Log to STDOUT and STDERR when Running NGINX in the Foreground

April 19, 2014

This is somewhat of a follow-up to this post:

http://tastehoneyco.com/blog/running-nginx-in-the-foreground/

The instructions there are simple enough and it works great, but no output is logged while NGINX is running. This can be annoying if you like treating logs as streams rather than as something that ends up in a file on a (probably transient) filesystem. Unfortunately there doesn’t seem to be a way to do this through the NGINX config, probably because it doesn’t fit with the typical NGINX paradigm (a service running in the background with master / worker processes). However, I want to do it anyway. I created a simple go script to handle this:

package main

import (
    "fmt"
    "os/exec"
    "os"
    "github.com/ActiveState/tail"
)

func Nginx(c chan int) {
  pwd, _ := os.Getwd()
  conf   := pwd + "/nginx.conf"
  cmd := exec.Command("nginx", "-c", conf)
  cmd.Stdout = os.Stdout
  cmd.Stderr = os.Stderr
  cmd.Run()
}

func AcessLog(c chan int) {
  t, _ := tail.TailFile("/path/to/nginx/logs/nginx-access.log", tail.Config{Follow: true})

  for line := range t.Lines {
    fmt.Println(line.Text)
  }
}

func ErrorLog(c chan int) {
  t, _ := tail.TailFile("/path/to/nginx/logs/nginx-error.log", tail.Config{Follow: true})

  for line := range t.Lines {
    fmt.Fprintln(os.Stderr, line.Text)
  }
}

func main() {
    c := make(chan int)
    go Nginx(c)
    go AcessLog(c)
    go ErrorLog(c)

    nginx  := <- c
    access := <- c
    error  := <- c

    fmt.Println(nginx)
    fmt.Println(access)
    fmt.Println(error)
    fmt.Println("done.")
}

All this is doing is setting up 3 goroutines, 1 for the nginx master process, 1 for a tail of the error log which gets printed to STDERR, and 1 for the access log which gets printed to STDOUT. This requires some additional config in the NGINX config:

worker_processes  1;
daemon off;

events {
  worker_connections 1024;
}

http {
  access_log /path/to/nginx/logs/nginx-access.log;
  error_log  /path/to/nginx/logs/nginx-error.log debug;

  server {
    listen 8080;
  }
}

As you can see I’ve increased the log level to debug to get the maximum amount of information from NGINX. That’s it! Try running the go script, and you should see requests and errors showing up in the terminal as they are made.