robtuley / httprouter

Reverse proxy in Go; route discovery from etcd

Host-based HTTP Request Router Configured via Etcd

Configuring the Router

The following command line arguments are available:

-- logfile <filepath>  log to specified file
-- logurl <url>        POST log in batches to specified URL (e.g. Loggly bulk input)
-- etcdurl <url>       etcd URL, defaults to http://127.0.0.1:4001
-- etcdkey <key>       etcd key to discover routes from, defaults to /domains

If no alternative log file/url is specified, the application will log to stdout. All logs are in JSON format.

Discovery

Routes are discovered from etcd from its http API via the etcdwatch package. To add the internal URL http://internal.host:8000 for the demo.example.com:

etcdctl set /domains/demo.example.com/myRouteName http://internal.host:8000

The application will respect any routes in keys /domains/<domain.name>/<route.name> which contain routable internal URLs.

Proxy

HTTP requests are reverse proxied to any available domain routes via the Host header. If multiple routes are available, requests are round robin load balanced betwen them. If no route is available for a domain a 503 request will be served.

Example Discovery Script

An example discovery bash script to perform a basic polling discovery of a health check URL and poppulation of the route into etcd is:

#!/bin/sh
if [ "$#" -ne 3 ]; then
  echo "Usage: $0 <domain> <ip> <port>" >&2
  exit 1
fi

domain=$1
ip=$2
port=$3
printf "domain:> %s ip:> %s port:> %s" $domain $ip $port

while true; do
  curl -s --max-time 4 --connect-timeout 1 -A discovery-health-check -f http://$ip:$port/health-check > /dev/null
  if [ $? -eq 0 ]; then
    etcdctl set /domains/$domain/$ip:$port http://$ip:$port --ttl 10
    printf "ok:> %s at %s" $domain $ip:$port
  else
    etcdctl rm /domains/$domain/$ip:$port
    printf "error:> %s at %s" $domain $ip:$port
  fi
  sleep 5
done