haproxy + ucarp
This image runs a haproxy with ucarp to make it highly available.
This image uses host networking, which requires Docker >= 0.11.
To configure haproxy, you can either bind-mount a haproxy.cfg from your
host system to
/haproxy/haproxy.cfg in the container or create a custom
image by using a Dockerfile like this:
FROM fish/haproxy-docker ADD haproxy.cfg /haproxy/haproxy.cfg
If you need graceful reloads and can't affort rebuilding and restarting
haproxy completely, you can bind-mount a config from your host and use
docker kill -s HUP ... to reload the config.
Start a container like this on two hosts:
$ docker run --cap-add=NET_ADMIN --net host fish/haproxy-docker 10.0.1.201 foobar23 wlan0
Now you should have two haproxy running and ucarp running on the given interface, making sure only one listens on 10.0.1.201.
You can set the IPS env var to bind additional IPs on the active system.
If you're using IP based vhosts, you need to set
net.ipv4.ip_nonlocal_bind=1 to allow the slave haproxy to bind to the
right addresses even if they are not configured on your interfaces.
If any service haproxy goes down, the container is supposed to kill UCARP so the IP gets removed and the backup can take over.
If for any reasons this isn't working, kill the container manually. This should cause the backup to take over.
If this is not the case, there is a problem with the backup container. You might want to restart it.