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From "Kai Zheng (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-11882) Client fails if acknowledged size is greater than bytes sent
Date Thu, 10 Aug 2017 06:08:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11882?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16121110#comment-16121110

Kai Zheng commented on HDFS-11882:

Hi [~ajisakaa],

I'm trying to understand what you meant.
bq. When sentBytes is 18*64k and the cellSize is 64k, 
The used schema should be 6 + 3. It sent 2 full strips of 2 x 9 x 64k bytes.
bq. DN1~8 will have two 64k data blocks, DN9~10 will have one 64k data block, and DN11~14
will have two 64k parity blocks. 
In the schema of 6 + 3, it only needs to write to 9 DNs. But here it looks like to write DN1~14
or 14 DNs, why? I'm pretty confused here.
bq. In this situation, getNumAckedStriples() will return 2 if DN9 and DN10 are failing. 
OK, if it return 2 that means the acked strips number is 2, so the acked bytes should be 2
x 9 x 64k, which should be right equal to the sent bytes.
bq. That way, in the testcase ackedBytes will become 20*64k, which is greater than sentBytes.
Looks like 2 extra cells in addition to the 2 full strips also acked, since DN9 and DN10 are
failing, they shouldn't contribute to the 2 extra acked cells.

I'm also trying to understand the root cause, why the acked bytes are greater than the sent
bytes. Cloud you help explain a little bit for me? Thanks!

> Client fails if acknowledged size is greater than bytes sent
> ------------------------------------------------------------
>                 Key: HDFS-11882
>                 URL: https://issues.apache.org/jira/browse/HDFS-11882
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: erasure-coding, test
>            Reporter: Akira Ajisaka
>            Assignee: Akira Ajisaka
>            Priority: Critical
>              Labels: hdfs-ec-3.0-must-do
>         Attachments: HDFS-11882.01.patch, HDFS-11882.02.patch, HDFS-11882.regressiontest.patch
> Some tests of erasure coding fails by the following exception. The following test was
removed by HDFS-11823, however, this type of error can happen in real cluster.
> {noformat}
> Running org.apache.hadoop.hdfs.TestDFSRSDefault10x4StripedOutputStreamWithFailure
> Tests run: 14, Failures: 0, Errors: 1, Skipped: 10, Time elapsed: 89.086 sec <<<
FAILURE! - in org.apache.hadoop.hdfs.TestDFSRSDefault10x4StripedOutputStreamWithFailure
> testMultipleDatanodeFailure56(org.apache.hadoop.hdfs.TestDFSRSDefault10x4StripedOutputStreamWithFailure)
 Time elapsed: 38.831 sec  <<< ERROR!
> java.lang.IllegalStateException: null
> 	at com.google.common.base.Preconditions.checkState(Preconditions.java:129)
> 	at org.apache.hadoop.hdfs.DFSStripedOutputStream.updatePipeline(DFSStripedOutputStream.java:780)
> 	at org.apache.hadoop.hdfs.DFSStripedOutputStream.checkStreamerFailures(DFSStripedOutputStream.java:664)
> 	at org.apache.hadoop.hdfs.DFSStripedOutputStream.closeImpl(DFSStripedOutputStream.java:1034)
> 	at org.apache.hadoop.hdfs.DFSOutputStream.close(DFSOutputStream.java:842)
> 	at org.apache.hadoop.fs.FSDataOutputStream$PositionCache.close(FSDataOutputStream.java:72)
> 	at org.apache.hadoop.fs.FSDataOutputStream.close(FSDataOutputStream.java:101)
> 	at org.apache.hadoop.hdfs.TestDFSStripedOutputStreamWithFailure.runTest(TestDFSStripedOutputStreamWithFailure.java:472)
> 	at org.apache.hadoop.hdfs.TestDFSStripedOutputStreamWithFailure.runTestWithMultipleFailure(TestDFSStripedOutputStreamWithFailure.java:381)
> 	at org.apache.hadoop.hdfs.TestDFSStripedOutputStreamWithFailure.testMultipleDatanodeFailure56(TestDFSStripedOutputStreamWithFailure.java:245)
> 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> 	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
> 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
> 	at java.lang.reflect.Method.invoke(Method.java:498)
> 	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
> 	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
> 	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
> 	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
> 	at org.junit.internal.runners.statements.FailOnTimeout$StatementThread.run(FailOnTimeout.java:74)
> {noformat}

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