Apache2::ModLogConfig - a Perl interface to mod_log_config
Call a Perl handler from a CustomLog format specification:
CustomLog
<Perl> use Apache2::ModLogConfig (); sub My::Format { my ($r)=@_; return $a_string; } </Perl> CustomLog LOGFILE "... %{My::Format}^..."
Use a Perl handler as logfile:
PerlModule Apache2::ModLogConfig PerlModule My::LogReceiver CustomLog "@perl: My::LogReceiver" "format spec"
Print to a logfile:
use Apache2::ModLogConfig (); sub handler { my ($r)=@_; ... my $log=$r->server->custom_log_by_name('logs/access_log'); my $success=$log->print($r, qw/тут был вася/, "\n"); ... }
The reason to start this module was to monitor the number of incoming and outgoing bytes for each request. mod_log_config in combination with mod_logio can log these numbers. But in Perl they are really hard to get.
mod_log_config
mod_logio
mod_logio uses a network-level input filter as byte counter. The outgoing bytes are counted by the core output filter and reported back to mod_logio if loaded.
Now, with the help of this module you can do 3 things:
call a Perl handler from a CustomLog format specification
use a Perl handler in place of a logfile
write out-of-bound messages to logfiles managed by mod_log_config
For this to work, the module must be loaded before the PerlOpenLogsHandler phase. Calling a Perl handler from a format specification requires an early start of the interpreter and the module must be loaded at that stage. That means you need either a <Perl>...</Perl> section in your httpd.conf or the module must be loaded by PerlLoadModule.
PerlOpenLogsHandler
<Perl>...</Perl>
PerlLoadModule
Note, while developing this module I have found a bug in httpd that can lead to segfaults. It is present at least up to httpd 2.2.17. It occurs if mod_log_config is statically compiled into httpd and BufferedLogs are used. In this case avoid changing the BufferedLogs setting while restarting httpd via SIGHUP or SIGUSR1.
BufferedLogs
SIGHUP
SIGUSR1
See https://issues.apache.org/bugzilla/show_bug.cgi?id=50861
To be used this way Apache2::ModLogConfig registers the ^ format with mod_log_config.
Apache2::ModLogConfig
^
^ was chosen because it resembles the ^ in a number of Perl variables like $^V for example.
$^V
Now, a format specifier can receive an argument. The argument is given in braces between the % sign and the specifier. The ^ specifier's argument specifies the Perl handler to call. A fully qualified name is expected.
%
Example:
LogFormat "%{My::Handler::function}^" perllog
The handler is called with an Apache2::RequestRec object as the only parameter. In a chain of internal redirects this is by default the final request. It can be modified according to the mod_log_config documentation:
LogFormat "%<{My::Handler::function}^" perllog
This way the initial request is passed to the handler.
Other modifiers are also applicable as described by mod_log_config.
Now Perl handler works as log drain. That means it will receive a log file.
CustomLog "@perl: My::LogReceiver" FORMATSPEC
The prefix @perl: is used to distinguish between a normal file name or pipe specification and the Perl handler.
@perl:
The actual handler name is resolved the usual modperl way. That means if there is no function named My::LogReceiver, My::LogReceiver::handler is looked up. Auto-loading should work as well (although untested). Further, an anonymous function can be specified as:
My::LogReceiver
My::LogReceiver::handler
CustomLog "@perl: sub { my ($r, @strings)=@_; ... }" FORMATSPEC
The handler is called with the final request of a chain of internal redirects as the first parameters. The other parameters are all strings where each one corresponds to either a the result of a format specifier or a constant string.
Assuming the following format specification
"input bytes=%I, output bytes=%O"
the handler is called with 6 parameters:
the request object
the string input bytes=
input bytes=
a number according to %I
%I
the string , output bytes=
, output bytes=
a number according to %O
%O
and a trailing \n to close the line
\n
Note, a possible PerlLogHandler runs before the mod_log_config handler. So, it's not possible to record a few values here and use them in a PerlLogHandler. A PerlCleanupHandler or a request pool cleanup handler however should be fine.
PerlLogHandler
PerlCleanupHandler
My original problem now can be solved as:
package My::IO; sub handler { my ($r, $in, $out)=@_; $r->notes->{InBytes}=$in; $r->notes->{OutBytes}=$out; } sub cleanup { my ($r)=@_; my ($in, $out)=@{$r->notes}{qw/InBytes OutBytes/}; ... }
in httpd.conf:
CustomLog "@perl: My::IO" "%I%O" PerlCleanupHandler My::IO::cleanup
Have you ever wanted to write to the access_log directly? I haven't. But now it's feasible and perhaps someone finds a weird usage case.
Apache2::ModLogConfig implements the following methods.
Assuming $s is a Apache2::ServerRec object this method returns the logfile names defined for this VHost. The elements of @names are literally the strings specified as first parameter to CustomLog.
$s
@names
Assuming $s is a Apache2::ServerRec object this method returns an Apache2::ModLogConfig object for the given name.
Assuming $log is an Apache2::ModLogConfig object and $r is an Apache2::RequestRec this method prints the strings in @strings to the file. No escaping is done.
$log
$r
@strings
$status is an APR status code (APR::Const::SUCCESS if all is well).
$status
APR::Const::SUCCESS
None.
modperl, mod_log_config, apache httpd
Torsten Förtsch, <torsten.foertsch@gmx.net>
Copyright (C) 2011 by Torsten Förtsch
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.12.3 or, at your option, any later version of Perl 5 you may have available.
To install Apache2::ModLogConfig, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Apache2::ModLogConfig
CPAN shell
perl -MCPAN -e shell install Apache2::ModLogConfig
For more information on module installation, please visit the detailed CPAN module installation guide.