colinmollenhour/haproxy-service repository overview

⁠Tags

• 2.6-alpine - Based on haproxy:2.6-alpine
• 1.8-alpine, latest - Based on haproxy:1.8-alpine, not maintained

⁠HAProxy Service Load Balancer

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.

⁠Usage

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.

⁠Logging

HAProxy 1.9+ supports direct to stdout/stderr logging so rsyslog was removed.

⁠User

This container runs as root rather than haproxy as it must write over the config file while running.

⁠Usage

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 in the github repo for basic examples.

⁠Template Format

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

⁠Init Scripts

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.