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https://issues.apache.org/jira/browse/HDFS-16538?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

Takanobu Asanuma resolved HDFS-16538.
-------------------------------------
    Fix Version/s: 3.4.0
                   3.2.4
                   3.3.4
         Assignee: qinyuren
       Resolution: Fixed

>  EC decoding failed due to not enough valid inputs
> --------------------------------------------------
>
>                 Key: HDFS-16538
>                 URL: https://issues.apache.org/jira/browse/HDFS-16538
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: erasure-coding
>            Reporter: qinyuren
>            Assignee: qinyuren
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 3.4.0, 3.2.4, 3.3.4
>
>          Time Spent: 1h 10m
>  Remaining Estimate: 0h
>
> Currently, we found this error if the #StripeReader.readStripe() have more 
> than one block read failed.
> We use the EC policy ec(6+3) in our cluster.
> {code:java}
> Caused by: org.apache.hadoop.HadoopIllegalArgumentException: No enough valid 
> inputs are provided, not recoverable
>         at 
> org.apache.hadoop.io.erasurecode.rawcoder.ByteBufferDecodingState.checkInputBuffers(ByteBufferDecodingState.java:119)
>         at 
> org.apache.hadoop.io.erasurecode.rawcoder.ByteBufferDecodingState.<init>(ByteBufferDecodingState.java:47)
>         at 
> org.apache.hadoop.io.erasurecode.rawcoder.RawErasureDecoder.decode(RawErasureDecoder.java:86)
>         at 
> org.apache.hadoop.io.erasurecode.rawcoder.RawErasureDecoder.decode(RawErasureDecoder.java:170)
>         at 
> org.apache.hadoop.hdfs.StripeReader.decodeAndFillBuffer(StripeReader.java:462)
>         at 
> org.apache.hadoop.hdfs.StatefulStripeReader.decode(StatefulStripeReader.java:94)
>         at 
> org.apache.hadoop.hdfs.StripeReader.readStripe(StripeReader.java:406)
>         at 
> org.apache.hadoop.hdfs.DFSStripedInputStream.readOneStripe(DFSStripedInputStream.java:327)
>         at 
> org.apache.hadoop.hdfs.DFSStripedInputStream.readWithStrategy(DFSStripedInputStream.java:420)
>         at org.apache.hadoop.hdfs.DFSInputStream.read(DFSInputStream.java:892)
>         at java.base/java.io.DataInputStream.read(DataInputStream.java:149)
>         at java.base/java.io.DataInputStream.read(DataInputStream.java:149) 
> {code}
>  
> {code:java}
> while (!futures.isEmpty()) {
>   try {
>     StripingChunkReadResult r = StripedBlockUtil
>         .getNextCompletedStripedRead(service, futures, 0);
>     dfsStripedInputStream.updateReadStats(r.getReadStats());
>     DFSClient.LOG.debug("Read task returned: {}, for stripe {}",
>         r, alignedStripe);
>     StripingChunk returnedChunk = alignedStripe.chunks[r.index];
>     Preconditions.checkNotNull(returnedChunk);
>     Preconditions.checkState(returnedChunk.state == StripingChunk.PENDING);
>     if (r.state == StripingChunkReadResult.SUCCESSFUL) {
>       returnedChunk.state = StripingChunk.FETCHED;
>       alignedStripe.fetchedChunksNum++;
>       updateState4SuccessRead(r);
>       if (alignedStripe.fetchedChunksNum == dataBlkNum) {
>         clearFutures();
>         break;
>       }
>     } else {
>       returnedChunk.state = StripingChunk.MISSING;
>       // close the corresponding reader
>       dfsStripedInputStream.closeReader(readerInfos[r.index]);
>       final int missing = alignedStripe.missingChunksNum;
>       alignedStripe.missingChunksNum++;
>       checkMissingBlocks();
>       readDataForDecoding();
>       readParityChunks(alignedStripe.missingChunksNum - missing);
>     } {code}
> This error can be trigger by #StatefulStripeReader.decode.
> The reason is that:
>  # If there are more than one *data block* read failed, the 
> #readDataForDecoding will be called multiple times;
>  # The *decodeInputs array* will be initialized repeatedly.
>  # The *parity* *data* in *decodeInputs array* which filled by 
> #readParityChunks previously will be set to null.
>  
>  
>  



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