Hi,
Am Mittwoch, 27. Juli 2016 22:44:38 CEST schrieb Mark Gaiser:
On Tue, Jul 26, 2016 at 3:09 PM, Mark Gaiser <mark...@gmail.com> wrote:
On Tue, Jul 26, 2016 at 2:03 PM, Sebastian Kügler <se...@kde.org> wrote:
Hey,
[Please keep both lists addressed.]
Debugging multiscreen issues is a nightmare:
- there are at least 4 different processes involved (kded, kcmshell /
systemsettings, kscreen_backend_launcher and plasmashell)
- some are critical during log in
- they IPC with each other
- especially the backend launcher's debug is really hard to get at
This means that:
- it's hard (almost impossible) for users to get us good and useful logs
- it's hard for ourselves to debug and find out what's exactly going on,
especially when multiple components need to play in tune
Yesternight, after debugging the so-many-th issue, it occurred to me that
we
need to make this way easier to debug. Q(C)Debug falls short in that we
get
logs of individual components, if we're lucky. If we're really lucky, we
get
timestamps, so we can get a rough idea of what is going down when.
All of these problems can be solved with a relatively simple, shared log
file.
So I'd like to switch most of (lib)kscreen's debug output to logging to a
file. The files has then logs from multiple processes and will be much
easier
to go through.
API-wise, my main thing is having log messages and a bit of context, so
it'd
look like this:
Log::instance()->setContext("handling resume event");
// ...
Log::log("Enabled output" + output->name());
In the log, we'd then get
[TIMESTAMP] (kded: handling resume event) Enabled output eDP-1
The key here is that we get a mostly correct sequence of things, that all
the
info is there right away, and that it's easier for the user to annotate
the
log ("Now plugging in my external display as HDMI-2").
The file is simple enough that even plasmashell could log to the file (at
least until we've fixed the interaction between screen handling and
plasmashell), so we get the full picture.
libkscreen[sebas/log] has a basic implementation. It's incomplete in the
sense
that it needs a bit of autotesting (just haven't gotten to it yet),
review and
then switching over the code-base. (For now it's on by
default, but can be
disabled using a env var.)
I hope that this makes it much more straight-forward for us (and even
users)
to figure out where their multiscreen headaches are coming from, and that
it
gives us a one-stop shop (pretty much) to tell users what info we need to
fix
their bugs. ("Just send me the logfile in ~/.local/share/kscreen.log").
What do you think? If you like the idea, I'll polish up my
branch and will
post it for review, so we can discuss the actual implementation.
Cheers,
--
sebas
http://www.kde.org | http://vizZzion.org
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Hi,
Just a quick idea that might help you.
I'm not sure if the logging of those applications is already visible in
journalctl, but if it is then you can do something like this:
journalctl -u <unit> -u <another unit> -u <third one> -u <etc...> -f
-u would be the "units". Like plasmashell i guess.
-f means following the log (new entries appear on your screen).
Lastly, i would suggest to use a second pc independent of the one that
you're debugging. On that second machine just ssh into the one you're
debugging and execute the logging command from above.
This all obviously only works if you everything is already visible in
journalctl.
Good luck!
I hope this makes logging and debugging easier for you.
Cheers,
Mark
This idea was not an option?
It seems - to me, but i'm biased since i proposed it.. - like an idea with
minimal effort and probably gets the job done, no?
I think the problem with this approach is, that most (or even all?) of
these processes aren't units but simple processes.
A better approach using the power of journald would be something like:
journalctl -b --user _COMM=plasmashell + _COMM=kded5 QT_CATEGORY=kscreen +
_COMM=systemsettings5 + _COMM=kscreen_backend
which filters all logs based on the executable names, the current user
and the current boot. We can also search for specific qt logging categories
(e.g. we're searching for all kded5 logs in category "kscreen").
See "man 1 journalctl" and "man 7 systemd.journal-fields" for more
information.
I think this is a simple and powerful solution, which doesn't require more
code,
and doesn't have the race condition problems mentioned in the review
request
for the new code.
Cheers,
David
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