Re: multiple log streams

[Joan Picanyol i Puig <lists-supervision@biaix.org>]

* Laurent Bercot <ska-supervision@skarnet.org> [20090903 23:33]:
> > Assuming producer & consumer are supervise/runsv managed services, how
> > do I reliably handle producer's log rotation?
> 
>  Why do you even use multilog/svlogd, since you have written your own
> logging facility ?
>  Make your consumer just read from stdin and log reliably to the
> multiple places you need; and have it run as a logger for the producer,
> in /service/producer/log/run. You won't have to deal with multilog/
> svlogd's rotation.

I have multiple consumers, some real-time and some batch. I need to be
able to easily adapt to more consumers appearing. Batch consumers are
handled at rotation time, real-time must feed from current. In case of >
1 real-time consumers, I should be able to get by with multitee.

> > My consumer opens /service/producer/log/main/current and gets signaled
> > by producer/log upon rotation. My consumer main loop yields every
> > iteration (say, by sleeping every 10ms), and its signal handler for log
> > rotation sets a global flag. When set, it reads until EOF on
> > log/main/current 's fd, closes it and reopens it. So far so good (please
> > correct me if I'm wrong). 
> 
>  Um, I don't quite get what you're doing, but it sounds like your consumer
> is performing active waiting.

I do usleep() every iteration, which does not count as active waiting in
my book. I'm not handling EINTR (I just keep reading until EOF &&
signaled).

> Don't: use a select()/poll()/iopause() loop
> listening on stdin, with a long - perhaps infinite - timeout.
>  If you need to trap signals, use the self-pipe trick.
>  http://www.skarnet.org/skalibs/selfpipe.html

Yep, that's definitely The Right Way.

tks
--
pica