This container updates an HAProxy config template periodically using the results of DNS resolution to trigger the update and apply the template and reload HAProxy.
You can either run this container directly by mounting a template file at /etc/haproxy.cfg.tpl
or by copying and baking the template file in using a new Dockerfile. Either way it requires
an environment variable SERVICE_HOSTNAME which is the DNS name to resolve when updating the template.
Multiple DNS hostnames may be specified separated by commas.
HAProxy 1.9+ supports direct to stdout/stderr logging so rsyslog was removed.
This container runs as root rather than haproxy as it must write over the config file while running.
Run the image directly by mounting the config file as a volume:
$ docker run \
-e SERVICE_HOSTNAME=tasks.galera \
-e UPDATE_FREQUENCY=10 \
-v /path/to/your/haproxy.cfg.tpl:/etc/haproxy.cfg.tpl:ro \
colinmollenhour/haproxy-service:2.6-alpine
Or build the config into the image:
FROM colinmollenhour/haproxy-service:2.6-alpine
COPY haproxy.cfg.tpl /etc/haproxy.cfg.tpl
ENV SERVICE_HOSTNAME my-service
ENV UPDATE_FREQUENCY 5
See the samples/ directory for basic examples.
Any block of text between the markers {{HOSTS}} and {{/HOSTS}} (must be on separate lines) will be rendered
in-place for each IP resolved by the SERVICE_HOSTNAME. The variables $ip and $num (the last octet of the $ip)
will be replaced accordingly. The IP addresses will always be sorted in the same order.
There may be multiple {{HOSTS}} ... {{/HOSTS}} blocks in the same template file.
Example:
default-server inter 1s
{{HOSTS}}
server node${num} ${ip}:3306 check
{{/HOSTS}}
If the SERVICE_HOSTNAME resolves to 10.0.0.12 and 10.0.0.20 it would render:
default-server inter 1s
server node12 10.0.0.12:3306 check
server node20 10.0.0.20:3306 check
If you need to run some basic scripts on init before the first template render mount or add a file at
/docker-entrypoint-init.sh which will be sourced by docker-entrypoint.sh once on startup.