Get logjam logging working again

[oubiwann]

Though the logjam app gets started by YAWS, nothing is logged to the console. Need to find out why. Questions:

• is the configuration defined in lfe.config getting loaded?
• is it being properly read?
• when YAWS starts, what's its cwd? (should be the Docker WORKDIR ...)
• does logjam standalone still work?

[oubiwann]

Confirmed an issue regarding that last bullet:

• Logjam no longer logs ... lfex/logjam#8

[oubiwann]

Based on the latest comments in the logjam ticket, it seems that we might have a quickfix by starting lager explicitly in the YAWS config ...

[oubiwann]

That didn't work, mostly because lager has to start first, before logjam, and I can't seem to figure out how to enforce order using multiple runmod declarations in the yaws config.

However, what did work, was setting the --erlarg '-s lager' flag when starting YAWS (after the -pa and before the --conf). So, logging is working(ish) again ... what's missing though is the ANSI colors and the specific format defined by logjam. That's being debugged in the linked ticket (see above).

[oubiwann]

So it seems that for Erlang 17.5, 18.3, 19.3, and 20.3, logging works with logjam when using lager 2.x. With Erlang 21.3 and 22.0, lager 2.x is broken, or at least the way that logjam is using it is.

[oubiwann]

Updated the description with checkboxes. Basically, the solution here is manifold:

• Erlang <= 20.3, use the current logjam
• Erlang > 20.3, use the future version of logjam that supports the new Erlang logger module (see Support Erlang logger module lfex/logjam#10)