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https://issues.apache.org/jira/browse/HDFS-10490?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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He Tianyi updated HDFS-10490:
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Status: Patch Available (was: Open)
> Client may never recovery replica after a timeout during sending packet
> -----------------------------------------------------------------------
>
> Key: HDFS-10490
> URL: https://issues.apache.org/jira/browse/HDFS-10490
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Affects Versions: 2.6.0
> Reporter: He Tianyi
> Attachments: HDFS-10490.patch
>
>
> For newly created replica, a meta file is created in constructor of
> {{BlockReceiver}} (for {{WRITE_BLOCK}} op). Its header will be written lazily
> (buffered in memory first by {{BufferedOutputStream}}).
> If following packets fail to deliver (e.g. in extreme network condition),
> the header may never get flush until closed.
> However, {{BlockReceiver}} will not call close until block receiving is
> finished or exception(s) encountered. Also in extreme network condition, both
> RST & FIN may not deliver in time.
> In this case, if client tries to initiates a {{transferBlock}} to a new
> datanode (in {{addDatanode2ExistingPipeline}}), existing datanode will see an
> empty meta if its {{BlockReceiver}} did not close in time.
> Then, after HDFS-3429, a default {{DataChecksum}} (NULL, 512) will be used
> during transfer. So when client then tries to recover pipeline after
> completely transferred, it may encounter the following exception:
> {noformat}
> java.io.IOException: Client requested checksum DataChecksum(type=CRC32C,
> chunkSize=4096) when appending to an existing block with different chunk
> size: DataChecksum(type=NULL, chunkSize=512)
> at
> org.apache.hadoop.hdfs.server.datanode.ReplicaInPipeline.createStreams(ReplicaInPipeline.java:230)
> at
> org.apache.hadoop.hdfs.server.datanode.BlockReceiver.<init>(BlockReceiver.java:226)
> at
> org.apache.hadoop.hdfs.server.datanode.DataXceiver.writeBlock(DataXceiver.java:798)
> at
> org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.opWriteBlock(Receiver.java:166)
> at
> org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.processOp(Receiver.java:76)
> at
> org.apache.hadoop.hdfs.server.datanode.DataXceiver.run(DataXceiver.java:243)
> at java.lang.Thread.run(Thread.java:745)
> {noformat}
> This will repeat, until exhausted by datanode replacement policy.
> Also to note that, with bad luck (like I), 20k clients are all doing this.
> It's to some extend a DDoS attack to NameNode (because of
> getAdditionalDataNode calls).
> I suggest we flush immediately after header is written, preventing anybody
> from seeing empty meta file for avoiding the issue.
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