fastlog

fastlog

Import path: github.com/InsideGallery/core/fastlog

fastlog builds and installs structured log/slog handlers from environment-backed configuration. It fans out to registered output handlers, applies built-in middleware, and can replace slog.Default().

Main APIs

• Config describes logging outputs, level, and middleware toggles.
• GetConfigFromEnv() reads LOG_* environment variables.
• (*Config).GetHandler(m ...slogmulti.Middleware) builds a composite slog.Handler.
• SetupDefaultLogger(cfg *Config, m ...slogmulti.Middleware) installs the handler as slog.Default().

Usage

package example

import (
	"log/slog"

	_ "github.com/InsideGallery/core/fastlog/all"

	"github.com/InsideGallery/core/fastlog"
	"github.com/InsideGallery/core/fastlog/middlewares"
)

func configureLogging() error {
	cfg, err := fastlog.GetConfigFromEnv()
	if err != nil {
		return err
	}

	if err := fastlog.SetupDefaultLogger(cfg, middlewares.NewGDPRMiddleware()); err != nil {
		return err
	}

	slog.Info("logging configured")

	return nil
}

Configuration

GetConfigFromEnv uses the LOG prefix:

• LOG_OUTPUTS: comma-separated kind:format values, default stderr:json.
• LOG_LEVEL: parsed as a slog.Level, default INFO.
• LOG_CALLER: adds a caller attribute when true, default true.
• LOG_ERROR_FORMATTING: converts error attributes to structured groups when true, default false.

Valid formats are json and text; unknown formats fall back to JSON. Malformed output entries are skipped. Unknown handlers are collected as errors, and if no handler can be built the package falls back to the registered nop handler.

The base package imports only the nop fallback directly. Import fastlog/all or the specific handler packages before selecting stderr, datadog, or otel through LOG_OUTPUTS.