Enable log rotating

[erkyrath]

I see that when you do docker-compose up --build, log info goes to stdout. This should go to /var/log/unbox/unbox.log.

Then we'd have to set up logrotate. Except I don't know exactly how to do that. For Apache, logrotate is configured to do "/etc/init.d/apache2 reload" after rotation so that the server closes and reopens its logging file handle. What is the equivalent here?

[curiousdannii]

Docker has various logging options: https://docs.docker.com/config/containers/logging/

But I did see that the default is some JSON system, and it doesn't support any log rotating. So yes, this is important. I know nothing about it though.

FYI, the command to start it in the background is docker-compose up --build -d.

[erkyrath]

The suggested plan seems to be "log-driver": "local" , which shoves the logs into an opaque file with automatic rotation. Then you use the docker logs command to examine them.

docker info indicates that the current log-driver is the (default) "json-file", and docker logs does in fact work. But I have no idea where those json files are. Inside each container, I suppose.

[erkyrath]

The logs now use log-driver:local, but we observe that bringing the containers down and back up wipes the logs. This is not ideal.

Digging around, I found the comment:

You can persist all container log files by creating a volume mount point to the Docker host machine or central log server.

This is still on the todo list.

[erkyrath]

I looked further into this and it's not as obvious as the comment above implies.

The current logs are not kept inside the container. They're in a container-specific folder on the host. (/var/lib/docker/containers/$ID/local-logs) So that's why they disappear when the container goes down. I did not find a way to change this.

There's a lot of blog discussion about centralizing your log files but they seem to boil down to three plans:

• Have your app write logs to a location inside the container (rather than printing to stdout and letting docker capture that).
• Use a different log driver such as journald. Then set that up on the host.
• Use my awesome log-capturing product (written by the author of this blog post).

None of these sounds simple, unless you know more about journald than me.