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Re: Merged lines with Apache::LogFile-based log handler

by derby (Abbot)
on Jul 09, 2007 at 19:18 UTC ( #625691=note: print w/ replies, xml ) Need Help??


in reply to Merged lines with Apache::LogFile-based log handler

Normally writes (of this size) are atomic so I doubt you need any type of locking mechanism. Looking at the XS code for Apache::LogFile, I see it does mutiple writes - for the message(s) and for the newline if the message(s) does not contain a newline:

int print(self, ...) Apache::LogFile self ALIAS: Apache::LogFile::PRINT = 1 PREINIT: int i; STRLEN len; char *str; CODE: for(i=1; i<items; i++) { str = SvPV(ST(i),len); RETVAL += write(self->log_fd, str, len); } if(*(SvEND(ST(i-1)) - 1) != '\n') RETVAL += write(self->log_fd, "\n", 1); OUTPUT: RETVAL
Under heavy load, what you're seeing is one process being put into a wait state before the newline is output. You don't mention it, but did your logfile also contain blank lines? It should've.

Since you have control, if you append a newline to $message in your _logger method before you print, your logs should come out fine under heavy load.

my $message = qq{$now [$pid] X-Loadbalancer: $lb_value ($status)\n} ; print Tiscali::LoadBalancerLogFile $message ;

-derby


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Re^2: Merged lines with Apache::LogFile-based log handler
by bronto (Priest) on Jul 10, 2007 at 11:26 UTC

    Hello derby

    First things first: it worked! Thanks a lot

    Second: a small change in apache's configuration is needed: I erroneously configured my module as a Fixup handler, which caused it to be called a huge number of times per line, that amplified the problem. Configuring it as a log handler correctly writes one line at a time. Anyway, I also tested it with the wrong apache configuration, and it still worked, so your solution is absolutely right.

    Under heavy load, what you're seeing is one process being put into a wait state before the newline is output. You don't mention it, but did your logfile also contain blank lines? It should've.

    Right. I didn't mention it since I pasted an example that contained a blank line. Nevertheless, it was not completely evident. My fault.

    Big thanks!!!

    Ciao!
    --bronto


    In theory, there is no difference between theory and practice. In practice, there is.

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