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Logging in Go Applications: Best Practices and Tools

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Logging in Go Applications: Best Practices



Logging is one of the cornerstones of any production application. It helps track errors, analyze system behavior, and perform audits. In Go, thanks to its simplicity and performance, the approach to logging has its own characteristics. In this article, we will break down the best practices for logging in Go (Golang), review popular libraries, and provide code examples that will help you build a reliable monitoring system.



Why is the standard log package not always the best choice?



The built-in log package in Go is simple and convenient for basic tasks. However, for production applications, it has a number of limitations:



  • Lack of logging levels (debug, info, warn, error).
  • No support for structured data (JSON, key-value).
  • Difficulties with output configuration (e.g., to multiple files or a log collection system).
  • Potential performance issues under high load.


For serious projects, it is recommended to use one of the specialized libraries.



Best Libraries for Logging in Go



In the Go ecosystem, there are several well-established libraries. Let's look at the three most popular ones:



1. Logrus

One of the first libraries that brought structured logging to Go. Logrus supports levels, formatting (JSON, Text), and hooks for integration with external services (e.g., Sentry).



package main

import (    "github.com/sirupsen/logrus")

func main() {    log := logrus.New()    log.SetFormatter(&logrus.JSONFormatter{})    log.SetLevel(logrus.DebugLevel)

    log.WithFields(logrus.Fields{        "user_id": 123,        "action": "login",    }).Info("User logged into the system")}


2. Zap (Uber)

Zap from Uber is a high-performance library focused on speed. It offers two APIs: SugaredLogger (convenient, slightly slower) and Logger (maximum performance). Zap is ideal for high-load services.



package main

import (    "go.uber.org/zap")

func main() {    logger, _ := zap.NewProduction()    defer logger.Sync() // flushes buffer, if any

    logger.Info("Request processed",        zap.String("path", "/api/v1/users"),        zap.Int("status", 200),        zap.Duration("duration", 0.5),    )}


3. Zerolog

Zerolog is another library focused on performance and minimal memory allocation. It provides a fluent API and excellent support for JSON logs out of the box.



package main

import (    "github.com/rs/zerolog"    "github.com/rs/zerolog/log")

func main() {    zerolog.TimeFieldFormat = zerolog.TimeFormatUnix

    log.Debug().        Int("user_id", 456).        Str("role", "admin").        Msg("Received request for deletion")}


Best Practices for Logging in Go



Regardless of the chosen library, it is worth following these rules:



1. Use structured logs (JSON)

Text logs are difficult to parse and analyze. The JSON format allows easy integration with log collection systems (ELK, Loki, Datadog) and enables complex queries.



// Badlog.Printf("User %d logged in", userID)

// Good (with Zap)logger.Info("user logged in", zap.Int("user_id", userID))


2. Choose the logging level correctly