Re: monitoring svlogd-produced logfiles

[Vincent Danen <vdanen@linsec.ca>]

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* Alex Efros <powerman@powerman.asdfGroup.com> [2006-06-15 02:59:09 +0300]:

> There a lot of ways to do what you need and I think you overcomplicate.

Very possible... =)

> If you don't need svlogd writing to disc and wish to redirect it output
> to some 'summarize' program, then why not use that program instead of
> svlogd in ./log/run? Main svlogd task is reliable _writing_to_disc_!

No, I do need svlogd to write to disk.  Well, maybe not.  I'm using
socklog for my logging so, for instance, I have /var/log/system/all
which has a config of "*.*".  I can duplicate that to something else,
but svlogd is handling all of the logging from socklog.  So I do need
svlogd to do it's thing (unless I setup another socklog service to read
/dev/log... can I have two socklog processes doing that?)

> But you can configure svlogd to duplicate your logs (optionally filtered)
> to STDERR (in addition to writing to disc). In degenerate case you even
> can configure svlogd to write nothing to disc and send all log lines to
> STDERR, but I don't understand why you need svlogd in this case. :)

No, I need svlogd to write the logs to disk.  In addition to the on-disk
logs, I want something to process those logs in realtime... to make a
summary log and something that I can have sitting open writing matched
entries to STDOUT so I can view it over ssh on my desktop... in
realtime.

> Then, in ./log/run you redirect svlogd's STDERR to some FIFO file:
>     svlogd /var/log/something 2>/var/log/MYFIFO
> (you can configure a lot of different svlogd to output into single FIFO)
> and setup special service which will fetch data from /var/log/MYFIFO,
> summarize it, print colored to /dev/tty12 or everything - ./run example:
>     exec my_cool_summarizer <>/var/log/MYFIFO

What does <> do?  I've never seen that notation before.

> Only one important note about FIFOs - if your 'my_cool_summarizer'
> service will be down and will not read from /var/log/MYFIFO all other
> svlogd which write into FIFO will also stop soon (after they fill kernel
> buffers) and in turn will stop services which they logging.

Right... if there's nothing to empty the buffer, it'll block svlogd.
That's fine... I can make sure, via dependency handling, that the
summarizing service is started first.

Some ideas... =)

BTW, I think I sent the response on the "tail -F" thing to you and not
the list... to summ, I did try "-n 0 -F" and it didn't follow.  Could be
a swatch thing tho... I'll have to try it again and see if it still
doesn't work.  If it doesn't, I still need to find an alternative to it,
so any suggestions are welcome.

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