Log Management

Runix captures stdout and stderr from every managed process into separate log files with optional rotation.

Log Storage

~/.runix/apps/<name>/
├── stdout.log     # Captured stdout
└── stderr.log     # Captured stderr

Log Format

Each line is prefixed with a timestamp and source marker by the PrefixWriter:

2025-01-15 10:30:00 [out] Server listening on :8080
2025-01-15 10:30:01 [out] Connected to database
2025-01-15 10:30:05 [err] Connection timeout to redis
2025-01-15 10:30:06 [err] Retry attempt 1/3

Implementation

Capture

Process output is captured via exec.Cmd pipes:

1. cmd.StdoutPipe() → connected to a PrefixWriter wrapping the log file
2. cmd.StderrPipe() → connected to a separate PrefixWriter
3. Each writer prepends timestamps and [out]/[err] markers
4. Writes are mutex-protected for thread safety

Rotation

Located at internal/logrot/rotator.go, the Rotator provides size-based log rotation:

func NewRotator(path string, maxSize int64, maxFiles int, maxAge time.Duration) (*Rotator, error)

Configuration

processes:
  api:
    entrypoint: ./cmd/api
    logging:
      max_size: 10485760   # 10MB in bytes
      max_files: 5          # Keep 5 rotated files
      max_age: 168h         # 7 days

Rotation Process

1. Before each write, check if current_size + write_size >= max_size
2. If so, rotate:
   • Close the current file
   • Rename to <name>.log.<timestamp> (e.g., stdout.log.2025-01-15T10-30-00)
   • Open a new file at the original path
   • Prune old files
3. Pruning removes files exceeding max_files count or max_age duration

Pruning Rules

Rule	Behavior
max_files > 0	Keep only the N newest rotated files
max_age > 0	Remove files older than the duration
Both	Both rules applied

Default Values

Setting	Default
max_size	10MB (10,485,760 bytes)
max_files	5
max_age	168h (7 days)

Log Commands

# View last 50 lines
runix logs api

# Stream live output
runix logs api --follow

# View stderr
runix logs api --stderr

# Error lines only
runix logs api --error

# Truncate log files
runix flush api
runix flush           # All apps

What's Next

• Logs Command — CLI usage
• Flush Command — Clear log files
• Configuration Reference — Logging config fields