[systemd-devel] [RFC] split journal by loglevel

[Łukasz Stelmach]

It was <2013-10-28 pon 19:38>, when Lennart Poettering wrote:
> On Tue, 22.10.13 16:45, Łukasz Stelmach (l.stelmach at samsung.com) wrote:

[Adding Dariush Michaluk and Juho Son]

>> Hello Everyone.
>> 
>> <rant>
>> Some of you may know I and my colleagues work hard to make Tizen work
>> for you.
>> </rant>
>
> Rant? Hmm?

By definition[1] (n2 fits best IMHO ;)

>> Tizen is growing really fast and we've got a problem. A lot of code
>> produce a lot of messages. Some of them are more important than others.
>> We want to access debug (and info) messages when a system is working and
>> we don't want to keep them accross rebots. The obvious solution is to
>> split messages into two journal files based on log-level.  Less
>> important messages would be saved in /run/log/journal more important
>> ones in /var/log/journal.
>
> Sounds like a useful feature!
>
>> 
>> RFC.
>> 
>> As obvious as the desired result occurs I am not sure what is the best
>> place to hook and configure it. Is it another keyword (or set of
>> keywords) for SplitMode: level (level+uid, level+login (level+none?))?
>> Or maybe something around MaxLevelStore and line 836 of
>> journald-server.c[1]?
>
> I am tempted to suggest to add a new value to Storage=, maybe called
> "level" or so? And then add a new switch StoragePersistentLevel= which
> is only interpreted when Storage= equals "level" or if it equals "auto"
> and /var/log/journal actually exists. 

Looks reasonable.

>> There is yet another way I can think of: log everything to /run and
>> filter out everything below certain log-level. This solution however may
>> incur moments heavy load on systems during log rotation.
>> 
>> RFC.
>> 
>> Please give me some clues.
>
> We currently operate on the runtime journal only if the system journal
> is not open. If we keep both open we need to start working on both all
> the time. I figure this means a number of changes in journald-server.c,
> but most of them should be fairly straightforward...

We'll do.

Thank you.

[1]  http://www.dict.org/bin/Dict?Form=Dict1&Query=rant&Strategy=*&Database=wn&Submit=Submit%20query
-- 
Łukasz Stelmach
Samsung R&D Institute Poland
Samsung Electronics
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