{"record":{"id":"ca176816a937d89d","repo":"apache/hadoop","slug":"cannot-locate-a-registered-namenode-for-from","errorCode":null,"errorMessage":"Cannot locate a registered namenode for {} from {}","messagePattern":"Cannot locate a registered namenode for (.+?) from (.+?)","errorType":"exception","errorClass":"IOException","httpStatus":null,"severity":"error","filePath":"hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterRpcClient.java","lineNumber":1825,"sourceCode":"    CallerContext.setCurrent(originContext);\n  }\n\n  /**\n   * Get a prioritized list of NNs that share the same block pool ID (in the\n   * same namespace). NNs that are reported as ACTIVE will be first in the list.\n   *\n   * @param bpId The blockpool ID for the namespace.\n   * @return A prioritized list of NNs to use for communication.\n   * @throws IOException If a NN cannot be located for the block pool ID.\n   */\n  private List<? extends FederationNamenodeContext> getNamenodesForBlockPoolId(\n      final String bpId) throws IOException {\n\n    List<? extends FederationNamenodeContext> namenodes =\n        namenodeResolver.getNamenodesForBlockPoolId(bpId);\n\n    if (namenodes == null || namenodes.isEmpty()) {\n      throw new IOException(\"Cannot locate a registered namenode for \" + bpId +\n          \" from \" + router.getRouterId());\n    }\n    return namenodes;\n  }\n\n  /**\n   * Get the nameservice identifier for a block pool.\n   *\n   * @param bpId Identifier of the block pool.\n   * @return Nameservice identifier.\n   * @throws IOException If a NN cannot be located for the block pool ID.\n   */\n  private String getNameserviceForBlockPoolId(final String bpId)\n      throws IOException {\n    List<? extends FederationNamenodeContext> namenodes =\n        getNamenodesForBlockPoolId(bpId);\n    FederationNamenodeContext namenode = namenodes.get(0);\n    return namenode.getNameserviceId();","sourceCodeStart":1807,"sourceCodeEnd":1843,"githubUrl":"https://github.com/apache/hadoop/blob/2add9630210752f88ceb1bb74eb65e37bf41da8e/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterRpcClient.java#L1807-L1843","documentation":"Error \"Cannot locate a registered namenode for {} from {}\" thrown in apache/hadoop.","triggerScenarios":"The resolver could not find a registered namenode entry matching the requested id/nameservice.","commonSituations":"Namenode never registered, registration expired, or the Router queried a nameservice with no members.","solutions":["Confirm the namenode has registered in the State Store (dfsrouteradmin -ls).","Check that the namenode's heartbeat/conf registration includes the nameservice id the Router expects.","Restart the namenode's NamenodeHeartbeatService if registration stopped."],"exampleFix":null,"handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"2add9630210752f88ceb1bb74eb65e37bf41da8e","analyzedAt":"2026-08-22T19:55:07.957Z","schemaVersion":2},"datasetVersion":"2026-08-23T01:17:44.959Z"}