caddy-supervisor

caddy-supervisor

Introduction

This plugin enables caddy to run and supervise background processes.

How it works

For every supervisor caddy directive a command is executed in background and killed when caddy stops.

You can use supervisor plugin as an http directive or as a server type.

Supervisor http directive

You can activate a supervisor directly from your web caddyfile using:

supervisor command arg1 arg2 arg3

Or using a block for more control

supervisor {
  command command
  args arg1 arg2 arg3
  dir directory
  env VARIABLEA=VALUEA
  env VARIABLEB=VALUEB
  redirect_stdout file
  redirect_stderr file
  restart_policy policy
  termination_grace_period period
}

Supervisor server type

You can also use a supervisor server type using -type CLI option:

caddy -type supervisor

The Caddyfile syntax for supervisor server type is:

name {
  command command
  args arg1 arg2 arg3
  dir directory
  env VARIABLEA=VALUEA
  env VARIABLEB=VALUEB
  redirect_stdout file
  redirect_stderr file
  restart_policy policy
  termination_grace_period period
}
...

Options description

• command: the command or executable name to be executed
• args: args provided to the command, separated by whitespace
• dir: the working directory the command should be executed in
• env: declare environment variable that should be passed to command. This property can be repeated
• redirect_stdout: redirect command stdout to a file. Use "stdout" to redirect to caddy stdout
• redirect_stderr: redirect command stderr to a file. Use "stderr" to redirect to caddy stderr
• restart_policy: define under which conditions the command should be restarted after exit. Valid values:
  • never: do not restart the command
  • on_failure: restart if exit code is not 0
  • always: always restart
• termination_grace_period: amount of time to wait for application graceful termination before killing it. Ex: 10s

On windows termination_grace_period is ignored and the command is killed immediatelly due to lack of signals support.

Exponential backoff

To avoid spending too many resources on a crashing application, this plugin makes use of exponential backoff.

That means that when the command exits, it will be restarted with a delay of 10 seconds. On every successive exit, the delay time doubles, with a max limit of 5 minutes.

If the command runs stable for at least 10 minutes, the restart delay is reset to 10 seconds.

Examples

AspNet Core application on windows:

example.com {
  run {
    env ASPNETCORE_URLS=http://localhost:5000
    command dotnet ./MyApplication.dll
    dir "C:\MyApplicationFolder"
    redirect_stdout stdout
    redirect_stderr stderr
    restart_policy always
  }
  proxy / localhost:5000 {
    transparent
  }
}

Php fastcgi on windows:

example.com {
  run {
    command ./php-cgi.exe
    args -b 9800
    dir C:/php/
    redirect_stdout stdout
    redirect_stderr stderr
    restart_policy always
  }
  root C:/Site
  fastcgi / localhost:9800 php
}

Building it

Build from caddy repository and import caddy-supervisor plugin on file https://github.com/mholt/caddy/blob/master/caddy/caddymain/run.go :

import (
  _ "github.com/lucaslorentz/caddy-supervisor/httpplugin"
  _ "github.com/lucaslorentz/caddy-supervisor/servertype"
)