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Man Pages


Manual Reference Pages  -  APACHE2::PERLSECTIONS (3)

.ds Aq ’

NAME

Apache2::PerlSections - write Apache configuration files in Perl

CONTENTS

Synopsis



  <Perl>
  @PerlModule = qw(Mail::Send Devel::Peek);
 
  #run the server as whoever starts it
  $User  = getpwuid(>) || >;
  $Group = getgrgid()) || );
 
  $ServerAdmin = $User;
 
  </Perl>



Description

With <Perl>...</Perl> sections, it is possible to configure your server entirely in Perl.

<Perl> sections can contain any and as much Perl code as you wish. These sections are compiled into a special package whose symbol table mod_perl can then walk and grind the names and values of Perl variables/structures through the Apache core configuration gears.

Block sections such as <Location>..</Location> are represented in a %Location hash, e.g.:



  <Perl>
  $Location{"/~dougm/"} = {
    AuthUserFile   => /tmp/htpasswd,
    AuthType       => Basic,
    AuthName       => test,
    DirectoryIndex => [qw(index.html index.htm)],
    Limit          => {
        "GET POST"    => {
            require => user dougm,
        }
    },
  };
  </Perl>



If an Apache directive can take two or three arguments you may push strings (the lowest number of arguments will be shifted off the @list) or use an array reference to handle any number greater than the minimum for that directive:



  push @Redirect, "/foo", "http://www.foo.com/";
 
  push @Redirect, "/imdb", "http://www.imdb.com/";
 
  push @Redirect, [qw(temp "/here" "http://www.there.com")];



Other section counterparts include %VirtualHost, %Directory and %Files.

To pass all environment variables to the children with a single configuration directive, rather than listing each one via PassEnv or PerlPassEnv, a <Perl> section could read in a file and:



  push @PerlPassEnv, [$key => $val];



or



  Apache2->httpd_conf("PerlPassEnv $key $val");



These are somewhat simple examples, but they should give you the basic idea. You can mix in any Perl code you desire. See eg/httpd.conf.pl and eg/perl_sections.txt in the mod_perl distribution for more examples.

Assume that you have a cluster of machines with similar configurations and only small distinctions between them: ideally you would want to maintain a single configuration file, but because the configurations aren’t exactly the same (e.g. the ServerName directive) it’s not quite that simple.

<Perl> sections come to rescue. Now you have a single configuration file and the full power of Perl to tweak the local configuration. For example to solve the problem of the ServerName directive you might have this <Perl> section:



  <Perl>
  $ServerName = `hostname`;
  </Perl>



For example if you want to allow personal directories on all machines except the ones whose names start with secure:



  <Perl>
  $ServerName = `hostname`;
  if ($ServerName !~ /^secure/) {
      $UserDir = "public.html";
  }
  else {
      $UserDir = "DISABLED";
  }
  </Perl>



API

Apache2::PerlSections provides the following functions and/or methods:

CWserver

Get the current server’s object for the <Perl> section



  <Perl>
    $s = Apache2::PerlSections->server();
  </Perl>



obj: Apache2::PerlSections (class name)
ret: $s ( Apache2::ServerRec object )
since: 2.0.03

@PerlConfig and $PerlConfig

This array and scalar can be used to introduce literal configuration into the apache configuration. For example:



  push @PerlConfig, Alias /foo /bar;



Or:
$PerlConfig .= Alias /foo /bar\n;

See also $r->add_config

Configuration Variables

There are a few variables that can be set to change the default behaviour of <Perl> sections.

CW$Apache2::PerlSections::Save

Each <Perl> section is evaluated in its unique namespace, by default residing in a sub-namespace of Apache2::ReadConfig::, therefore any local variables will end up in that namespace. For example if a <Perl> section happened to be in file /tmp/httpd.conf starting on line 20, the namespace: Apache2::ReadConfig::tmp::httpd_conf::line_20 will be used. Now if it had:



  <Perl>
    $foo     = 5;
    my $bar  = 6;
    $My::tar = 7;
  </Perl>



The local global variable $foo becomes $Apache2::ReadConfig::tmp::httpd_conf::line_20::foo, the other variable remain where they are.

By default, the namespace in which <Perl> sections are evaluated is cleared after each block closes. In our example nuking $Apache2::ReadConfig::tmp::httpd_conf::line_20::foo, leaving the rest untouched.

By setting $Apache2::PerlSections::Save to a true value, the content of those namespaces will be preserved and will be available for inspection by Apache2::Status and Apache2::PerlSections->dump In our example $Apache2::ReadConfig::tmp::httpd_conf::line_20::foo will still be accessible from other perl code, after the <Perl> section was parsed.

PerlSections Dumping

CWApache2::PerlSections->dump

This method will dump out all the configuration variables mod_perl will be feeding to the apache config gears. The output is suitable to read back in via eval.



  my $dump = Apache2::PerlSections->dump;



ret: $dump ( string / undef ) A string dump of all the Perl code encountered in <Perl> blocks, suitable to be read back via eval
For example:



  <Perl>
 
  $Apache2::PerlSections::Save = 1;
 
  $Listen = 8529;
 
  $Location{"/perl"} = {
     SetHandler => "perl-script",
     PerlHandler => "ModPerl::Registry",
     Options => "ExecCGI",
  };
 
  @DirectoryIndex = qw(index.htm index.html);
 
  $VirtualHost{"www.foo.com"} = {
     DocumentRoot => "/tmp/docs",
     ErrorLog => "/dev/null",
     Location => {
       "/" => {
         Allowoverride => All,
         Order => deny,allow,
         Deny  => from all,
         Allow => from foo.com,
       },
     },
  };
  </Perl>
 
  <Perl>
  print Apache2::PerlSections->dump;
  </Perl>



This will print something like this:



  $Listen = 8529;
 
  @DirectoryIndex = (
    index.htm,
    index.html
  );
 
  $Location{/perl} = (
      PerlHandler => Apache2::Registry,
      SetHandler => perl-script,
      Options => ExecCGI
  );
 
  $VirtualHost{www.foo.com} = (
      Location => {
        / => {
          Deny => from all,
          Order => deny,allow,
          Allow => from foo.com,
          Allowoverride => All
        }
      },
      DocumentRoot => /tmp/docs,
      ErrorLog => /dev/null
  );
 
  1;
  __END__



It is important to put the call to dump in it’s own <Perl> section, otherwise the content of the current <Perl> section will not be dumped.

CWApache2::PerlSections->store

This method will call the dump method, writing the output to a file, suitable to be pulled in via require or do.



  Apache2::PerlSections->store($filename);



arg1: $filename (string) The filename to save the dump output to
ret: no return value

Advanced API

mod_perl 2.0 now introduces the same general concept of handlers to <Perl> sections. Apache2::PerlSections simply being the default handler for them.

To specify a different handler for a given perl section, an extra handler argument must be given to the section:



  <Perl handler="My::PerlSection::Handler" somearg="test1">
    $foo = 1;
    $bar = 2;
  </Perl>



And in My/PerlSection/Handler.pm:



  sub My::Handler::handler : handler {
      my ($self, $parms, $args) = @_;
      #do your thing!
  }



So, when that given <Perl> block in encountered, the code within will first be evaluated, then the handler routine will be invoked with 3 arguments:
arg1: $self self-explanatory
arg2: $parms ( Apache2::CmdParms ) $parms is specific for the current Container, for example, you might want to call $parms->server() to get the current server.
arg3: $args ( APR::Table object) the table object of the section arguments. The 2 guaranteed ones will be:



  $args->{handler} = My::PerlSection::Handler;
  $args->{package} = Apache2::ReadConfig;



Other name="value" pairs given on the <Perl> line will also be included.

At this point, it’s up to the handler routing to inspect the namespace of the $args->{’package’} and chooses what to do.

The most likely thing to do is to feed configuration data back into apache. To do that, use Apache2::Server->add_config(directive), for example:



  $parms->server->add_config("Alias /foo /bar");



Would create a new alias. The source code of Apache2::PerlSections is a good place to look for a practical example.

Verifying <Perl> Sections

If the <Perl> sections include no code requiring a running mod_perl, it is possible to check those from the command line. But the following trick should be used:



  # file: httpd.conf
  <Perl>
  #!perl
 
  # ... code here ...
 
  __END__
  </Perl>



Now you can run:



  % perl -c httpd.conf



Bugs

    <Perl> directive missing closing ’>’

httpd-2.0.47 had a bug in the configuration parser which caused the startup failure with the following error:



  Starting httpd:
  Syntax error on line ... of /etc/httpd/conf/httpd.conf:
  <Perl> directive missing closing >     [FAILED]



This has been fixed in httpd-2.0.48. If you can’t upgrade to this or a higher version, please add a space before the closing ’>’ of the opening tag as a workaround. So if you had:



  <Perl>
  # some code
  </Perl>



change it to be:



  <Perl >
  # some code
  </Perl>



    <Perl>[...]> was not closed.

On encountering a one-line <Perl> block, httpd’s configuration parser will cause a startup failure with an error similar to this one:



  Starting httpd:
  Syntax error on line ... of /etc/httpd/conf/httpd.conf:
  <Perl>use> was not closed.



If you have written a simple one-line <Perl> section like this one :



  <Perl>use Apache::DBI;</Perl>



change it to be:



   <Perl>
   use Apache::DBI;
   </Perl>



This is caused by a limitation of httpd’s configuration parser and is not likely to be changed to allow one-line block like the example above. Use multi-line blocks instead.

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.
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perl v5.20.3 WORK::MOD_PERL-2.0.9::DOCS::API::APACHE2::PERLSECTIONS (3) 2015-06-18

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