log

log

A lightweight logging wrapper for zerolog, providing convenience functions and sensible defaults for Interline and Transitland projects.

Note: This library is primarily intended for internal use across Interline/Transitland repositories—mainly for our convenience and to avoid having zerolog.Xyz scattered throughout our codebase and copy-pasting logging middlewares. It's published publicly for our convenience; external users should probably just use zerolog directly.

Features

• Simple printf-style logging functions (Infof, Debugf, Tracef, Errorf)
• Structured logging via zerolog's fluent API
• Pretty console output with colors (automatically disabled when piping/redirecting)
• JSON output mode for production environments
• Context-aware logging with request ID support
• HTTP middleware for request logging

Installation

go get github.com/interline-io/log

Usage

Basic Logging

package main

import "github.com/interline-io/log"

func main() {
    // Printf-style logging
    log.Infof("Processing %d items", 42)
    log.Debugf("Debug info: %s", "details")
    log.Errorf("Something went wrong: %v", err)
    log.Tracef("Verbose trace: %+v", obj)

    // Structured logging (zerolog style)
    log.Info().Str("user", "alice").Int("count", 5).Msg("User action")
    log.Error().Err(err).Str("op", "save").Msg("Operation failed")

    // Simple print (no timestamp, ignores log level)
    log.Print("Plain output: %s", "hello")
}

Context-Aware Logging

// Get logger from context
logger := log.For(ctx)
logger.Info().Msg("Using context logger")

// Add logger to context
ctx = log.WithLogger(ctx, customLogger)

HTTP Middleware

import "github.com/interline-io/log"

// Add request ID to each request
r.Use(log.RequestIDMiddleware)

// Add request ID to context logger
r.Use(log.RequestIDLoggingMiddleware)

// Log request duration and details
r.Use(log.LoggingMiddleware(1000, getUserNameFunc))

Configuration

Environment Variables

Examples

# Enable debug logging
TL_LOG=DEBUG ./myapp

# Enable trace logging (most verbose)
TL_LOG=TRACE ./myapp

# JSON output for production/log aggregation
TL_LOG_JSON=true ./myapp

Terminal Colors

Console output includes ANSI colors when writing to a terminal. Colors are automatically disabled when output is piped or redirected:

# Colors enabled (terminal)
./myapp

# Colors disabled (piped)
./myapp | tee output.log

# Colors disabled (redirected)
./myapp > output.log 2>&1

Log Levels

License

See LICENSE file.