Add heartbeat file

[code-asher]

Fixes #1050.

@antofthy this will touch ~/.local/share/code-server/heartbeat (or wherever the user data directory is located) once a minute as long as there is an active browser connection. No need to review the code (although I would welcome it if you feel like it) but I'm pinging you to verify this'll work out for your use case.

[antofthy]

That would be perfect. Look forward to seeing this on the next code-server release.

[antofthy]

Confirmed heartbeat working as expected in the last release v2.1655-vsc1.39.2

[shivanik6z]

currently, if I deploy code-server for the first time, till the time I don't open it heartbeat shows a very old time. Is it intended? shouldn't heartbeat time be the creation time?

[antofthy]

Until it is updated heartbeat should either not exist or remain whatever it had been until then.

It is important that any monitoring also look at some other indicator that the user has only just started code-server, and perhaps has not opened there browser to connect to code-server. In my own case we have another file that gets updated whenever the user starts up.

I also now have a log monitor that also updates that secondary file with date/time of last logged web activity for the users 'environment'. This is different as code-server holds many of its web connections open. As such code-server activity does NOT always mean new web-activity, that a proxy 'ingress' service can log, though code-server updated its heartbeat while such a connection is open. Heartbeat is very important to monitor use of code-server!

NOTE Heartbeat is not strictly 'idle time', only a indication the user has code-server open on there browser. Other software (Jupyter for example) does not report connections, only real idleness, which can cause users to become disconnected if they don't do anything substantial in there browser.