Re: [users@httpd] Prefork MPM: Locking of error logs during write?
On Sun, Sep 7, 2014 at 4:30 PM, Jeff Trawick wrote: > > Apache httpd on Unix doesn't use locking. The file is opened in the > parent with O_APPEND. > > If the writers inherit that descriptor, all is okay for "small" buffers; > if a writer opens without O_APPEND, bad. > Thanks Jeff, In my tests over the last few days it's clear that buffer is about 4K (On CentOS, anyway). I wrote tens of gigs of logs using 50 processes and never say any intermixing of the logs at all with the message < 4K. With a larger log message it was easy to trigger the mixing of logs. Thanks for the information and confirmation. -- Bill Moseley mose...@hank.org
Re: [users@httpd] Prefork MPM: Locking of error logs during write?
On Sat, Sep 6, 2014 at 10:31 AM, Bill Moseley wrote: > Apache 2.2.15 on Linux. > > When Apache children send output to stderr it ends up in my error_log file. > > Does Apache have any mechanism to prevent intermixing of this output? > That is, if all Apache children write large ( but < 4k) strings to stderr > does Apache have anything to prevent inter mixing of the output? > > Apache doesn't do any locking or use semaphores to prevent concurrent > writing to the log, correct? > > > -- > Bill Moseley > mose...@hank.org > Apache httpd on Unix doesn't use locking. The file is opened in the parent with O_APPEND. If the writers inherit that descriptor, all is okay for "small" buffers; if a writer opens without O_APPEND, bad. -- Born in Roswell... married an alien... http://emptyhammock.com/
[users@httpd] Prefork MPM: Locking of error logs during write?
Apache 2.2.15 on Linux. When Apache children send output to stderr it ends up in my error_log file. Does Apache have any mechanism to prevent intermixing of this output? That is, if all Apache children write large ( but < 4k) strings to stderr does Apache have anything to prevent inter mixing of the output? Apache doesn't do any locking or use semaphores to prevent concurrent writing to the log, correct? -- Bill Moseley mose...@hank.org