go/docs/pkg/log.md

Log Retention Policy

The log package provides structured logging with automatic log rotation and retention management.

Retention Policy

By default, the following log retention policy is applied when log rotation is enabled:

• Max Size: 100 MB per log file.
• Max Backups: 5 old log files are retained.
• Max Age: 28 days. Old log files beyond this age are automatically deleted. (Set to -1 to disable age-based retention).
• Compression: Rotated log files can be compressed (future feature).

Configuration

Logging can be configured using the log.Options struct. To enable log rotation to a file, provide a RotationOptions struct. If both Output and Rotation are provided, Rotation takes precedence and Output is ignored.

Standalone Usage

logger := log.New(log.Options{
    Level: log.LevelInfo,
    Rotation: &log.RotationOptions{
        Filename:   "app.log",
        MaxSize:    100, // MB
        MaxBackups: 5,
        MaxAge:     28, // days
    },
})

logger.Info("application started")

Framework Integration

When using the Core framework, logging is usually configured during application initialization:

app, _ := core.New(
    core.WithName("log", log.NewService(log.Options{
        Level: log.LevelDebug,
        Rotation: &log.RotationOptions{
            Filename: "/var/log/my-app.log",
        },
    })),
)

How It Works

1. Rotation: When the current log file exceeds MaxSize, it is rotated. The current file is renamed to filename.1, filename.1 is renamed to filename.2, and so on.
2. Retention:
   • Files beyond MaxBackups are automatically deleted during rotation.
   • Files older than MaxAge days are automatically deleted during the cleanup process.
3. Appends: When an application restarts, it appends to the existing log file instead of truncating it.