{"record":{"id":"b003a84c3bedc459","repo":"Billionmail/BillionMail","slug":"create-thumbnail-dir-w","errorCode":null,"errorMessage":"create thumbnail dir: %w","messagePattern":"create thumbnail dir: %w","errorType":"error_code","errorClass":null,"httpStatus":null,"severity":"error","filePath":"core/internal/service/video_gen/thumbnail.go","lineNumber":58,"sourceCode":"\t}\n\th := cfg.Height\n\tif h == 0 {\n\t\th = defaultThumbHeight\n\t}\n\n\treturn []string{\n\t\tcfg.InputPath,\n\t\t\"-resize\", fmt.Sprintf(\"%dx%d!\", w, h),\n\t\t\"-quality\", \"90\",\n\t\tcfg.OutputPath,\n\t}\n}\n\n// GenerateThumbnail creates a thumbnail from a screenshot using ImageMagick.\n// Requires: magick (ImageMagick) installed.\nfunc GenerateThumbnail(ctx context.Context, cfg ThumbnailConfig) (string, error) {\n\tif err := os.MkdirAll(filepath.Dir(cfg.OutputPath), 0755); err != nil {\n\t\treturn \"\", fmt.Errorf(\"create thumbnail dir: %w\", err)\n\t}\n\n\targs := BuildThumbnailArgs(cfg)\n\tcmd := exec.CommandContext(ctx, \"magick\", args...)\n\tout, err := cmd.CombinedOutput()\n\tif err != nil {\n\t\treturn \"\", fmt.Errorf(\"imagemagick thumbnail failed: %w\\noutput: %s\", err, string(out))\n\t}\n\n\treturn cfg.OutputPath, nil\n}\n","sourceCodeStart":40,"sourceCodeEnd":70,"githubUrl":"https://github.com/Billionmail/BillionMail/blob/fc36c76c050c3775c5e899faf7403cf0262d2744/core/internal/service/video_gen/thumbnail.go#L40-L70","documentation":"GenerateThumbnail creates the parent directory of cfg.OutputPath via os.MkdirAll before invoking ImageMagick. If directory creation fails (permissions, read-only fs, path is a file), the OS error is wrapped with 'create thumbnail dir: %w'.","triggerScenarios":"os.MkdirAll(filepath.Dir(cfg.OutputPath), 0755) fails: the parent of OutputPath is unwritable, already exists as a file, disk is full, or an invalid path segment is supplied.","commonSituations":"Same writable-volume issues as screenshot output in Docker; OutputPath built by joining a bad/empty base dir so Dir() resolves to an unwritable location; non-root process user lacking permissions.","solutions":["Inspect the wrapped OS error for the exact filesystem cause","Ensure the thumbnail output directory exists and is writable by the process user","Mount a writable volume for output paths in containers","Verify OutputPath is constructed correctly (non-empty base dir, directory not a file)"],"exampleFix":"// before\nif err := os.MkdirAll(filepath.Dir(cfg.OutputPath), 0755); err != nil {\n\treturn \"\", fmt.Errorf(\"create thumbnail dir: %w\", err)\n}\n// after\noutDir := filepath.Dir(cfg.OutputPath)\nif info, err := os.Stat(outDir); err == nil && !info.IsDir() {\n\treturn \"\", fmt.Errorf(\"thumbnail output path %q is a file, not a directory\", outDir)\n}\nif err := os.MkdirAll(outDir, 0755); err != nil {\n\treturn \"\", fmt.Errorf(\"create thumbnail dir: %w\", err)\n}","handlingStrategy":"validation","validationCode":"outDir := filepath.Dir(cfg.OutputPath)\nif outDir == \".\" || outDir == \"\" {\n\treturn fmt.Errorf(\"thumbnail output path has no directory component\")\n}\nif info, err := os.Stat(outDir); err == nil && !info.IsDir() {\n\treturn fmt.Errorf(\"%s is a file\", outDir)\n}","typeGuard":null,"tryCatchPattern":"path, err := GenerateThumbnail(ctx, cfg)\nif err != nil && strings.HasPrefix(err.Error(), \"create thumbnail dir:\") {\n\tvar perr *fs.PathError\n\tif errors.As(err, &perr) && errors.Is(perr.Err, fs.ErrPermission) {\n\t\treturn fmt.Errorf(\"cannot write thumbnails to %s: check volume mount/permissions\", filepath.Dir(cfg.OutputPath))\n\t}\n}","preventionTips":["Derive thumbnail output paths from the same writable volume as screenshot output","Pre-create output directories during deployment","Run tests (e.g. TestGenerateThumbnail_NonexistentInput) in CI to catch path bugs early","Avoid empty/relative base dirs when composing OutputPath"],"tags":["filesystem","permissions","directory","imagemagick","io"],"backgroundTag":"filesystem-permission-denied","analyzedSha":"fc36c76c050c3775c5e899faf7403cf0262d2744","analyzedAt":"2026-09-05T21:28:54.019Z","contentChangedAt":"2026-09-05T21:28:54.019Z","schemaVersion":2},"datasetVersion":"2026-09-12T22:17:10.623Z"}