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  1. Hadoop HDFS
  2. HDFS-15963

Unreleased volume references cause an infinite loop

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    • Hadoop Flags:
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      Description

      When BlockSender throws an exception because the meta-data cannot be found, the volume reference obtained by the thread is not released, which causes the thread trying to remove the volume to wait and fall into an infinite loop.

      boolean checkVolumesRemoved() {
        Iterator<FsVolumeImpl> it = volumesBeingRemoved.iterator();
        while (it.hasNext()) {
          FsVolumeImpl volume = it.next();
          if (!volume.checkClosed()) {
            return false;
          }
          it.remove();
        }
        return true;
      }
      
      boolean checkClosed() {
        // always be true.
        if (this.reference.getReferenceCount() > 0) {
          FsDatasetImpl.LOG.debug("The reference count for {} is {}, wait to be 0.",
              this, reference.getReferenceCount());
          return false;
        }
        return true;
      }
      

      At the same time, because the thread has been holding checkDirsLock when removing the volume, other threads trying to acquire the same lock will be permanently blocked.
      Similar problems also occur in RamDiskAsyncLazyPersistService and FsDatasetAsyncDiskService.
      This patch releases the three previously unreleased volume references.

        Attachments

        1. HDFS-15963.003.patch
          16 kB
          Shuyan Zhang
        2. HDFS-15963.002.patch
          17 kB
          Shuyan Zhang
        3. HDFS-15963.001.patch
          18 kB
          Shuyan Zhang

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              • Assignee:
                zhangshuyan Shuyan Zhang
                Reporter:
                zhangshuyan Shuyan Zhang
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