{"record":{"id":"d6d560b92d89cf39","repo":"apache/hadoop","slug":"cannot-get-the-remote-user-name","errorCode":null,"errorMessage":"Cannot get the remote user name","messagePattern":"Cannot get the remote user name","errorType":"exception","errorClass":"AccessControlException","httpStatus":null,"severity":"error","filePath":"hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterPermissionChecker.java","lineNumber":118,"sourceCode":"\n  /**\n   * Check the superuser privileges of the current RPC caller. This method is\n   * based on Datanode#checkSuperuserPrivilege().\n   * @throws AccessControlException If the user is not authorized.\n   */\n  @Override\n  public void checkSuperuserPrivilege() throws  AccessControlException {\n\n    // Try to get the ugi in the RPC call.\n    UserGroupInformation ugi = null;\n    try {\n      ugi = NameNode.getRemoteUser();\n    } catch (IOException e) {\n      // Ignore as we catch it afterwards\n    }\n    if (ugi == null) {\n      LOG.error(\"Cannot get the remote user name\");\n      throw new AccessControlException(\"Cannot get the remote user name\");\n    }\n\n    // Is this by the Router user itself?\n    if (ugi.getShortUserName().equals(superUser)) {\n      return;\n    }\n\n    // Is the user a member of the super group?\n    if (ugi.getGroupsSet().contains(superGroup)) {\n      return;\n    }\n\n    // Not a superuser\n    throw new AccessControlException(\n        ugi.getUserName() + \" is not a super user\");\n  }\n}\n","sourceCodeStart":100,"sourceCodeEnd":136,"githubUrl":"https://github.com/apache/hadoop/blob/2add9630210752f88ceb1bb74eb65e37bf41da8e/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterPermissionChecker.java#L100-L136","documentation":"RouterPermissionChecker.checkSuperuserPrivilege first tries NameNode.getRemoteUser() to obtain the UGI of the current RPC caller. If that returns null (or throws and leaves ugi null) - meaning there is no remote user attached to this call context - the router logs the error and throws this AccessControlException: superuser checks cannot proceed without an authenticated caller.","triggerScenarios":"checkSuperuserPrivilege is executed outside a real RPC context, e.g. an in-process/embedded call into the admin or client protocol with no Server.getCurrent RPC attached, or a code path invoked during service lifecycle where getRemoteUser finds no call.","commonSituations":"Unit tests or embedded routers invoking protocol methods directly; custom tooling calling router methods locally instead of over RPC; rare degenerate calls during router startup/shutdown where the handler runs off the RPC thread.","solutions":["Invoke the router protocol over a real RPC connection (router:// or the router's RPC address) so a remote UGI exists","In tests, wrap the call in UserGroupInformation.createUserForTesting and run it through an RPC server, or use a client handle obtained from a started service","Ensure the call runs on the RPC handler thread; do not invoke protocol methods from lifecycle/other threads directly"],"exampleFix":"// before: direct in-process call, no RPC context\nrouterAdminServer.addMountTable(entry);   // AccessControlException: Cannot get the remote user name\n// after: call through the RPC client\nUserGroupInformation ugi = UserGroupInformation.createUserForTesting(\"hdfs\", new String[]{\"supergroup\"});\nugi.doAs((PrivilegedExceptionAction<Void>) () -> {\n  try (RouterClient client = new RouterClientFactory().createRouterAdminClient(conf, routerAdminAddress)) {\n    client.getMountTableAdmin().addMountTable(entry); \n  }\n  return null;\n});","handlingStrategy":"validation","validationCode":"// Ensure an RPC caller exists before invoking superuser-gated protocol methods\nUserGroupInformation caller = null;\ntry { caller = NameNode.getRemoteUser(); } catch (IOException ignored) { }\nif (caller == null) {\n  throw new IllegalStateException(\"No RPC context: invoke the router protocol over RPC, not in-process\");\n}","typeGuard":"boolean hasRemoteRpcCaller() {\n  try { return NameNode.getRemoteUser() != null; } catch (IOException e) { return false; }\n}","tryCatchPattern":"try {\n  protocol.checkSuperuserPrivilege(); // or the admin call that triggers it\n} catch (AccessControlException ace) {\n  if (\"Cannot get the remote user name\".equals(ace.getMessage())) {\n    // reissue over a real RPC connection as an authenticated user\n  }\n  throw ace;\n}","preventionTips":["Always drive router protocol methods through an RPC client, never direct in-process references","In tests, route calls through a started RPC server with a test UGI","Treat 'no remote user' as a wiring bug in the caller, not a permission problem to grant around"],"tags":["hdfs","router","federation","access-control","superuser","rpc-context"],"backgroundTag":"missing-authenticated-caller","analyzedSha":"2add9630210752f88ceb1bb74eb65e37bf41da8e","analyzedAt":"2026-08-22T19:55:07.957Z","schemaVersion":2},"datasetVersion":"2026-08-22T20:17:22.307Z"}