{"record":{"id":"d8568a15c45c0aed","repo":"Billionmail/BillionMail","slug":"imagemagick-thumbnail-failed-w-output-s","errorCode":null,"errorMessage":"imagemagick thumbnail failed: %w\noutput: %s","messagePattern":"imagemagick thumbnail failed: %w\noutput: (.+?)","errorType":"error_code","errorClass":null,"httpStatus":null,"severity":"error","filePath":"core/internal/service/video_gen/thumbnail.go","lineNumber":65,"sourceCode":"\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":47,"sourceCodeEnd":70,"githubUrl":"https://github.com/Billionmail/BillionMail/blob/fc36c76c050c3775c5e899faf7403cf0262d2744/core/internal/service/video_gen/thumbnail.go#L47-L70","documentation":"GenerateThumbnail shells out to ImageMagick's 'magick' CLI via exec.CommandContext to produce a video thumbnail, capturing combined stdout/stderr. When the command exits non-zero (or the binary cannot be found/executed), the underlying error is wrapped as 'imagemagick thumbnail failed: %w' with the full CLI output appended, so both the Go-level failure and ImageMagick's own diagnostics are preserved in one message.","triggerScenarios":"magick is not installed or not on PATH (exec.ErrNotFound via CombinedOutput); the input video path does not exist or is unreadable (as tested by TestGenerateThumbnail_NonexistentInput); the supplied thumbnail args are malformed; or the context is cancelled before magick finishes (TestGenerateThumbnail_CancelledContext), causing Wait to fail with a context/deadline error.","commonSituations":"Minimal Docker images without imagemagick installed; ImageMagick 6 environments that ship the binary as 'convert' instead of 'magick'; video files in formats magick cannot delegate to ffmpeg; missing file permissions; pipeline shutdown cancelling the context mid-conversion.","solutions":["Install ImageMagick (apt-get install imagemagick / apk add imagemagick) and confirm 'magick -version' works inside the container","Run the exact args from BuildThumbnailArgs(cfg) by hand to inspect ImageMagick's output printed after 'output:' in the error","Verify the input video path exists and is readable before calling GenerateThumbnail","If running ImageMagick 6, either upgrade to IM7 or adapt BuildThumbnailArgs to invoke 'convert'","Check context cancellation: if the pipeline is being shut down, the wrapped error will be context.Canceled"],"exampleFix":"// before\ncmd := exec.CommandContext(ctx, \"magick\", args...)\nout, err := cmd.CombinedOutput()\n// after\nif _, err := exec.LookPath(\"magick\"); err != nil {\n    return \"\", fmt.Errorf(\"imagemagick not found on PATH: %w\", err)\n}\ncmd := exec.CommandContext(ctx, \"magick\", args...)\nout, err := cmd.CombinedOutput()","handlingStrategy":"validation","validationCode":"if _, err := exec.LookPath(\"magick\"); err != nil {\n    return fmt.Errorf(\"thumbnail prerequisite missing: install imagemagick: %w\", err)\n}\nif info, err := os.Stat(inputVideoPath); err != nil || info.IsDir() {\n    return fmt.Errorf(\"input video not readable: %s\", inputVideoPath)\n}\nif ctx.Err() != nil {\n    return ctx.Err()\n}","typeGuard":null,"tryCatchPattern":"urls, err := GenerateThumbnail(ctx, cfg)\nif err != nil {\n    var execErr *exec.ExitError\n    switch {\n    case errors.Is(err, context.Canceled):\n        // pipeline shutdown; do not retry\n    case errors.As(err, &execErr):\n        log.Errorf(\"magick failed: %v\", err) // output is embedded in the message\n    default:\n        log.Errorf(\"thumbnail error: %v\", err)\n    }\n}","preventionTips":["Bake imagemagick into the deployment image and check 'magick -version' at container startup","Add an exec.LookPath('magick') preflight in service init","Always stat input files before invoking GenerateThumbnail","Keep BuildThumbnailArgs covered by unit tests so arg changes fail fast"],"tags":["imagemagick","exec","external-command","thumbnail"],"backgroundTag":"external-command-failed","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"}