Log rotation

[benjaoming]

Summary

After #4865 we have centralized the logging configuration and can start to use log rotation. This requires amending the docs because users might be instructed to just look at server.log and rotation might result in different file names.

Real-life consequences (anything community should be aware, for instance how it affects your deployment)

It's not too serious because currently the log file is cleared upon restart of ka lite, so the only implication is if you want to fetch a log for an error that occurred in a previous session.

[benjaoming]

One method to guarantee full logging for the daemon (which redirects ALL stderr and stdout to server.log) would be to keep the existing mechanism where server.log is just overwritten each time KA Lite is started.

Following that, we could start logging with RotatingFileHandler to ~/.kalite/log/server.log.

On top of that, we need to do a quick empirical trial to see that exceptions at various levels (module load and views) are caught in the log, as those are the most important ones.

[benjaoming]

This is implemented in #5449 and will be released in 0.17.1.

It doesn't contain any serious challenges, assuming that devices can easily carry 30 days of logs.

Unfortunately, maxBytes is not an accepted kwarg for TimedRotatingFileHandler, so we can't put an upper cap on the storage required for these logs. However, having 30 days back should not require substantial storage.

[benjaoming]

The timed log rotation will neatly place the date of the old log file when it rotates :)