{"record":{"id":"c6596c559f3e1112","repo":"hashicorp/nomad","slug":"error-getting-file-handle-to-fifo-parent-directory","errorCode":null,"errorMessage":"error getting file handle to fifo parent directory %q: %v","messagePattern":"error getting file handle to fifo parent directory %q: (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"client/lib/fifo/mkfifoat.go","lineNumber":28,"sourceCode":"\t\"os\"\n\t\"path/filepath\"\n\n\t\"golang.org/x/sys/unix\"\n)\n\nfunc mkfifo(path string, mode uint32) (err error) {\n\tdir := filepath.Dir(path)\n\tbase := filepath.Base(path)\n\n\troot, err := os.OpenRoot(dir)\n\tif err != nil {\n\t\treturn fmt.Errorf(\"error opening fifo parent directory %q: %v\", dir, err)\n\t}\n\tdefer root.Close()\n\n\tparent, err := root.Open(\".\")\n\tif err != nil {\n\t\treturn fmt.Errorf(\"error getting file handle to fifo parent directory %q: %v\", dir, err)\n\t}\n\tdefer parent.Close()\n\n\t// os.Root doesn't support creating a FIFO, so we need to drop to the\n\t// syscall and grab the parent's FD\n\terr = unix.Mkfifoat(int(parent.Fd()), base, mode)\n\tif err != nil {\n\t\treturn fmt.Errorf(\"error creating fifo: %w\", err)\n\t}\n\treturn nil\n}\n","sourceCodeStart":10,"sourceCodeEnd":40,"githubUrl":"https://github.com/hashicorp/nomad/blob/482b49bf1aec006f089bcfc7e632d8f6ac303e5e/client/lib/fifo/mkfifoat.go#L10-L40","documentation":"After opening the parent directory with os.Root, this mkfifo variant calls root.Open(\".\") to obtain a file handle to the parent directory itself, needed because os.Root does not expose mkfifoat. This error is returned when opening that handle fails, even though OpenRoot succeeded — an unexpected internal I/O failure (e.g. the directory was removed concurrently, or fd/handle limits hit).","triggerScenarios":"Calling fifo.Create when the parent directory is deleted between OpenRoot and root.Open(\".\"), the handle is denied by the OS, or the process is out of file descriptors (EMFILE/ENFILE).","commonSituations":"Concurrent cleanup deleting the runtime dir while IO setup runs; fd leaks exhausting the descriptor limit in long-running daemons; exotic filesystems not supporting opening directories.","solutions":["Re-run creation; retry usually succeeds if a concurrent removal raced","Raise the file-descriptor limit (ulimit -n / systemd LimitNOFILE) if EMFILE/ENFILE","Ensure no concurrent cleanup deletes the parent directory during IO setup","Upgrade the library / check filesystem support if the FS cannot open directory handles"],"exampleFix":"// before\n// assuming fd exhaustion\nif err := fifo.Create(path, mode); err != nil { return err }\n// after\nif err := fifo.Create(path, mode); err != nil {\n\tif errors.Is(err, syscall.EMFILE) || errors.Is(err, syscall.ENFILE) {\n\t\treturn fmt.Errorf(\"fd limit reached; raise LimitNOFILE: %w\", err)\n\t}\n\treturn err\n}","handlingStrategy":"retry","validationCode":null,"typeGuard":null,"tryCatchPattern":"err := fifo.Create(path, mode)\nif err != nil {\n\tif isFdExhaustion(err) { // EMFILE/ENFILE\n\t\t// raise limit or free fds, then retry\n\t}\n\treturn err\n}","preventionTips":["Avoid concurrent teardown of the parent directory during IO setup","Monitor fd usage; raise LimitNOFILE in long-running daemons","Fix fd leaks so EMFILE does not occur","Retry transient failures of the create call"],"tags":["go","linux","fifo","file-descriptors"],"backgroundTag":"fifo-create-failed","analyzedSha":"482b49bf1aec006f089bcfc7e632d8f6ac303e5e","analyzedAt":"2026-09-04T07:54:14.808Z","contentChangedAt":"2026-09-04T07:54:14.808Z","schemaVersion":2},"datasetVersion":"2026-09-08T10:18:20.063Z"}