The Docker runner writes logs to stdout and stderr. You can access the logs using the web Dashboard or the docker command line utility.
$ docker logs <container name>
The Docker runner is configured to log runtime events. You can enable debug or trace level logs to get detailed information on the flow through the system.
You can enable http request logging to get detailed http communication details between the runner and the server. This generates significant output and should only be enabled to troubleshoot communication issues.