Posts in category monitor

Daemon monitor and live status

Recently I added 2 new functionnalities to the Licorn® daemon and the CLI interface. The first is a simple extension of the existing get status. There is now a -m CLI switch, which implies that the CLI process stays connected to the daemon, and updates the status on the terminal. The refresh delay and various parameters (fixed refresh count / maximum refresh time / clear screen between outputs) are configurable via other cli switches; see get status --help for details. Just remember this command: 

get status -m

Default parameters are cool anyway (refresh time: 1 second, clear screen: yes, refresh count: infinite, max. refresh time: infinite). Just hit Control-C to stop the status updates when you're done.

The second functionnality could be seen as an internal sniffer, in the daemon. It's called monitor mode. With a new CLI command (get events, not to name it), you can access any internal event, decision or message generated in the daemon. This monitor mode will eventually supersede the LTRACE facility, but it's not very clear at this point because the monitor could impact the daemon performance much more than LTRACE (it's always compiled in, whereas LTRACE is usable only when the Python interpreter is in debug mode).

You use the monitor mode like you use LTRACE (levels are the same for both). E.g. to display std (standard) events: 

get events

Or to dump only the inotifier related events: 

get events -f inotifier

You can combine them to your liking, just the same you would do with LTRACE: 

get events -f 'core^system|daemon^threads'

The bonus is the full sniffing mode: just add 'logging' to the facilities you want to follow, and every output message sent by the daemon to any other CLI command (run by you or by others) will be pushed to your local monitor session: 

get events -f 'core|logging'

The bonus: you can even monitor a remote daemon from your local machine. Just set the special environment variable before launching the command: 

export LICORN_SERVER='IP_or_hostname'
get events

And you're done! Happy monitoring, and remember: these things can easily flood your terminal!

NOTE: currently, only inotifier and logging are fully converted to monitor mode. Other parts will soon follow. The rest of the code still uses the LTRACE facility.