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Health Check Nginx Docker image

Just simple docker image running NginX responding to:

/                  # 404 Not Found
/health-check      # 200 OK
/health-check.html # 200 OK
/healthcheck       # 200 OK
/healthcheck.html  # 200 OK

Usage example

This is docker image is useful if you are configuring server that is running a worker server running background tasks independent of the Web-Server.

That means that the BG server does not necessary need to respond to http requests yet you still want to expose http health-check endpoint that can be pinged.

docker pull equivalent/health_check_nginx:1.0
# ..or
docker pull equivalent/health_check_nginx:latest

docker run -p 80:80 -d equivalent/health_check_nginx

curl -v localhost/                  # 404 Not Found
curl -v localhost/health-check      # 200 OK
curl -v localhost/health-check.html # 200 OK
curl -v localhost/healthcheck       # 200 OK
curl -v localhost/healthcheck.html  # 200 OK

AWS Elastic Beanstalk example

If you have AWS ElasticBeanstalk enviroment (EB), you can configure "healthcheck endpoint" (e.g.: http://my-enviromnet-app.elasticbeanstalk.com/health-check.html).

When that healthcheck is not responding with Status 200 AWS EB will remove that instance from load balancer or it will raise "red" flang in server monitoring.

Now here is the useful part. When you are running Docker environment on AWS ElasticBeanstalk if any of your esential containers is failing (e.g. memory leak) EB will retriger EB job. That means it effectively restarts all docker containers in the definition. So this Nginx health-check container will restart as well.

Dockerrun.aws.json

{
  "AWSEBDockerrunVersion": 2,

  "containerDefinitions": [
    {
      "name": "background-worker",
      "image": "my-company/my-bg-worker-app",
      "essential": true
    },
    {
      "name": "health_check_nginx",
      "image": "equivalent/health_check_nginx",
      "essential": true,
      "portMappings": [
        {
          "hostPort": 80,
          "containerPort": 80
        }
      ]
    }
  ]
}

Other examples

Just make sure that when your "primary" docker image (e.g. BG worker) goes down it will bring down this docker container as well (e.g. specify in docker-compose.yml specify depends_on: my_bg_worker for this container.

Building docker on your local machine

git clone [email protected]:equivalent/health_check_nginx_docker.git
docker build -t=nginx-health .
docker run -p 80:80 -it nginx-health