=head1 NAME

Apache::Log - Perl API for Apache Logging Methods




=head1 Synopsis

  #in startup.pl
  #-------------
  use Apache::Log;
  
  use Apache::Const -compile => qw(OK :log);
  use APR::Const    -compile => qw(:error SUCCESS);
  
  my $s = Apache->server;
  
  $s->log_error("server: log_error");
  $s->log_serror(__FILE__, __LINE__, Apache::LOG_ERR,
                 APR::SUCCESS, "log_serror logging at err level");
  $s->log_serror(Apache::Log::LOG_MARK, Apache::LOG_DEBUG,
                 APR::ENOTIME, "debug print");
  Apache::Server->log_error("routine warning");
  
  Apache->warn("routine warning");
  Apache::warn("routine warning");
  Apache::Server->warn("routine warning");

  #in a handler
  #------------
  package Foo;
  
  use strict;
  use warnings FATAL => 'all';
  
  use Apache::Log;
  
  use Apache::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(Apache::Log::LOG_MARK, Apache::LOG_DEBUG,
                     APR::ENOTIME, "in debug");
  
      $s->log_serror(Apache::Log::LOG_MARK, Apache::LOG_INFO,
                     APR::SUCESS, "server info");
  
      $s->log_serror(Apache::Log::LOG_MARK, Apache::LOG_ERR,
                     APR::ENOTIME, "fatal error");

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

      return Apache::OK;
  }
  1;



=head1 Description

C<Apache::Log> provides the Perl API for Apache logging methods.

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

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

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

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

It will be logged only if the server log level is set to I<info> or
I<debug>. C<LogLevel> is set in the configuration file, but can be
changed using the
C<L<$s-E<gt>loglevel()|docs::2.0::api::Apache::Server/C_loglevel_>>
method.

The filename and the line number of the caller are logged only if
C<Apache::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
C<Apache::Log> functions could be slower than Perl's print()/warn().





=head1 Constants

Log level constants can be compiled all at once:

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

or individually:

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




=head2 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:

=head3 C<Apache::LOG_EMERG>

=head3 C<Apache::LOG_ALERT>

=head3 C<Apache::LOG_CRIT>

=head3 C<Apache::LOG_ERR>

=head3 C<Apache::LOG_WARNING>

=head3 C<Apache::LOG_NOTICE>

=head3 C<Apache::LOG_INFO>

=head3 C<Apache::LOG_DEBUG>



=head2 Other Constants


Make sure to compile the APR status constants before using them. For
example to compile C<APR::SUCESS> and all the APR error status
constants do:

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

Here is the rest of the logging related constants:


=head3 C<Apache::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;





=head3 C<Apache::LOG_TOCLIENT>

used to give content handlers the option of including the error text
in the C<ErrorDocument> sent back to the client. When
C<Apache::LOG_TOCLIENT> is passed to C<log_rerror()> the error message
will be saved in the C<$r>'s notes table, keyed to the string
I<"error-notes">, if and only if the severity level of the message is
C<Apache::LOG_WARNING> or greater and there are no other
I<"error-notes"> entry already set in the request record's notes
table. Once the I<"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 Apache::Const -compile => qw(:log);
  use APR::Const    -compile => qw(ENOTIME);
  $r->log_rerror(Apache::Log::LOG_MARK,
                 Apache::LOG_ERR|Apache::LOG_TOCLIENT,
                 APR::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
B<MUST> be escaped to prevent CSS attacks.





=head3 C<Apache::LOG_STARTUP>

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

  use Apache::Const -compile => qw(:log);
  use APR::Const    -compile => qw(SUCCESS);
  $s->log_serror(Apache::Log::LOG_MARK,
                 Apache::LOG_INFO,
                 APR::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 C<Apache::LOG_STARTUP> is binary ORed as in:

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

then the logging will be:

  This log message comes with no header




=head1 Server Logging Methods



=head2 C<$s-E<gt>log_error>

just logs the supplied message to I<error_log>

  $s->log_error(@message);

=over 4

=item obj: C<$s>
( C<L<Apache::ServerRec object|docs::2.0::api::Apache::ServerRec>> )

=item arg1: C<@message> ( strings ARRAY )

what to log

=item ret: no return value

=item since: 1.99_12

=back

For example:

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





=head2 C<$s-E<gt>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);

=over 4

=item obj: C<$s>
( C<L<Apache::ServerRec object|docs::2.0::api::Apache::ServerRec>> )

=item arg1: C<$file> ( string )

The file in which this function is called

=item arg2: C<$line> ( number )

The line number on which this function is called

=item arg3: C<$level>
( C<L<Apache::LOG_* constant|/LogLevel_Constants>> )

The level of this error message

=item arg4: C<$status>
( C<L<APR::Const status constant|docs::2.0::api::APR::Const>> )

The status code from the last command (similar to $! in perl), usually
C<L<APR::Const constant|docs::2.0::api::APR::Const>> or coming from an
L<exception object|docs::2.0::api::APR::Error>.

=item arg5: C<@message> ( strings ARRAY )

The log message(s)

=item ret: no return value

=item since: 1.99_12

=back

For example:

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





=head2 C<$s-E<gt>log>

get a log handle which can be used to L<log messages of different
levels|/LogLevel_Methods>.

  my $slog = $s->log;

=over 4

=item obj: C<$s>
( C<L<Apache::ServerRec object|docs::2.0::api::Apache::ServerRec>> )

=item ret: C<$slog> ( C<Apache::Log::Server> object )

C<Apache::Log::Server> object to be used with L<LogLevel
methods|/LogLevel_Methods>.

=item since: 1.99_12


=back







=head1 Request Logging Methods




=head2 C<$r-E<gt>log_error>

just logs the supplied message (similar to
C<L<$s-E<gt>log_error|/C__s_E_gt_log_error_>> ).

  $r->log_error(@message);

=over 4

=item obj: C<$r>
( C<L<Apache::RequestRec object|docs::2.0::api::Apache::RequestRec>> )

=item arg1: C<@message> ( strings ARRAY )

what to log

=item ret: no return value

=item since: 1.99_12


=back

For example:

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






=head2 C<$r-E<gt>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
C<L<$s-E<gt>log_serror|/C__s_E_gt_log_serror_>>.

=over 4

=item since: 1.99_12

=back

For example:

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





=head2 C<$r-E<gt>log>

get a log handle which can be used to L<log messages of different
levels|/LogLevel_Methods>.

  $rlog = $r->log;

=over 4

=item obj: C<$r> 
( C<L<Apache::RequestRec object|docs::2.0::api::Apache::RequestRec>> )

=item ret: C<$rlog> ( C<Apache::Log::Request> object )

C<Apache::Log::Request> object to be used with L<LogLevel
methods|/LogLevel_Methods>.

=item since: 1.99_12


=back






=head1 Other Logging Methods

=head2 LogLevel Methods

after getting the log handle with C<L<$s-E<gt>log|/C__s_E_gt_log_>> or
C<L<$r-E<gt>log|/C__s_E_gt_log_>>, use one of the following methods
(corresponding to the C<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);

=over 4

=item obj: C<$slog> ( L<server|/C__s_E_gt_log_> or
L<request|/C__s_E_gt_log_> log handle )

=item arg1: C<@message> ( strings ARRAY )

=item ret: no return value

=item since: 1.99_12

=back

For example if the C<LogLevel> is C<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
I<warn>, I<debug> and other logging command which are listed right to
I<error> will be disabled.



=head2 C<emerg>

See L<LogLevel Methods|/LogLevel_Methods>.



=head2 C<alert>

See L<LogLevel Methods|/LogLevel_Methods>.



=head2 C<crit>

See L<LogLevel Methods|/LogLevel_Methods>.



=head2 C<error>

See L<LogLevel Methods|/LogLevel_Methods>.



=head2 C<warn>

See L<LogLevel Methods|/LogLevel_Methods>.



=head2 C<notice>

See L<LogLevel Methods|/LogLevel_Methods>.


=head2 C<info>

See L<LogLevel Methods|/LogLevel_Methods>.


=head2 C<debug>

See L<LogLevel Methods|/LogLevel_Methods>.







=head1 General Functions





=head2 C<LOG_MARK>

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

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

=over 4

=item ret1: C<$file> ( string )

=item ret2: C<$line> ( number )

=item since: 1.99_12

=back

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., C<L<$s-E<gt>log_serror|/C__s_E_gt_log_serror_>> and
C<L<$r-E<gt>log_rerror|/C__r_E_gt_log_rerror_>> ).






=head1 Aliases

=head2 C<$s-E<gt>warn>

  $s->warn(@warnings);

is the same as:

  $s->log_error(Apache::Log::LOG_MARK, Apache::LOG_WARNING,
                APR::SUCCESS, @warnings)

For example:

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

=head2 C<Apache-E<gt>warn>

=head2 C<Apache::warn>

  Apache->warn(@warnings);




=head1 Unsupported API

C<Apache::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 L<the mod_perl development mailing
list|maillist::dev> so we can help each other take the steps necessary
to shift the method to an officially supported API.


=head2 C<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

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

=over 4

=item obj: C<$p> ( C<L<APR::Pool object|docs::2.0::api::APR::Pool>> )

The pool to use for logging

=item arg1: C<$fname> ( file path )

The name of the file to log to

=item ret: no return value

=item since: subject to change


=back






=head1 See Also

L<mod_perl 2.0 documentation|docs::2.0::index>.




=head1 Copyright

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




=head1 Authors

L<The mod_perl development team and numerous
contributors|about::contributors::people>.

=cut

