kpacha/varnish repository overview

⁠varnish-docker

A minimal varnish container for mesos environments.

⁠Running outside mesos

Just run the docker image with your customized the env vars:

docker run -it --rm -e "VARNISH_BACKEND_ADDRESS=140.211.11.105" \
    -e "VARNISH_BACKEND_HOSTNAME=www.apache.org" \
    -p 80:80 kpacha/varnish

⁠Running in mesos

If you have mesos-dns and bamboo, follow this simple steps:

• associate the A Record of the backend app with the backend using bamboo, so bamboo will handle all the redirections
• create a new app in the service group for the varnish instance. See below for an example.
• associate the public A Record of your service to the varnish app, so bamboo will handle all the redirections

⁠Example

Create your backend app for the example service

$ curl -iXPOST -d '{
      "id": "example/http",
      "cmd": "python -m SimpleHTTPServer \$PORT",
      "mem": 50,
      "cpus": 0.1,
      "instances": 1,
      "constraints": [
        ["hostname", "UNIQUE"]
      ]
    }' http://marathon.mesos:8080/v2/apps

Associate the A Record of the new app with the app itself in the bamboo config

$ curl -iXPOST -d '{"id":"/example/http","acl":"hdr(host) -i http-example.marathon.mesos"}' \
    http://slave.mesos:8000/api/services

Create the varnish app for the example service

$ curl -iXPOST -d '{
      "id": "example/varnish",
      "mem": 300,
      "cpus": 0.5,
      "instances": 2,
      "cmd": "VARNISH_BACKEND_ADDRESS=\$HOST sh /start.sh",
      "constraints": [
        ["hostname", "UNIQUE"]
      ],
      "container": {
        "type": "DOCKER",
        "network": "BRIDGE",
        "portMappings": [
            {
                "containerPort": 80,
                "hostPort": 0,
                "servicePort": 0
            }
        ],
        "docker": {
          "image": "kpacha/varnish"
        }
      },
      "env": {
        "VARNISH_BACKEND_HOSTNAME": "http-example.marathon.mesos",
      }
    }' http://marathon.mesos:8080/v2/apps

Associate the public A Record of the service with the varnish app in the bamboo config

$ curl -iXPOST -d '{"id":"/example/varnish","acl":"hdr(host) -i www.example.com"}' \
    http://slave.mesos:8000/api/services

⁠Tips

⁠Single backend

It's recommended to set the VARNISH_BACKEND_ADDRESS env var to $HOST so each one of the varnish instances use the nearest HAProxy instance as a single backend.

Using the A Record of the backend service directly would force you the define several probes and a director, messing the vcl and adding lots of complexity to the cache layer.

⁠Instance number

Set as many varnish instances as you require (the more instances you set, the higher service throughput you get) but remember, even when marathon is monitoring your apps, service discontinuations could happen if your app has just one instance and that instance fails, so the recommended min is 2.

⁠Configuration

The image use these environmental vars:

• VARNISH_BACKEND_ADDRESS: single ip of the backend service or load balancer
• VARNISH_MEMORY: amount of memory to allocate for caching
• VARNISH_BACKEND_PORT: port of the backend service
• VARNISH_VCL_FILE: path to the vcl file
• VARNISH_PROBE_INTERVAL: interval between healthcheck requests
• VARNISH_PROBE_TIMEOUT: timeout for the healthcheck requests
• VARNISH_GRACE_TIME: max time for serving stale content

Check the Dockerfile for the default values