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https://issues.apache.org/jira/browse/HDFS-16115?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17376571#comment-17376571
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Daniel Ma commented on HDFS-16115:
----------------------------------
hello [~hexiaoqiao].
Thanks for review,
1-For non-fatal error, I define two kinds at present:
These two errors are caused by too many threads in OS and too many open files
in OS, which probably can recover soon.
Even if the OS limit cannot be recovered proactively, users expect that the
HDFS can recover automatically after manual access.
{code:java}
//代码占位符
enum NON_FATAL_TYPES {
THREAD_EXCEED("unable to create new native thread"),
FILE_EXCEED("Too many open files");
private final String errorMsg;
NON_FATAL_TYPES(String errorMsg){
this.errorMsg = errorMsg;
}
public String getErrorMsg() {
return errorMsg;
}
}
{code}
2-the main defect of HDFS-15651 is that BPServiceActor thread will never back
to normal unless restart DataNode which is always unacceptable in production
environment reported by real users. That is why I develop this feature.
> Asynchronously handle BPServiceActor command mechanism may result in
> BPServiceActor never fails even CommandProcessingThread is closed with fatal
> error.
> --------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: HDFS-16115
> URL: https://issues.apache.org/jira/browse/HDFS-16115
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: datanode
> Affects Versions: 3.3.1
> Reporter: Daniel Ma
> Priority: Critical
> Fix For: 3.3.1
>
> Attachments: 0001-HDFS-16115.patch
>
>
> It is an improvement issue. Actually the issue has two sub issues:
> 1- BPServerActor thread handle commands from NameNode in aysnchronous way (
> CommandProcessThread handle commands ), so if there are any exceptions or
> errors happen in thread CommandProcessthread resulting the thread fails and
> stop, of which BPServiceActor cannot aware and still keep putting commands
> from namenode into queues waiting to be handled by CommandProcessThread,
> actually CommandProcessThread was dead already.
> 2-the second sub issue is based on the first one, if CommandProcessThread was
> dead owing to some non-fatal errors like "can not create native thread" which
> is caused by too many threads existed in OS, this kind of problem should be
> given much more torlerance instead of simply shudown the thread and never
> recover automatically, because the non-fatal errors mentioned above probably
> can be recovered soon by itself,
> {code:java}
> //代码占位符
> 2021-07-02 16:26:02,315 | WARN | Command processor | Exception happened when
> process queue BPServiceActor.java:1393
> java.lang.OutOfMemoryError: unable to create new native thread
> at java.lang.Thread.start0(Native Method)
> at java.lang.Thread.start(Thread.java:717)
> at
> java.util.concurrent.ThreadPoolExecutor.addWorker(ThreadPoolExecutor.java:957)
> at
> java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1367)
> at
> org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetAsyncDiskService.execute(FsDatasetAsyncDiskService.java:180)
> at
> org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetAsyncDiskService.deleteAsync(FsDatasetAsyncDiskService.java:229)
> at
> org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.invalidate(FsDatasetImpl.java:2315)
> at
> org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.invalidate(FsDatasetImpl.java:2237)
> at
> org.apache.hadoop.hdfs.server.datanode.BPOfferService.processCommandFromActive(BPOfferService.java:752)
> at
> org.apache.hadoop.hdfs.server.datanode.BPOfferService.processCommandFromActor(BPOfferService.java:698)
> at
> org.apache.hadoop.hdfs.server.datanode.BPServiceActor$CommandProcessingThread.processCommand(BPServiceActor.java:1417)
> at
> org.apache.hadoop.hdfs.server.datanode.BPServiceActor$CommandProcessingThread.lambda$enqueue$2(BPServiceActor.java:1463)
> at
> org.apache.hadoop.hdfs.server.datanode.BPServiceActor$CommandProcessingThread.processQueue(BPServiceActor.java:1382)
> at
> org.apache.hadoop.hdfs.server.datanode.BPServiceActor$CommandProcessingThread.run(BPServiceActor.java:1365)
> {code}
> currently, Datanode BPServiceActor cannot turn to normal even when the
> non-fatal error was eliminated.
> Therefore, in this patch, two things will be done:
> 1-Add retry mechanism in BPServiceActor thread and CommandProcessThread
> thread which is 5 by default and configurable;
> 2-Add a monitor periodical thread in BPOfferService, if a BPServiceActor
> thread is dead owing to too many times non-fatal error, it should not be
> simply removed from BPServviceActor lists stored in BPOfferService, instead,
> the monitor thread will periodically try to start these special dead
> BPServiceActor thread. the interval is also configurable.
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