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https://issues.apache.org/jira/browse/HDFS-15240?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17194932#comment-17194932
 ] 

Hadoop QA commented on HDFS-15240:
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| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:blue}0{color} | {color:blue} reexec {color} | {color:blue}  1m  
9s{color} | {color:blue} Docker mode activated. {color} |
|| || || || {color:brown} Prechecks {color} ||
| {color:green}+1{color} | {color:green} dupname {color} | {color:green}  0m  
0s{color} | {color:green} No case conflicting files found. {color} |
| {color:green}+1{color} | {color:green} @author {color} | {color:green}  0m  
0s{color} | {color:green} The patch does not contain any @author tags. {color} |
| {color:green}+1{color} | {color:green} test4tests {color} | {color:green}  0m 
 0s{color} | {color:green} The patch appears to include 1 new or modified test 
files. {color} |
|| || || || {color:brown} trunk Compile Tests {color} ||
| {color:blue}0{color} | {color:blue} mvndep {color} | {color:blue}  1m  
4s{color} | {color:blue} Maven dependency ordering for branch {color} |
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green} 23m 
28s{color} | {color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green} 25m 
29s{color} | {color:green} trunk passed with JDK 
Ubuntu-11.0.8+10-post-Ubuntu-0ubuntu118.04.1 {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green} 19m 
47s{color} | {color:green} trunk passed with JDK Private 
Build-1.8.0_265-8u265-b01-0ubuntu2~18.04-b01 {color} |
| {color:green}+1{color} | {color:green} checkstyle {color} | {color:green}  2m 
47s{color} | {color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} mvnsite {color} | {color:green}  3m 
47s{color} | {color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} shadedclient {color} | {color:green} 
22m 19s{color} | {color:green} branch has no errors when building and testing 
our client artifacts. {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  2m 
11s{color} | {color:green} trunk passed with JDK 
Ubuntu-11.0.8+10-post-Ubuntu-0ubuntu118.04.1 {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  3m 
35s{color} | {color:green} trunk passed with JDK Private 
Build-1.8.0_265-8u265-b01-0ubuntu2~18.04-b01 {color} |
| {color:blue}0{color} | {color:blue} spotbugs {color} | {color:blue}  3m 
15s{color} | {color:blue} Used deprecated FindBugs config; considering 
switching to SpotBugs. {color} |
| {color:green}+1{color} | {color:green} findbugs {color} | {color:green}  7m 
57s{color} | {color:green} trunk passed {color} |
|| || || || {color:brown} Patch Compile Tests {color} ||
| {color:blue}0{color} | {color:blue} mvndep {color} | {color:blue}  0m 
23s{color} | {color:blue} Maven dependency ordering for patch {color} |
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green}  2m 
45s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green} 20m 
15s{color} | {color:green} the patch passed with JDK 
Ubuntu-11.0.8+10-post-Ubuntu-0ubuntu118.04.1 {color} |
| {color:green}+1{color} | {color:green} javac {color} | {color:green} 20m 
15s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green} 17m 
35s{color} | {color:green} the patch passed with JDK Private 
Build-1.8.0_265-8u265-b01-0ubuntu2~18.04-b01 {color} |
| {color:green}+1{color} | {color:green} javac {color} | {color:green} 17m 
35s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} checkstyle {color} | {color:green}  2m 
46s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} mvnsite {color} | {color:green}  3m 
43s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} whitespace {color} | {color:green}  0m 
 0s{color} | {color:green} The patch has no whitespace issues. {color} |
| {color:green}+1{color} | {color:green} shadedclient {color} | {color:green} 
15m 27s{color} | {color:green} patch has no errors when building and testing 
our client artifacts. {color} |
| {color:red}-1{color} | {color:red} javadoc {color} | {color:red}  0m 
58s{color} | {color:red} 
hadoop-hdfs-project_hadoop-hdfs-jdkUbuntu-11.0.8+10-post-Ubuntu-0ubuntu118.04.1 
with JDK Ubuntu-11.0.8+10-post-Ubuntu-0ubuntu118.04.1 generated 3 new + 2 
unchanged - 0 fixed = 5 total (was 2) {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  3m 
35s{color} | {color:green} the patch passed with JDK Private 
Build-1.8.0_265-8u265-b01-0ubuntu2~18.04-b01 {color} |
| {color:green}+1{color} | {color:green} findbugs {color} | {color:green}  8m 
27s{color} | {color:green} the patch passed {color} |
|| || || || {color:brown} Other Tests {color} ||
| {color:green}+1{color} | {color:green} unit {color} | {color:green}  9m 
28s{color} | {color:green} hadoop-common in the patch passed. {color} |
| {color:green}+1{color} | {color:green} unit {color} | {color:green}  2m 
10s{color} | {color:green} hadoop-hdfs-client in the patch passed. {color} |
| {color:red}-1{color} | {color:red} unit {color} | {color:red}118m 26s{color} 
| {color:red} hadoop-hdfs in the patch passed. {color} |
| {color:green}+1{color} | {color:green} asflicense {color} | {color:green}  1m 
 3s{color} | {color:green} The patch does not generate ASF License warnings. 
{color} |
| {color:black}{color} | {color:black} {color} | {color:black}318m 53s{color} | 
{color:black} {color} |
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|| Reason || Tests ||
| Failed junit tests | hadoop.hdfs.TestFileChecksum |
|   | hadoop.hdfs.server.blockmanagement.TestBlockTokenWithDFSStriped |
|   | hadoop.hdfs.server.namenode.TestNameNodeRetryCacheMetrics |
|   | hadoop.hdfs.server.namenode.TestAddOverReplicatedStripedBlocks |
|   | hadoop.hdfs.TestGetFileChecksum |
|   | hadoop.hdfs.TestFileChecksumCompositeCrc |
|   | hadoop.hdfs.server.sps.TestExternalStoragePolicySatisfier |
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|| Subsystem || Report/Notes ||
| Docker | ClientAPI=1.40 ServerAPI=1.40 base: 
https://ci-hadoop.apache.org/job/PreCommit-HDFS-Build/152/artifact/out/Dockerfile
 |
| JIRA Issue | HDFS-15240 |
| JIRA Patch URL | 
https://issues.apache.org/jira/secure/attachment/13011452/HDFS-15240.006.patch |
| Optional Tests | dupname asflicense compile javac javadoc mvninstall mvnsite 
unit shadedclient findbugs checkstyle |
| uname | Linux fc9b68c96e9f 4.15.0-112-generic #113-Ubuntu SMP Thu Jul 9 
23:41:39 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux |
| Build tool | maven |
| Personality | personality/hadoop.sh |
| git revision | trunk / d2779de3f52 |
| Default Java | Private Build-1.8.0_265-8u265-b01-0ubuntu2~18.04-b01 |
| Multi-JDK versions | 
/usr/lib/jvm/java-11-openjdk-amd64:Ubuntu-11.0.8+10-post-Ubuntu-0ubuntu118.04.1 
/usr/lib/jvm/java-8-openjdk-amd64:Private 
Build-1.8.0_265-8u265-b01-0ubuntu2~18.04-b01 |
| javadoc | 
https://ci-hadoop.apache.org/job/PreCommit-HDFS-Build/152/artifact/out/diff-javadoc-javadoc-hadoop-hdfs-project_hadoop-hdfs-jdkUbuntu-11.0.8+10-post-Ubuntu-0ubuntu118.04.1.txt
 |
| unit | 
https://ci-hadoop.apache.org/job/PreCommit-HDFS-Build/152/artifact/out/patch-unit-hadoop-hdfs-project_hadoop-hdfs.txt
 |
|  Test Results | 
https://ci-hadoop.apache.org/job/PreCommit-HDFS-Build/152/testReport/ |
| Max. process+thread count | 2630 (vs. ulimit of 5500) |
| modules | C: hadoop-common-project/hadoop-common 
hadoop-hdfs-project/hadoop-hdfs-client hadoop-hdfs-project/hadoop-hdfs U: . |
| Console output | 
https://ci-hadoop.apache.org/job/PreCommit-HDFS-Build/152/console |
| versions | git=2.17.1 maven=3.6.0 findbugs=4.0.6 |
| Powered by | Apache Yetus 0.13.0-SNAPSHOT https://yetus.apache.org |


This message was automatically generated.



> Erasure Coding: dirty buffer causes reconstruction block error
> --------------------------------------------------------------
>
>                 Key: HDFS-15240
>                 URL: https://issues.apache.org/jira/browse/HDFS-15240
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode, erasure-coding
>            Reporter: HuangTao
>            Assignee: HuangTao
>            Priority: Major
>             Fix For: 3.4.0
>
>         Attachments: HDFS-15240.001.patch, HDFS-15240.002.patch, 
> HDFS-15240.003.patch, HDFS-15240.004.patch, HDFS-15240.005.patch, 
> HDFS-15240.006.patch, image-2020-07-16-15-56-38-608.png
>
>
> When read some lzo files we found some blocks were broken.
> I read back all internal blocks(b0-b8) of the block group(RS-6-3-1024k) from 
> DN directly, and choose 6(b0-b5) blocks to decode other 3(b6', b7', b8') 
> blocks. And find the longest common sequenece(LCS) between b6'(decoded) and 
> b6(read from DN)(b7'/b7 and b8'/b8).
> After selecting 6 blocks of the block group in combinations one time and 
> iterating through all cases, I find one case that the length of LCS is the 
> block length - 64KB, 64KB is just the length of ByteBuffer used by 
> StripedBlockReader. So the corrupt reconstruction block is made by a dirty 
> buffer.
> The following log snippet(only show 2 of 28 cases) is my check program 
> output. In my case, I known the 3th block is corrupt, so need other 5 blocks 
> to decode another 3 blocks, then find the 1th block's LCS substring is block 
> length - 64kb.
> It means (0,1,2,4,5,6)th blocks were used to reconstruct 3th block, and the 
> dirty buffer was used before read the 1th block.
> Must be noted that StripedBlockReader read from the offset 0 of the 1th block 
> after used the dirty buffer.
> EDITED for readability.
> {code:java}
> decode from block[0, 2, 3, 4, 5, 7] to generate block[1', 6', 8']
> Check the first 131072 bytes between block[1] and block[1'], the longest 
> common substring length is 4
> Check the first 131072 bytes between block[6] and block[6'], the longest 
> common substring length is 4
> Check the first 131072 bytes between block[8] and block[8'], the longest 
> common substring length is 4
> decode from block[0, 2, 3, 4, 5, 6] to generate block[1', 7', 8']
> Check the first 131072 bytes between block[1] and block[1'], the longest 
> common substring length is 65536
> CHECK AGAIN: all 27262976 bytes between block[1] and block[1'], the longest 
> common substring length is 27197440  # this one
> Check the first 131072 bytes between block[7] and block[7'], the longest 
> common substring length is 4
> Check the first 131072 bytes between block[8] and block[8'], the longest 
> common substring length is 4{code}
> Now I know the dirty buffer causes reconstruction block error, but how does 
> the dirty buffer come about?
> After digging into the code and DN log, I found this following DN log is the 
> root reason.
> {code:java}
> [INFO] [stripedRead-1017] : Interrupted while waiting for IO on channel 
> java.nio.channels.SocketChannel[connected local=/xxxxxxxx:52586 
> remote=/xxxxxxxx:50010]. 180000 millis timeout left.
> [WARN] [StripedBlockReconstruction-199] : Failed to reconstruct striped 
> block: BP-714356632-xxxxxxxx-1519726836856:blk_-YYYYYYYYYYYYYY_3472979393
> java.lang.NullPointerException
>     at 
> org.apache.hadoop.hdfs.util.StripedBlockUtil.getNextCompletedStripedRead(StripedBlockUtil.java:314)
>     at 
> org.apache.hadoop.hdfs.server.datanode.erasurecode.StripedReader.doReadMinimumSources(StripedReader.java:308)
>     at 
> org.apache.hadoop.hdfs.server.datanode.erasurecode.StripedReader.readMinimumSources(StripedReader.java:269)
>     at 
> org.apache.hadoop.hdfs.server.datanode.erasurecode.StripedBlockReconstructor.reconstruct(StripedBlockReconstructor.java:94)
>     at 
> org.apache.hadoop.hdfs.server.datanode.erasurecode.StripedBlockReconstructor.run(StripedBlockReconstructor.java:60)
>     at 
> java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
>     at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
>     at 
> java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
>     at 
> java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
>     at java.base/java.lang.Thread.run(Thread.java:834) {code}
> Reading from DN may timeout(hold by a future(F)) and output the INFO log, but 
> the futures that contains the future(F)  is cleared, 
> {code:java}
> return new StripingChunkReadResult(futures.remove(future),
>     StripingChunkReadResult.CANCELLED); {code}
> futures.remove(future) cause NPE. So the EC reconstruction is failed. In the 
> finally phase, the code snippet in *getStripedReader().close()* 
> {code:java}
> reconstructor.freeBuffer(reader.getReadBuffer());
> reader.freeReadBuffer();
> reader.closeBlockReader(); {code}
> free buffer firstly, but the StripedBlockReader still holds the buffer and 
> write it, that pollute the buffer of BufferPool.



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