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https://issues.apache.org/jira/browse/HDFS-14646?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16919806#comment-16919806
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Chao Sun commented on HDFS-14646:
---------------------------------
Thanks [~xudongcao] for clarification! I think overall the patch looks good. I
have a few comments:
- in {{ImageServlet#PutImageParams}}, we should check if the value for
{{CHECK_SHOULD_PUT}} is null. This will avoid the issue where you have one NN
w/o the patch trying to upload image to a NN w/ the patch. Also it seems the
boxing to {{Boolean}} is unnecessary.
- in {{ImageServlet#doPut}}, could we return before
{{request.getInputStream()}}?
- nit: the comments on {{TransferImage#checkShouldPut}} is not proper Java doc
format.
- nit: in {{TransferImage#setUpConnection}}, we should keep the syntax {{catch
(AuthenticationException | URISyntaxException e)}} as trunk is already on Java
8.
> Standby NameNode should not upload fsimage to an inappropriate NameNode.
> ------------------------------------------------------------------------
>
> Key: HDFS-14646
> URL: https://issues.apache.org/jira/browse/HDFS-14646
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: hdfs
> Affects Versions: 3.1.2
> Reporter: Xudong Cao
> Assignee: Xudong Cao
> Priority: Major
> Attachments: HDFS-14646.000.patch, HDFS-14646.001.patch,
> HDFS-14646.002.patch, HDFS-14646.003.patch
>
>
> *Problem Description:*
> In the multi-NameNode scenario, when a SNN uploads a FsImage, it will put
> the image to all other NNs (whether the peer NN is an ANN or not), and even
> if the peer NN immediately replies an error (such as
> TransferResult.NOT_ACTIVE_NAMENODE_FAILURE, TransferResult
> .OLD_TRANSACTION_ID_FAILURE, etc.), the local SNN will not terminate the put
> process immediately, but will put the FsImage completely to the peer NN, and
> will not read the peer NN's reply until the put is completed.
> Depending on the version of Jetty, this behavior can lead to different
> consequences, I tested it under 2.7.2 and trunk version.
> *1.In Hadoop 2.7.2 (with Jetty 6.1.26)*
> After peer NN called HttpServletResponse.sendError(), the underlying TCP
> connection will still be established, and the data SNN sent will be read by
> Jetty framework itself in the peer NN side, so the SNN will insignificantly
> send the FsImage to the peer NN continuously, causing a waste of time and
> bandwidth. In a relatively large HDFS cluster, the size of FsImage can often
> reach about 30GB, This is indeed a big waste.
> *2.In trunk version (with Jetty 9.3.27)*
> After peer NN called HttpServletResponse.sendError(), the underlying TCP
> connection will be auto closed, and then SNN will directly get an "Error
> writing request body to server" exception, as below, note this test needs a
> relatively big FSImage (e.g. 10MB level):
> {code:java}
> 2019-08-17 03:59:25,413 INFO namenode.TransferFsImage: Sending fileName:
> /tmp/hadoop-root/dfs/name/current/fsimage_0000000000003364240, fileSize:
> 9864721. Sent total: 524288 bytes. Size of last segment intended to send:
> 4096 bytes.
> java.io.IOException: Error writing request body to server
> at
> sun.net.www.protocol.http.HttpURLConnection$StreamingOutputStream.checkError(HttpURLConnection.java:3587)
> at
> sun.net.www.protocol.http.HttpURLConnection$StreamingOutputStream.write(HttpURLConnection.java:3570)
> at
> org.apache.hadoop.hdfs.server.namenode.TransferFsImage.copyFileToStream(TransferFsImage.java:396)
> at
> org.apache.hadoop.hdfs.server.namenode.TransferFsImage.writeFileToPutRequest(TransferFsImage.java:340)
> at
> org.apache.hadoop.hdfs.server.namenode.TransferFsImage.uploadImage(TransferFsImage.java:314)
> at
> org.apache.hadoop.hdfs.server.namenode.TransferFsImage.uploadImageFromStorage(TransferFsImage.java:249)
> at
> org.apache.hadoop.hdfs.server.namenode.ha.StandbyCheckpointer$1.call(StandbyCheckpointer.java:277)
> at
> org.apache.hadoop.hdfs.server.namenode.ha.StandbyCheckpointer$1.call(StandbyCheckpointer.java:272)
> at java.util.concurrent.FutureTask.run(FutureTask.java:266)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
> at java.lang.Thread.run(Thread.java:748)
> 2019-08-17 03:59:25,422 INFO namenode.TransferFsImage: Sending fileName:
> /tmp/hadoop-root/dfs/name/current/fsimage_0000000000003364240, fileSize:
> 9864721. Sent total: 851968 bytes. Size of last segment intended to send:
> 4096 bytes.
> java.io.IOException: Error writing request body to server
> at
> sun.net.www.protocol.http.HttpURLConnection$StreamingOutputStream.checkError(HttpURLConnection.java:3587)
> at
> sun.net.www.protocol.http.HttpURLConnection$StreamingOutputStream.write(HttpURLConnection.java:3570)
> at
> org.apache.hadoop.hdfs.server.namenode.TransferFsImage.copyFileToStream(TransferFsImage.java:396)
> at
> org.apache.hadoop.hdfs.server.namenode.TransferFsImage.writeFileToPutRequest(TransferFsImage.java:340)
> {code}
>
> *Solution:*
> A standby NameNode should not upload fsimage to an inappropriate NameNode,
> when he plans to put a FsImage to the peer NN, he need to check whether he
> really need to put it at this time.
> In detail, local SNN should establish an HTTP connection with the peer NN,
> send the put request, and then immediately read the response (this is the key
> point). If the peer NN does not reply an HTTP_OK, it means the local SNN
> should not put image at this time.
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