Provided by: libapache2-mod-perl2_2.0.10-2ubuntu3.18.04.1_amd64 
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 v5.26.1 libapache2-mod-perl2-2.0.10::docs::api::Apache2::Log(3pm)