etcd-vhost

A virtual-hosting proxy configured using etcd. It is designed to simplify web service discovery and vhost setups on clustered hosts like CoreOS.

          Load Balancer
               ||
        -----------------
        |               |
        V               V
  etcd-vhost          etcd-vhost
        |               |
        -----------------
               ||
        -----------------
        |               |
        V               V
  Web App 1           Web App 2

Features

• Uses etcd for service discovery, e.g. adding a target host for the vhost "www.example.com":
  • key: /etcd_vhost/vhosts/www.example.com/10.0.0.1:8080
  • value: "http://10.0.0.1:8080"
• Multiple targets for a single vhost, which will be accessed in a round-robin fashion

Usage

You can run the vhost proxy as a docker container or as a stand-alone node app. The docker container will be run with the argument --etcd-hosts=172.17.42.1:4001, which is the default docker host on the docker0 interface.

Running the server with Docker

docker run ronalddddd/etcd-vhost

Running the server with NPM

    # Install
    npm install etcd-vhost

    # Run
    npm start --port=8080 --etcd-hosts=127.0.0.1:4001

Options (applies to both methods above):

• --port: port number the server listens on
• --etcd-hosts: a comma separated list of etcd servers in the form of <address>:<port>
• --uri: the base directory key for the etcd configurations, default is /etcd_vhost/

Registering a new virtual host on etcd

Create a virtual host www.example.com that points to http://10.0.0.1:8080:

core@coreos01 ~ $ etcdctl set /etcd_vhost/vhosts/www.example.com/10.0.0.1:8080 "http://10.0.0.1:8080"
http://10.0.0.1:8080

Running tests

• make sure a local etcd endpoint localhost:4001 is accessible
• run npm test

TODO:

• health check and auto-remove unhealthy vhost targets
• separate presence daemon to add docker containers to vhost entries based on env variables
• support web sockets

Related Readings

• etcd
• etcd - Reading and Writing from Inside a Container