apache/hadoop · error · IOException

Could not obtain block {}

Error message

Could not obtain block {}

What it means

Error "Could not obtain block {}" thrown in apache/hadoop.

Source

Thrown at hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NamenodeFsck.java:1082

   * around.
   */
  private void copyBlock(final DFSClient dfs, LocatedBlock lblock,
      OutputStream fos) throws Exception {
    int failures = 0;
    InetSocketAddress targetAddr = null;
    Set<DatanodeInfo> deadNodes = new HashSet<DatanodeInfo>();
    BlockReader blockReader = null;
    ExtendedBlock block = lblock.getBlock();

    while (blockReader == null) {
      DatanodeInfo chosenNode;

      try {
        chosenNode = bestNode(dfs, lblock.getLocations(), deadNodes);
        targetAddr = NetUtils.createSocketAddr(chosenNode.getXferAddr());
      }  catch (IOException ie) {
        if (failures >= HdfsClientConfigKeys.DFS_CLIENT_MAX_BLOCK_ACQUIRE_FAILURES_DEFAULT) {
          throw new IOException("Could not obtain block " + lblock, ie);
        }
        LOG.info("Could not obtain block from any node:  " + ie);
        try {
          Thread.sleep(10000);
        }  catch (InterruptedException iex) {
        }
        deadNodes.clear();
        failures++;
        continue;
      }
      try {
        String file = BlockReaderFactory.getFileName(targetAddr,
            block.getBlockPoolId(), block.getBlockId());
        blockReader = new BlockReaderFactory(dfs.getConf()).
            setFileName(file).
            setBlock(block).
            setBlockToken(lblock.getBlockToken()).
            setStartOffset(0).

View on GitHub (pinned to 2add963021)

Solutions

1. Retry the fsck; if persistent, check DataNode availability and network connectivity for the block's replicas.

When it happens

Trigger: fsck fails to fetch a block's contents from any DataNode holding a replica.

Common situations: Corrupted or unreachable DataNodes while fsck verifies block data.

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/279354112b2b4440. Report an issue: GitHub.