apache/hadoop · error · UnregisteredNodeException

Unregistered server: {}

Error message

Unregistered server: {}

What it means

Error "Unregistered server: {}" thrown in apache/hadoop.

Source

Thrown at hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNodeRpcServer.java:1785

    namesystem.handleLifeline(nodeReg, report, dnCacheCapacity, dnCacheUsed,
        xceiverCount, xmitsInProgress, failedVolumes, volumeFailureSummary);
  }

  /** 
   * Verifies the given registration.
   * 
   * @param nodeReg node registration
   * @throws UnregisteredNodeException if the registration is invalid
   */
  private void verifyRequest(NodeRegistration nodeReg) throws IOException {
    // verify registration ID
    final String id = nodeReg.getRegistrationID();
    final String expectedID = namesystem.getRegistrationID();
    if (!expectedID.equals(id)) {
      LOG.warn("Registration IDs mismatched: the "
          + nodeReg.getClass().getSimpleName() + " ID is " + id
          + " but the expected ID is " + expectedID);
       throw new UnregisteredNodeException(nodeReg);
    }
  }

  @Override // RefreshAuthorizationPolicyProtocol
  public void refreshServiceAcl() throws IOException {
    checkNNStartup();
    if (!serviceAuthEnabled) {
      throw new AuthorizationException("Service Level Authorization not enabled!");
    }

    this.clientRpcServer.refreshServiceAcl(new Configuration(), new HDFSPolicyProvider());
    if (this.serviceRpcServer != null) {
      this.serviceRpcServer.refreshServiceAcl(new Configuration(), new HDFSPolicyProvider());
    }
    namesystem.logAuditEvent(true, "refreshServiceAcl", null);
  }

  @Override // RefreshAuthorizationPolicyProtocol

View on GitHub (pinned to 2add963021)

Solutions

1. Register the DataNode/service with the NameNode (check clusterID/namespaceID match) before it sends requests.

When it happens

Trigger: A request arrives from a DataNode or service that has not registered with this NameNode.

Common situations: A misconfigured DataNode pointing at the wrong NameNode or cluster, or first-contact before registration.

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/dee49c338f91723f. Report an issue: GitHub.