apache/hadoop · error · IOException

processCacheReport from dead or unregistered datanode: datan

Error message

processCacheReport from dead or unregistered datanode: datanode

What it means

Error "processCacheReport from dead or unregistered datanode: datanode" thrown in apache/hadoop.

Source

Thrown at hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/CacheManager.java:1019

      }
    }
  }

  public final void processCacheReport(final DatanodeID datanodeID,
      final List<Long> blockIds) throws IOException {
    if (!enabled) {
      LOG.debug("Ignoring cache report from {} because {} = false. number of blocks: {}",
          datanodeID, DFS_NAMENODE_CACHING_ENABLED_KEY, blockIds.size());
      return;
    }
    namesystem.writeLock(RwLockMode.BM);
    final long startTime = Time.monotonicNow();
    final long endTime;
    try {
      final DatanodeDescriptor datanode = 
          blockManager.getDatanodeManager().getDatanode(datanodeID);
      if (datanode == null || !datanode.isRegistered()) {
        throw new IOException(
            "processCacheReport from dead or unregistered datanode: " +
            datanode);
      }
      processCacheReportImpl(datanode, blockIds);
    } finally {
      endTime = Time.monotonicNow();
      namesystem.writeUnlock(RwLockMode.BM, "processCacheReport");
    }

    // Log the block report processing stats from Namenode perspective
    final NameNodeMetrics metrics = NameNode.getNameNodeMetrics();
    if (metrics != null) {
      metrics.addCacheBlockReport((int) (endTime - startTime));
    }
    LOG.debug("Processed cache report from {}, blocks: {}, processing time: {} msecs",
        datanodeID, blockIds.size(), (endTime - startTime));
  }

View on GitHub (pinned to 2add963021)

Solutions

1. Check why the DataNode is marked dead or unregistered (network partition, crash) and bring it back into the cluster.
2. Usually benign during DataNode restarts; ensure the DataNode re-registers with the NameNode.

When it happens

Trigger: Cache report received from a DataNode that is dead or not registered with the NameNode.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/b5da551a9bf3a76a. Report an issue: GitHub.