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https://issues.apache.org/jira/browse/HDFS-15413?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17232751#comment-17232751
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gaozhan ding commented on HDFS-15413:
-------------------------------------
[~ferhui] Do you have any suggestions on this issue? We are facing the same
problem.
> DFSStripedInputStream throws exception when datanodes close idle connections
> ----------------------------------------------------------------------------
>
> Key: HDFS-15413
> URL: https://issues.apache.org/jira/browse/HDFS-15413
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: ec, erasure-coding, hdfs-client
> Affects Versions: 3.1.3
> Environment: - Hadoop 3.1.3
> - erasure coding with ISA-L and RS-3-2-1024k scheme
> - running in kubernetes
> - dfs.client.socket-timeout = 10000
> - dfs.datanode.socket.write.timeout = 10000
> Reporter: Andrey Elenskiy
> Priority: Critical
> Attachments: out.log
>
>
> We've run into an issue with compactions failing in HBase when erasure coding
> is enabled on a table directory. After digging further I was able to narrow
> it down to a seek + read logic and able to reproduce the issue with hdfs
> client only:
> {code:java}
> import org.apache.hadoop.conf.Configuration;
> import org.apache.hadoop.fs.Path;
> import org.apache.hadoop.fs.FileSystem;
> import org.apache.hadoop.fs.FSDataInputStream;
> public class ReaderRaw {
> public static void main(final String[] args) throws Exception {
> Path p = new Path(args[0]);
> int bufLen = Integer.parseInt(args[1]);
> int sleepDuration = Integer.parseInt(args[2]);
> int countBeforeSleep = Integer.parseInt(args[3]);
> int countAfterSleep = Integer.parseInt(args[4]);
> Configuration conf = new Configuration();
> FSDataInputStream istream = FileSystem.get(conf).open(p);
> byte[] buf = new byte[bufLen];
> int readTotal = 0;
> int count = 0;
> try {
> while (true) {
> istream.seek(readTotal);
> int bytesRemaining = bufLen;
> int bufOffset = 0;
> while (bytesRemaining > 0) {
> int nread = istream.read(buf, 0, bufLen);
> if (nread < 0) {
> throw new Exception("nread is less than zero");
> }
> readTotal += nread;
> bufOffset += nread;
> bytesRemaining -= nread;
> }
> count++;
> if (count == countBeforeSleep) {
> System.out.println("sleeping for " + sleepDuration + "
> milliseconds");
> Thread.sleep(sleepDuration);
> System.out.println("resuming");
> }
> if (count == countBeforeSleep + countAfterSleep) {
> System.out.println("done");
> break;
> }
> }
> } catch (Exception e) {
> System.out.println("exception on read " + count + " read total "
> + readTotal);
> throw e;
> }
> }
> }
> {code}
> The issue appears to be due to the fact that datanodes close the connection
> of EC client if it doesn't fetch next packet for longer than
> dfs.client.socket-timeout. The EC client doesn't retry and instead assumes
> that those datanodes went away resulting in "missing blocks" exception.
> I was able to consistently reproduce with the following arguments:
> {noformat}
> bufLen = 1000000 (just below 1MB which is the size of the stripe)
> sleepDuration = (dfs.client.socket-timeout + 1) * 1000 (in our case 11000)
> countBeforeSleep = 1
> countAfterSleep = 7
> {noformat}
> I've attached the entire log output of running the snippet above against
> erasure coded file with RS-3-2-1024k policy. And here are the logs from
> datanodes of disconnecting the client:
> datanode 1:
> {noformat}
> 2020-06-15 19:06:20,697 INFO datanode.DataNode: Likely the client has stopped
> reading, disconnecting it (datanode-v11-0-hadoop.hadoop:9866:DataXceiver
> error processing READ_BLOCK operation src: /10.128.23.40:53748 dst:
> /10.128.14.46:9866); java.net.SocketTimeoutException: 10000 millis timeout
> while waiting for channel to be ready for write. ch :
> java.nio.channels.SocketChannel[connected local=/10.128.14.46:9866
> remote=/10.128.23.40:53748]
> {noformat}
> datanode 2:
> {noformat}
> 2020-06-15 19:06:20,341 INFO datanode.DataNode: Likely the client has stopped
> reading, disconnecting it (datanode-v11-1-hadoop.hadoop:9866:DataXceiver
> error processing READ_BLOCK operation src: /10.128.23.40:48772 dst:
> /10.128.9.42:9866); java.net.SocketTimeoutException: 10000 millis timeout
> while waiting for channel to be ready for write. ch :
> java.nio.channels.SocketChannel[connected local=/10.128.9.42:9866
> remote=/10.128.23.40:48772]
> {noformat}
> datanode 3:
> {noformat}
> 2020-06-15 19:06:20,467 INFO datanode.DataNode: Likely the client has stopped
> reading, disconnecting it (datanode-v11-3-hadoop.hadoop:9866:DataXceiver
> error processing READ_BLOCK operation src: /10.128.23.40:57184 dst:
> /10.128.16.13:9866); java.net.SocketTimeoutException: 10000 millis timeout
> while waiting for channel to be ready for write. ch :
> java.nio.channels.SocketChannel[connected local=/10.128.16.13:9866
> remote=/10.128.23.40:57184]
> {noformat}
> I've tried running the same code again non-ec files with replication of 3 and
> was not able to reproduce the issue with any parameters. Looking through the
> code, it's pretty clear that non-ec DFSInputStream retries reads after
> exception:
> https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSInputStream.java#L844
> Let me know if you need any more information that can help you out with
> addressing this issue.
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