{"record":{"id":"7bc411f92e49e35d","repo":"hashicorp/nomad","slug":"error-opening-fifo-parent-directory-q-w","errorCode":null,"errorMessage":"error opening fifo parent directory %q: %w","messagePattern":"error opening fifo parent directory %q: %w","errorType":"error_code","errorClass":null,"httpStatus":null,"severity":"error","filePath":"client/lib/fifo/fifo_unix.go","lineNumber":38,"sourceCode":"// so it's advised to run it in a goroutine different from reader goroutine\nfunc CreateAndRead(path string) (func() (io.ReadCloser, error), error) {\n\t// create first\n\tif err := mkfifo(path, 0600); err != nil {\n\t\treturn nil, fmt.Errorf(\"error creating fifo %v: %w\", path, err)\n\t}\n\n\treturn func() (io.ReadCloser, error) {\n\t\treturn OpenReader(path)\n\t}, nil\n}\n\nfunc OpenReader(path string) (io.ReadCloser, 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 nil, fmt.Errorf(\"error opening fifo parent directory %q: %w\", dir, err)\n\t}\n\tdefer root.Close()\n\n\t// also uses O_NOFOLLOW under the hood\n\tf, err := root.OpenFile(base, os.O_RDONLY, 0)\n\tif err != nil {\n\t\treturn nil, fmt.Errorf(\"error opening reader at %s: %w\", path, err)\n\t}\n\treturn f, nil\n}\n\n// OpenWriter opens a fifo file for writer, assuming it already exists, returns io.WriteCloser\nfunc OpenWriter(path string) (io.WriteCloser, error) {\n\tdir := filepath.Dir(path)\n\tbase := filepath.Base(path)\n\n\troot, err := os.OpenRoot(dir)\n\tif err != nil {","sourceCodeStart":20,"sourceCodeEnd":56,"githubUrl":"https://github.com/hashicorp/nomad/blob/482b49bf1aec006f089bcfc7e632d8f6ac303e5e/client/lib/fifo/fifo_unix.go#L20-L56","documentation":"fifo.OpenReader opens the parent directory of the FIFO with os.OpenRoot before opening the FIFO itself, using openat2 with O_NOFOLLOW protections. This error wraps a failure opening the FIFO's parent directory, so the reader function cannot even attempt to open the FIFO.","triggerScenarios":"os.OpenRoot(dir) fails inside OpenReader because the directory does not exist (ENOENT — alloc dir cleaned up while reading), permissions deny access (EACCES), or path is not a directory (ENOTDIR, e.g. a file replaced the directory).","commonSituations":"Following Nomad logs while the allocation is garbage-collected concurrently; permissions on the alloc/logs directory changed (chmod/chown by operator); symlink or file substituted for the logs directory; NFS/overlay quirks returning unexpected errors.","solutions":["Re-run the open after confirming the alloc directory exists — if the allocation was GC'd, re-create the logs directory or restart the task.","Fix ownership/permissions on the alloc logs directory so the Nomad agent user can read it (e.g. chown -R nomad:nomad).","Verify the path component is a real directory, not a file or dangling symlink.","Check client data_dir for corruption; run nomad fs/alloc inspection or restart the client to rebuild alloc dirs."],"exampleFix":"// before: dir removed under the reader\n// EACCES on /var/lib/nomad/alloc/.../alloc/logs\n// after\n$ sudo chown -R nomad:nomad /var/lib/nomad/alloc\n$ nomad alloc logs <alloc_id>","handlingStrategy":"try-catch","validationCode":"func fifoDirReadable(path string) error {\n  dir := filepath.Dir(path)\n  st, err := os.Stat(dir)\n  if err != nil { return err }\n  if !st.IsDir() { return fmt.Errorf(\"%s is not a directory\", dir) }\n  return syscall.Access(dir, syscall.R_OK)\n}","typeGuard":"func fifoDirReady(path string) bool {\n  st, err := os.Stat(filepath.Dir(path))\n  return err == nil && st.IsDir() && syscall.Access(filepath.Dir(path), syscall.R_OK) == nil\n}","tryCatchPattern":"r, err := fifo.OpenReader(path)\nif err != nil {\n  var perr *fs.PathError\n  if errors.As(err, &perr) && errors.Is(perr.Err, syscall.ENOENT) {\n    // alloc was GC'd mid-read: recreate dir and retry once\n    os.MkdirAll(filepath.Dir(path), 0755)\n    r, err = fifo.OpenReader(path)\n  }\n  if err != nil { return nil, err }\n}","preventionTips":["Stop log followers before draining/GC'ing the allocation.","Keep alloc/logs directories owned by the Nomad agent user with readable permissions.","Verify the path is a directory, not a replaced file or dangling symlink.","Monitor client GC activity if log streaming is interrupted mid-read."],"tags":["linux","fifo","filesystem","logging"],"backgroundTag":"fifo-open-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"}