sysinfo should log tracebacks to a log file instead of printing them to the terminal

[Christopher Armstrong]

If a plugin raises an exception, a big traceback will be printed to the terminal. This should be avoided, and instead a log file should be written.

[Jamu Kakar (jkakar)]

I wonder if it would be worth including a note when failures occur:

 => landscape-sysinfo plugins failed. See /var/log/landscape/sysinfo.log.

[Christopher Armstrong (radix)]

Thanks for the idea.

It's ready for review in the attached branch.

[Thomas Herve (therve)]

[1] Flakes
landscape/sysinfo/sysinfo.py:4: 'maybeDeferred' imported but unused

Everything else looks good, it's fairly cool. The only problems I have is:
 * the log file can't be configured
 * the log file is created even if no errors are printed.

But nothing major, +1.

[Christopher Armstrong (radix)]

Ok, I made some changes.

Thomas: I've fixed your [1]

- Rotation is now size-based. It rotates at 500k and keeps 1 backup file.
- The file is now put into ~/.landscape/sysinfo.log.

[Andreas Hasenack (ahasenack)]

Hmm, one possible problem, which I'm not even sure was introduced in this branch, but that I just noticed. When there is an error of this kind, the exit status is not 1, but still one:

root@hardy-vm:~# chmod 0700 /proc
root@hardy-vm:~# su - andreas
andreas@hardy-vm:~$ landscape-sysinfo; echo $?
  Users logged-in: 1

  => Load plugin raised an exception. See ~/.landscape-sysinfo.log for information.
  => Disk plugin raised an exception. See ~/.landscape-sysinfo.log for information.
  => Memory plugin raised an exception. See ~/.landscape-sysinfo.log for information.
  => Processes plugin raised an exception. See ~/.landscape-sysinfo.log for information.
0
andreas@hardy-vm:~$

[Gustavo Niemeyer (niemeyer)]

Very very cool! Even WITH TESTS! +1!

[Gustavo Niemeyer (niemeyer)]

Oh, about the thing Andreas mentioned, it's an interesting point.

Maybe we should just log one line once for all plugins. The log file has details in any case.

[Christopher Armstrong (radix)]

Ok, I made it so there's only one note no matter how many plugins fail.

I also added word-wrapping to the note feature, since I noticed my note was >80 characters. Please check it out.

[Andreas Hasenack (ahasenack)]

I think the main issue is that it still exits with code 0 instead of something different when there is an error. And I just realized I made a typo in my previous comment: "... the exit statis is not 1, but still s/one/zero/". :)

[Thomas Herve (therve)]

Small conflict in landscape/sysinfo/deployment.py, everything else is fine, +1.

[Christopher Armstrong (radix)]

Thanks, merged

[Andreas Hasenack (ahasenack)]

This was released into production.