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work::mod_perl-2.0.10:UsersContributed_Perl-Docum0::docs::api::Apache2::Log(3)

NAME
       Apache2::Log - Perl API for Apache Logging Methods

Synopsis
	 # in startup.pl
	 #--------------
	 use Apache2::Log;

	 use Apache2::Const -compile =>	qw(OK :log);
	 use APR::Const	   -compile => qw(:error SUCCESS);

	 my $s = Apache2::ServerUtil->server;

	 $s->log_error("server:	log_error");
	 $s->log_serror(__FILE__, __LINE__, Apache2::Const::LOG_ERR,
			APR::Const::SUCCESS, "log_serror logging at err	level");
	 $s->log_serror(Apache2::Log::LOG_MARK,	Apache2::Const::LOG_DEBUG,
			APR::Const::ENOTIME, "debug print");
	 Apache2::ServerRec->log_error("routine	warning");

	 Apache2::ServerRec::warn("routine warning");

	 # in a	handler
	 #-------------
	 package Foo;

	 use strict;
	 use warnings FATAL => 'all';

	 use Apache2::Log;

	 use Apache2::Const -compile =>	qw(OK :log);
	 use APR::Const	   -compile => qw(:error SUCCESS);

	 sub handler {
	     my	$r = shift;
	     $r->log_error("request: log_error");

	     my	$rlog =	$r->log;
	     for my $level qw(emerg alert crit error warn notice info debug) {
		 no strict 'refs';
		 $rlog->$level($package, "request: $level log level");
	     }

	     # can use server methods as well
	     my	$s = $r->server;
	     $s->log_error("server: log_error");

	     $r->log_rerror(Apache2::Log::LOG_MARK, Apache2::Const::LOG_DEBUG,
			    APR::Const::ENOTIME, "in debug");

	     $s->log_serror(Apache2::Log::LOG_MARK, Apache2::Const::LOG_INFO,
			    APR::Const::SUCCESS, "server info");

	     $s->log_serror(Apache2::Log::LOG_MARK, Apache2::Const::LOG_ERR,
			    APR::Const::ENOTIME, "fatal	error");

	     $r->log_reason("fatal error");
	     $r->warn('routine request warning');
	     $s->warn('routine server warning');

	     return Apache2::Const::OK;
	 }
	 1;

	 # in a	registry script
	 # httpd.conf: PerlOptions +GlobalRequest
	 use Apache2::ServerRec	qw(warn); # override warn locally
	 print "Content-type: text/plain\n\n";
	 warn "my warning";

Description
       "Apache2::Log" provides the Perl	API for	Apache logging methods.

       Depending on the	the current "LogLevel" setting,	only logging with the
       same log	level or higher	will be	loaded.	For example if the current
       "LogLevel" is set to warning, only messages with	log level of the level
       warning or higher (err, crit, elert and emerg) will be logged.
       Therefore this:

	 $r->log_rerror(Apache2::Log::LOG_MARK,	Apache2::Const::LOG_WARNING,
			APR::Const::ENOTIME, "warning!");

       will log	the message, but this one won't:

	 $r->log_rerror(Apache2::Log::LOG_MARK,	Apache2::Const::LOG_INFO,
			APR::Const::ENOTIME, "just an info");

       It will be logged only if the server log	level is set to	info or	debug.
       "LogLevel" is set in the	configuration file, but	can be changed using
       the "$s->loglevel()" method.

       The filename and	the line number	of the caller are logged only if
       "Apache2::Const::LOG_DEBUG" is used (because that's how Apache 2.0
       logging mechanism works).

       Note: On	Win32 Apache attempts to lock all writes to a file whenever
       it's opened for append (which is	the case with logging functions), as
       Unix has	this behavior built-in,	while Win32 does not. Therefore
       "Apache2::Log" functions	could be slower	than Perl's print()/warn().

Constants
       Log level constants can be compiled all at once:

	 use Apache2::Const -compile =>	qw(:log);

       or individually:

	 use Apache2::Const -compile =>	qw(LOG_DEBUG LOG_INFO);

   LogLevel Constants
       The following constants (sorted from the	most severe level to the least
       severe) are used	in logging methods to specify the log level at which
       the message should be logged:

       "Apache2::Const::LOG_EMERG"

       "Apache2::Const::LOG_ALERT"

       "Apache2::Const::LOG_CRIT"

       "Apache2::Const::LOG_ERR"

       "Apache2::Const::LOG_WARNING"

       "Apache2::Const::LOG_NOTICE"

       "Apache2::Const::LOG_INFO"

       "Apache2::Const::LOG_DEBUG"

   Other Constants
       Make sure to compile the	APR status constants before using them.	For
       example to compile "APR::Const::SUCCESS"	and all	the APR	error status
       constants do:

	 use APR::Const	   -compile => qw(:error SUCCESS);

       Here is the rest	of the logging related constants:

       "Apache2::Const::LOG_LEVELMASK"

       used to mask off	the level value, to make sure that the log level's
       value is	within the proper bits range. e.g.:

	 $loglevel &= LOG_LEVELMASK;

       "Apache2::Const::LOG_TOCLIENT"

       used to give content handlers the option	of including the error text in
       the "ErrorDocument" sent	back to	the client. When
       "Apache2::Const::LOG_TOCLIENT" is passed	to "log_rerror()" the error
       message will be saved in	the $r's notes table, keyed to the string
       "error-notes", if and only if the severity level	of the message is
       "Apache2::Const::LOG_WARNING" or	greater	and there are no other "error-
       notes" entry already set	in the request record's	notes table. Once the
       "error-notes" entry is set, it is up to the error handler to determine
       whether this text should	be sent	back to	the client.  For example:

	 use Apache2::Const -compile =>	qw(:log);
	 use APR::Const	   -compile => qw(ENOTIME);
	 $r->log_rerror(Apache2::Log::LOG_MARK,
			Apache2::Const::LOG_ERR|Apache2::Const::LOG_TOCLIENT,
			APR::Const::ENOTIME,
			"request log_rerror");

       now the log message can be retrieved via:

	 $r->notes->get("error-notes");

       Remember	that client-generated text streams sent	back to	the client
       MUST be escaped to prevent CSS attacks.

       "Apache2::Const::LOG_STARTUP"

       is useful for startup message where no timestamps, logging level	is
       wanted. For example:

	 use Apache2::Const -compile =>	qw(:log);
	 use APR::Const	   -compile => qw(SUCCESS);
	 $s->log_serror(Apache2::Log::LOG_MARK,
			Apache2::Const::LOG_INFO,
			APR::Const::SUCCESS,
			"This log message comes	with a header");

       will print:

	 [Wed May 14 16:47:09 2003] [info] This	log message comes with a header

       whereas,	when "Apache2::Const::LOG_STARTUP" is binary ORed as in:

	 use Apache2::Const -compile =>	qw(:log);
	 use APR::Const	   -compile => qw(SUCCESS);
	 $s->log_serror(Apache2::Log::LOG_MARK,
			Apache2::Const::LOG_INFO|Apache2::Const::LOG_STARTUP,
			APR::Const::SUCCESS,
			"This log message comes	with no	header");

       then the	logging	will be:

	 This log message comes	with no	header

Server Logging Methods
   "$s->log"
       get a log handle	which can be used to log messages of different levels.

	 my $slog = $s->log;

       obj: $s ( "Apache2::ServerRec object" )
       ret: $slog ( "Apache2::Log::Server" object )
	   "Apache2::Log::Server" object to be used with LogLevel methods.

       since: 2.0.00

   "$s->log_error"
       just logs the supplied message to error_log

	 $s->log_error(@message);

       obj: $s ( "Apache2::ServerRec object" )
       arg1: @message (	strings	ARRAY )
	   what	to log

       ret: no return value
       since: 2.0.00

       For example:

	 $s->log_error("running	low on memory");

   "$s->log_serror"
       This function provides a	fine control of	when the message is logged,
       gives an	access to built-in status codes.

	 $s->log_serror($file, $line, $level, $status, @message);

       obj: $s ( "Apache2::ServerRec object" )
       arg1: $file ( string )
	   The file in which this function is called

       arg2: $line ( number )
	   The line number on which this function is called

       arg3: $level ( "Apache2::LOG_* constant"	)
	   The level of	this error message

       arg4: $status ( "APR::Const status constant" )
	   The status code from	the last command (similar to $!	in perl),
	   usually "APR::Const constant" or coming from	an exception object.

       arg5: @message (	strings	ARRAY )
	   The log message(s)

       ret: no return value
       since: 2.0.00

       For example:

	 use Apache2::Const -compile =>	qw(:log);
	 use APR::Const	   -compile => qw(ENOTIME SUCCESS);
	 $s->log_serror(Apache2::Log::LOG_MARK,	Apache2::Const::LOG_ERR,
			APR::Const::SUCCESS, "log_serror logging at err	level");

	 $s->log_serror(Apache2::Log::LOG_MARK,	Apache2::Const::LOG_DEBUG,
			APR::Const::ENOTIME, "debug print");

   "$s->warn"
	 $s->warn(@warnings);

       is the same as:

	 $s->log_serror(Apache2::Log::LOG_MARK,	Apache2::Const::LOG_WARNING,
			APR::Const::SUCCESS, @warnings)

       obj: $s ( "Apache2::ServerRec object" )
       arg1: @warnings ( strings ARRAY )
	   array of warning strings

       ret: no return value
       since: 2.0.00

       For example:

	 $s->warn('routine server warning');

Request	Logging	Methods
   "$r->log"
       get a log handle	which can be used to log messages of different levels.

	 $rlog = $r->log;

       obj: $r ( "Apache2::RequestRec object" )
       ret: $rlog ( "Apache2::Log::Request" object )
	   "Apache2::Log::Request" object to be	used with LogLevel methods.

       since: 2.0.00

   "$r->log_error"
       just logs the supplied message (similar to "$s->log_error" ).

	 $r->log_error(@message);

       obj: $r ( "Apache2::RequestRec object" )
       arg1: @message (	strings	ARRAY )
	   what	to log

       ret: no return value
       since: 2.0.00

       For example:

	 $r->log_error("the request is about to	end");

   "$r->log_reason"
       This function provides a	convenient way to log errors in	a preformatted
       way:

	 $r->log_reason($message);
	 $r->log_reason($message, $filename);

       obj: $r ( "Apache2::RequestRec object" )
       arg1: $message (	string )
	   the message to log

       opt arg2: $filename ( string )
	   where to report the error as	coming from (e.g. "__FILE__")

       ret: no return value
       since: 2.0.00

       For example:

	 $r->log_reason("There is no enough data");

       will generate a log entry similar to the	following:

	 [Fri Sep 24 11:58:36 2004] [error] access to /someuri
	 failed	for 127.0.0.1, reason: There is	no enough data.

   "$r->log_rerror"
       This function provides a	fine control of	when the message is logged,
       gives an	access to built-in status codes.

	 $r->log_rerror($file, $line, $level, $status, @message);

       arguments are identical to "$s->log_serror".

       since: 2.0.00

       For example:

	 use Apache2::Const -compile =>	qw(:log);
	 use APR::Const	   -compile => qw(ENOTIME SUCCESS);
	 $r->log_rerror(Apache2::Log::LOG_MARK,	Apache2::Const::LOG_ERR,
			APR::Const::SUCCESS, "log_rerror logging at err	level");

	 $r->log_rerror(Apache2::Log::LOG_MARK,	Apache2::Const::LOG_DEBUG,
			APR::Const::ENOTIME, "debug print");

   "$r->warn"
	 $r->warn(@warnings);

       is the same as:

	 $r->log_rerror(Apache2::Log::LOG_MARK,	Apache2::Const::LOG_WARNING,
			APR::Const::SUCCESS, @warnings)

       obj: $r ( "Apache2::RequestRec object" )
       arg1: @warnings ( strings ARRAY )
	   array of warning strings

       ret: no return value
       since: 2.0.00

       For example:

	 $r->warn('routine server warning');

Other Logging Methods
   LogLevel Methods
       after getting the log handle with "$s->log" or "$r->log", use one of
       the following methods (corresponding to the "LogLevel" levels):

	 emerg(), alert(), crit(), error(), warn(), notice(), info(), debug()

       to control when messages	should be logged:

	 $s->log->emerg(@message);
	 $r->log->emerg(@message);

       obj: $slog ( server or request log handle )
       arg1: @message (	strings	ARRAY )
       ret: no return value
       since: 2.0.00

       For example if the "LogLevel" is	"error"	and the	following code is
       executed:

	 my $slog = $s->log;
	 $slog->debug("just ", "some debug info");
	 $slog->warn(@warnings);
	 $slog->crit("dying");

       only the	last command's logging will be performed. This is because
       warn, debug and other logging command which are listed right to error
       will be disabled.

   "alert"
       See LogLevel Methods.

   "crit"
       See LogLevel Methods.

   "debug"
       See LogLevel Methods.

   "emerg"
       See LogLevel Methods.

   "error"
       See LogLevel Methods.

   "info"
       See LogLevel Methods.

   "notice"
       See LogLevel Methods.

       Though Apache treats "notice()" calls as	special. The message is	always
       logged regardless the value of "ErrorLog", unless the error log is set
       to use syslog. (For details see httpd-2.0/server/log.c.)

   "warn"
       See LogLevel Methods.

General	Functions
   "LOG_MARK"
       Though looking like a constant, this is a function, which returns a
       list of two items: "(__FILE__, __LINE__)", i.e. the file	and the	line
       where the function was called from.

	 my ($file, $line) = Apache2::Log::LOG_MARK();

       ret1: $file ( string )
       ret2: $line ( number )
       since: 2.0.00

       It's mostly useful to be	passed as the first argument to	those logging
       methods,	expecting the filename and the line number as the first
       arguments (e.g.,	"$s->log_serror" and "$r->log_rerror" ).

Virtual	Hosts
       Code running from within	a virtual host needs to	be able	to log into
       its "ErrorLog" file, if different from the main log. Calling any	of the
       logging methods on the $r and $s	objects	will do	the logging correctly.

       If the core "warn()" is called, it'll be	always logged to the main log
       file. Here is how to make it log	into the vhost error_log file.	Let's
       say that	we start with the following code:

	 warn "the code	is smoking";

       1.  First, we need to use mod_perl's logging function, instead of
	   "CORE::warn"

	   Either replace "warn" with "Apache2::ServerRec::warn":

	     use Apache2::Log ();
	     Apache2::ServerRec::warn("the code	is smoking");

	   or import it	into your code:

	     use Apache2::ServerRec qw(warn); #	override warn locally
	     warn "the code is smoking";

	   or override "CORE::warn":

	     use Apache2::Log ();
	     *CORE::GLOBAL::warn = \&Apache2::ServerRec::warn;
	     warn "the code is smoking";

	   Avoid using the latter suggestion, since it'll affect all the code
	   running on the server, which	may break things. Of course you	can
	   localize that as well:

	     use Apache2::Log ();
	     local *CORE::GLOBAL::warn = \&Apache2::ServerRec::warn;
	     warn "the code is smoking";

	   Chances are that you	need to	make the internal Perl warnings	go
	   into	the vhost's error_log file as well. Here is how	to do that:

	     use Apache2::Log ();
	     local $SIG{__WARN__} = \&Apache2::ServerRec::warn;
	     eval q[my $x = "aaa" + 1;]; # this	issues a warning

	   Notice that it'll override any previous setting you may have	had,
	   disabling modules like "CGI::Carp" which also use $SIG{__WARN__}

       2.  Next	we need	to figure out how to get hold of the vhost's server
	   object.

	   Inside HTTP request handlers	this is	possible via
	   "Apache2->request".	Which requires either "PerlOptions
	   +GlobalRequest" setting or can be also done at runtime if $r	is
	   available:

	     use Apache2::RequestUtil ();
	     sub handler {
		 my $r = shift;
		 Apache2::RequestUtil->request($r);
		 ...

	   Outside HTTP	handlers at the	moment it is not possible, to get hold
	   of the vhost's error_log file. This shouldn't be a problem for the
	   code	that runs only under mod_perl, since the always	available $s
	   object can invoke a plethora	of methods supplied by "Apache2::Log".
	   This	is only	a problem for modules, which are supposed to run
	   outside mod_perl as well.

	   META: To solve this we think	to introduce 'PerlOptions
	   +GlobalServer', a big brother for 'PerlOptions +GlobalRequest',
	   which will be set in	modperl_hook_pre_connection.

Unsupported API
       "Apache2::Log" also provides auto-generated Perl	interface for a	few
       other methods which aren't tested at the	moment and therefore their API
       is a subject to change. These methods will be finalized later as	a need
       arises. If you want to rely on any of the following methods please
       contact the the mod_perl	development mailing list so we can help	each
       other take the steps necessary to shift the method to an	officially
       supported API.

   "log_pid"
       META: what is this method good for? it just calls getpid	and logs it.
       In any case it has nothing to do	with the logging API. And it uses
       static variables, it probably shouldn't be in the Apache	public API.

       Log the current pid

	 Apache2::Log::log_pid($pool, $fname);

       obj: $p ( "APR::Pool object" )
	   The pool to use for logging

       arg1: $fname ( file path	)
	   The name of the file	to log to

       ret: no return value
       since: subject to change

See Also
       mod_perl	2.0 documentation.

Copyright
       mod_perl	2.0 and	its core modules are copyrighted under The Apache
       Software	License, Version 2.0.

Authors
       The mod_perl development	team and numerous contributors.

perl v5.24.1		     work::mod_perl-2.0.10::docs::api::Apache2::Log(3)

NAME | Synopsis | Description | Constants | Server Logging Methods | Request Logging Methods | Other Logging Methods | General Functions | Virtual Hosts | Unsupported API | See Also | Copyright | Authors

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