This bash script provides a straightforward method for achieving zero-downtime deployment with various NodeJS frameworks, and it can also automate the deployment process for other types of applications.

For reading deploy.config.json configuration, additional packages is required.

To install Ubuntu/Debian

sudo apt-get install jq

To install on Fedora/CentOS

sudo dnf install jq

Download deployer.sh, move it in your project directory (see usage), or install globally by moving to /usr/local/bin

In this example we have application written over NuxtJS, serve it using Nginx.

We want to implement green/blue (zero-downtime) deployment on this application.

First, define the upstream in Nginx with sample configuration

upstream backend {
    server 127.0.0.1:3000 fail_timeout=0;
    server 127.0.0.1:3001 fail_timeout=0;
}

Then, in server directive, change the location as follows

location / {
    proxy_pass                          http://backend; # set the address of the Node.js instance here
    proxy_next_upstream error timeout   invalid_header http_500;
    proxy_connect_timeout               2;
    proxy_set_header Host               $host;
    proxy_set_header X-Real-IP          $remote_addr;
    proxy_set_header X-Forwarded-For    $proxy_add_x_forwarded_for;
    proxy_redirect                      off;
    proxy_buffering off;
}

Application is running in daemon mode using supervisord with two configurations as follows

example.blue.conf

[program:myapp-blue]
directory=/home/myapp/blue/
command=/bin/bash -c 'nuxt start'
user=myapp
autostart=true
autorestart=true
redirect_stderr=true
stdout_logfile=/var/log/supervisor/myapp-blue.log

example.green.conf

[program:myapp-green]
directory=/home/myapp/green/
command=/bin/bash -c 'nuxt start'
user=myapp
autostart=true
autorestart=true
redirect_stderr=true
stdout_logfile=/var/log/supervisor/myapp-green.log

Structure of application will be following:

/home/
    /myapp/
        /green/
            myapp.js
        /blue
            myapp.js
        deploy.config.json

Configuration deploy.config.json must be in directory near green and blue

{
  "current":"green",
  "commands":{
    "prepare":[
      "git pull"
    ],
    "install":[
      "npm i"
    ],
    "build":[
      "npm run build"
    ],
    "restart":[
      "supervisorctl start merchant-#NEXT_COLOR#",
      "supervisorctl stop merchant-#CURRENT_COLOR#"
    ]
  },
  "logging":{
    "enabled":true,
    "file":"deploy.log"
  }
}

To list all available commands, use

deployer.sh -h
Tool used to implement zero downtime deployment.

Syntax: deployer.sh [-i|v|c|h]
Options:
c  Echo current color.
i  Run commands from 'commands.install' group immediately after prepare
v  Print version.

To run the deployment process, run following command in directory with configuration, and wait for process to complete

cd /home/myapp && deployer.sh

This package is open-sourced software licensed under the MIT license.