HAProxy inside Docker: getting the logs


The official HAProxy docker image does not really offer an out-of-the-box way to get to HAProxy’s logs other than sending it to a remote log server. Sending log messages to stdout/stderr so you can view the logs with docker logs does not appear to be possible with HAProxy.

UPDATE for HAProxy 1.9 and newer

HAProxy has been updated to handle container environments better, see here.

HAProxy 1.8 and older

Exposing /dev/log on docker command line

To get access to the logs, without having to set up a service to receive them, you can choose to grant the container read-write access to the host’s /dev/log.

docker run -v /dev/log:/dev/log:rw haproxy

Then, make sure you set logging towards /dev/log in haproxy.cfg, like so:

  log /dev/log  local0
  log /dev/log  local1 notice

Exposing /dev/log in docker-compose YAML

In your docker-compose YAML, you can add the volume for /dev/log as follows:

    image: haproxy:alpine
      - /dev/log:/dev/log:rw

Accessing the logs

With the above examples, the HAProxy logs should now be available on your host machine, simply run journalctl -f there to see them pass by.

There is, of course, a probability that I missed a way to get to the logs other than sending them to a remote syslog service, but my droplet at Digital Ocean is only so large, and I intend to stay within my budget… Please let me know in the comments below if there is a better way to get to the logs.

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HAProxy: routing HTTP requests by domain name

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