org.apache.hadoop.hdfs.server.namenode.FSEditLog:
LastWrittenTxId 5061382841 is expected to be the same as LastSyncedTxId
5061382840
2019-09-10 03:50:16,403 WARN
org.apache.hadoop.hdfs.server.namenode.EditsDoubleBuffer: The edits buffer is
85 bytes long with 1 unflushed transactions.Below is the list of unflushed
transactions
2019-09-10 03:50:16,408 WARN
org.apache.hadoop.hdfs.server.namenode.EditsDoubleBuffer: Unflushed op [0]:
CancelDelegationTokenOp [token=token for yarn: HDFS_DELEGATION_TOKEN
owner=yarn/[email protected], renewer=yarn,
realUser=,issueDate=1567970236988, maxDate=1568575036988,
sequenceNumber=621170591, masterKeyId=108, opcode=OP_CANCEL_DELEGATION_TOKEN,
txid=5061382841]
2019-09-10 03:50:16,409 FATAL
org.apache.hadoop.hdfs.server.namenode.FSEditLog: Error: finalize log segment
5060982535, 5061382841 failed for required journal (JournalAndStream(mgr=QJM to
[10.0.0.1:8001,10.0.0.2:8001,10.0.0.3:8001],stream=QuorumOutputStream starting
at txid 5060982535))
java.io.IOException: FSEditsStream has 85 bytes still to be flushed and cannot
be closed
After deploying patch，namenode crash occurs twice. The op which cause this
problem all is CancelDelegationTokenOp.
was (Author: swingcong):
[~daryn]，[~kihwal]，[~zhz]，[~hexiaoqiao]，[~yzhangal]
Our log cluster occurs this problem several times.
We use individual cluster to write to yarn logs. But this log cluster crash
serveral times.In the process of viewing logs，We found the same error as this
issue.
To diagnosis this problem ,we deploy HDFS-11306 and HDFS-11292.
When log cluster crash again , diagnostic log as follows:
2019-09-10 03:50:16,403 ERROR org.apache.hadoop.hdfs.server.namenode.FSEditLog:
LastWrittenTxId 5061382841 is expected to be the same as LastSyncedTxId
5061382840
2019-09-10 03:50:16,403 WARN
org.apache.hadoop.hdfs.server.namenode.EditsDoubleBuffer: The edits buffer is
85 bytes long with 1 unflushed transactions.Below is the list of unflushed
transactions
2019-09-10 03:50:16,408 WARN
org.apache.hadoop.hdfs.server.namenode.EditsDoubleBuffer: Unflushed op [0]:
CancelDelegationTokenOp [token=token for yarn: HDFS_DELEGATION_TOKEN
owner=yarn/[email protected], renewer=yarn,
realUser=,issueDate=1567970236988, maxDate=1568575036988,
sequenceNumber=621170591, masterKeyId=108, opcode=OP_CANCEL_DELEGATION_TOKEN,
txid=5061382841]
2019-09-10 03:50:16,409 FATAL org.apache.hadoop.hdfs.server.namenode.FSEditLog:
Error: finalize log segment 5060982535, 5061382841 failed for required journal
(JournalAndStream(mgr=QJM to
[10.0.0.1:8001,10.0.0.2:8001,10.0.0.3:8001],stream=QuorumOutputStream starting
at txid 5060982535))
java.io.IOException: FSEditsStream has 85 bytes still to be flushed and cannot
be closed
After deploying patch，namenode crash occurs twice. The op which cause this
problem all is
CancelDelegationTokenOp.
> rollEditLog expects empty EditsDoubleBuffer.bufCurrent which is not guaranteed
> ------------------------------------------------------------------------------
>
> Key: HDFS-10943
> URL: https://issues.apache.org/jira/browse/HDFS-10943
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Yongjun Zhang
> Priority: Major
>
> Per the following trace stack:
> {code}
> FATAL org.apache.hadoop.hdfs.server.namenode.FSEditLog: Error: finalize log
> segment 10562075963, 10562174157 failed for required journal
> (JournalAndStream(mgr=QJM to [0.0.0.1:8485, 0.0.0.2:8485, 0.0.0.3:8485,
> 0.0.0.4:8485, 0.0.0.5:8485], stream=QuorumOutputStream starting at txid
> 10562075963))
> java.io.IOException: FSEditStream has 49708 bytes still to be flushed and
> cannot be closed.
> at
> org.apache.hadoop.hdfs.server.namenode.EditsDoubleBuffer.close(EditsDoubleBuffer.java:66)
> at
> org.apache.hadoop.hdfs.qjournal.client.QuorumOutputStream.close(QuorumOutputStream.java:65)
> at
> org.apache.hadoop.hdfs.server.namenode.JournalSet$JournalAndStream.closeStream(JournalSet.java:115)
> at
> org.apache.hadoop.hdfs.server.namenode.JournalSet$4.apply(JournalSet.java:235)
> at
> org.apache.hadoop.hdfs.server.namenode.JournalSet.mapJournalsAndReportErrors(JournalSet.java:393)
> at
> org.apache.hadoop.hdfs.server.namenode.JournalSet.finalizeLogSegment(JournalSet.java:231)
> at
> org.apache.hadoop.hdfs.server.namenode.FSEditLog.endCurrentLogSegment(FSEditLog.java:1243)
> at
> org.apache.hadoop.hdfs.server.namenode.FSEditLog.rollEditLog(FSEditLog.java:1172)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImage.rollEditLog(FSImage.java:1243)
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.rollEditLog(FSNamesystem.java:6437)
> at
> org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.rollEditLog(NameNodeRpcServer.java:1002)
> at
> org.apache.hadoop.hdfs.protocolPB.NamenodeProtocolServerSideTranslatorPB.rollEditLog(NamenodeProtocolServerSideTranslatorPB.java:142)
> at
> org.apache.hadoop.hdfs.protocol.proto.NamenodeProtocolProtos$NamenodeProtocolService$2.callBlockingMethod(NamenodeProtocolProtos.java:12025)
> at
> org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:617)
> at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:1060)
> at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2086)
> at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2082)
> at java.security.AccessController.doPrivileged(Native Method)
> at javax.security.auth.Subject.doAs(Subject.java:422)
> at
> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1671)
> at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2080)
> 2016-09-23 21:40:59,618 WARN
> org.apache.hadoop.hdfs.qjournal.client.QuorumJournalManager: Aborting
> QuorumOutputStream starting at txid 10562075963
> {code}
> The exception is from EditsDoubleBuffer
> {code}
> public void close() throws IOException {
> Preconditions.checkNotNull(bufCurrent);
> Preconditions.checkNotNull(bufReady);
> int bufSize = bufCurrent.size();
> if (bufSize != 0) {
> throw new IOException("FSEditStream has " + bufSize
> + " bytes still to be flushed and cannot be closed.");
> }
> IOUtils.cleanup(null, bufCurrent, bufReady);
> bufCurrent = bufReady = null;
> }
> {code}
> We can see that FSNamesystem.rollEditLog expects
> EditsDoubleBuffer.bufCurrent to be empty.
> Edits are recorded via FSEditLog$logSync, which does:
> {code}
> * The data is double-buffered within each edit log implementation so that
> * in-memory writing can occur in parallel with the on-disk writing.
> *
> * Each sync occurs in three steps:
> * 1. synchronized, it swaps the double buffer and sets the isSyncRunning
> * flag.
> * 2. unsynchronized, it flushes the data to storage
> * 3. synchronized, it resets the flag and notifies anyone waiting on the
> * sync.
> *
> * The lack of synchronization on step 2 allows other threads to continue
> * to write into the memory buffer while the sync is in progress.
> * Because this step is unsynchronized, actions that need to avoid
> * concurrency with sync() should be synchronized and also call
> * waitForSyncToFinish() before assuming they are running alone.
> */
> {code}
> We can see that step 2 is on-purposely not synchronized to let other threads
> to write into the memory buffer, presumbaly EditsDoubleBuffer.bufCurrent.
> This means that the EditsDoubleBuffer.bufCurrent can be non-empty when
> logSync is done.
> Now if rollEditLog happens, the above exception happens.
> Another interesting observation is, the size of the EditsDoubleBuffer can be
> as large as "private int outputBufferCapacity = 512 * 1024;", which means a
> lot of edits could get buffered before they are flushed to JNs.
> How can rollEdit operation expect the EditsDoubleBuffer.bufCurrent to be
> empty? Or ask in another way, ollEdit operation want to close the stream
> {code}
> org.apache.hadoop.hdfs.server.namenode.JournalSet$JournalAndStream.closeStream(JournalSet.java:115)
> {code}
> where the close operation expects EditsDoubleBuffer.bufCurrent to be empty.
> It seems rollEdit should make sure the EditsDoubleBuffer is flushed in a
> synchronized way before it tries to close the stream. Why it doesn't do that?
> If my above theory is correct, wonder why this issue doesn't show up so often.
--
This message was sent by Atlassian Jira
(v8.3.2#803003)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
