NAME

mod_perl 2.0 Server Configuration

Description

This chapter provides an in-depth mod_perl 2.0 configuration details.

mod_perl configuration directives

Similar to mod_perl 1.0, in order to use mod_perl 2.0 a few configuration settings should be added to httpd.conf. They are quite similar to 1.0 settings but some directives were renamed and new directives were added.

Enabling mod_perl

To enable mod_perl built as DSO add to httpd.conf:

LoadModule perl_module modules/mod_perl.so

This setting specifies the location of the mod_perl module relative to the ServerRoot setting, therefore you should put it somewhere after ServerRoot is specified.

If mod_perl has been statically linked it's automatically enabled.

Win32 users need to make sure that the path to the Perl binary (e.g., C:\Perl\bin) is in the PATH environment variable.

Accessing the mod_perl 2.0 Modules

In order to prevent from inadvertently loading mod_perl 1.0 modules mod_perl 2.0 Perl modules are installed into dedicated directories under Apache2/. The Apache2 module prepends the locations of the mod_perl 2.0 libraries to @INC, which are the same as the core @INC, but with Apache2/ appended. This module has to be loaded just after mod_perl has been enabled. This can be accomplished with:

use Apache2 ();

in the startup file. Only if you don't use a startup file you can add:

PerlModule Apache2

to httpd.conf, due to the order the PerlRequire and PerlModule directives are processed.

Startup File

Next usually a startup file with Perl code is loaded:

PerlRequire "/home/httpd/httpd-2.0/perl/startup.pl"

It's used to adjust Perl modules search paths in @INC, pre-load commonly used modules, pre-compile constants, etc. Here is a typical startup.pl for mod_perl 2.0:

file:startup.pl
---------------
use Apache2 ();

use lib qw(/home/httpd/perl);

# enable if the mod_perl 1.0 compatibility is needed
# use Apache::compat ();

use ModPerl::Util (); #for CORE::GLOBAL::exit

use Apache::RequestRec ();
use Apache::RequestIO ();
use Apache::RequestUtil ();

use Apache::Server ();
use Apache::ServerUtil ();
use Apache::Connection ();
use Apache::Log ();

use APR::Table ();

use ModPerl::Registry ();

use Apache::Const -compile => ':common';
use APR::Const -compile => ':common';

1;

In this file the Apache2 modules is loaded, so the 2.0 modules will be found. Afterwards @INC in adjusted to include non-standard directories with Perl modules:

use lib qw(/home/httpd/perl);

If you need to use the backwards compatibility layer load:

use Apache::compat ();

Next we preload the commonly used mod_perl 2.0 modules and precompile common constants.

Finally as usual the startup.pl file must be terminated with 1;.

Perl's Command Line Switches

Now you can pass any Perl's command line switches in httpd.conf using the PerlSwitches directive. For example to enable warnings and Taint checking add:

PerlSwitches -wT

As an alternative to using use lib in startup.pl to adjust @INC, now you can use the command line switch -I to do that:

PerlSwitches -I/home/stas/modperl

You could also use -Mlib=/home/stas/modperl which is the exact equivalent as use lib, but it's broken on certain platforms/version (e.g. Darwin/5.6.0). use lib is removing duplicated entries, whereas -I does not.

mod_perl 2.0 Handlers

mod_perl 2.0 provides two types of handlers: modperl and perl-script.

modperl

Configured as:

SetHandler modperl

The bare mod_perl handler type, which just calls the Perl*Handler's callback function. If you don't need the features provided by the perl-script handler, with the modperl handler, you can gain even more performance. (This handler isn't available in mod_perl 1.0.)

Unless the Perl*Handler callback running under the modperl handler is configured with:

PerlOptions +SetupEnv

or calls:

$r->subprocess_env;

in a void context (which has the same effect as PerlOptions +SetupEnv for the handler that called it), only the following environment variables are accessible via %ENV:

MOD_PERL and GATEWAY_INTERFACE (always)
PATH and TZ (if you had them defined in the shell or httpd.conf)

Therefore if you don't want to add the overhead of populating %ENV, when you simply want to pass some configuration variables from httpd.conf, consider using PerlSetVar and PerlAddVar instead of PerlSetEnv and PerlPassEnv. In your code you can retrieve the values using the dir_config() method. For example if you set in httpd.conf:

<Location /print_env2>
    SetHandler modperl
    PerlResponseHandler Apache::VarTest
    PerlSetVar VarTest VarTestValue
</Location>

this value can be retrieved inside Apache::VarTest::handler() with:

$r->dir_config('VarTest');

Alternatively use the Apache core directives SetEnv and PassEnv, which always populate r->subprocess_env, but this doesn't happen until the Apache fixups phase, which could be too late for your needs.

perl-script

Configured as:

SetHandler perl-script

Most mod_perl handlers use the perl-script handler. Among other things it does:

PerlOptions +GlobalRequest is in effect unless:
```
PerlOptions -GlobalRequest
```
is specified.
PerlOptions +SetupEnv is in effect unless:
```
PerlOptions -SetupEnv
```
is specified.
STDOUT and STDOUT get tied to the request object $r, which makes possible to read from STDIN and print directly to STDOUT via CORE::print(), instead of implicit calls like $r->puts().
Several special global Perl variables are saved before the handler is called and restored afterwards (similar to mod_perl 1.0). This includes: %ENV, @INC, $/, STDOUT's $| and END blocks array (PL_endav).

`PerlOptions` Directive

The directive PerlOptions provides fine-grained configuration for what were compile-time only options in the first mod_perl generation. It also provides control over what class of PerlInterpreter is used for a <VirtualHost> or location configured with <Location>, <Directory>, etc.

Options are enabled by prepending + and disabled with -. The options include:

`Enable`

On by default, can be used to disable mod_perl for a given VirtualHost. For example:

<VirtualHost ...>
    PerlOptions -Enable
</VirtualHost>

`Clone`

Share the parent Perl interpreter, but give the VirtualHost its own interpreter pool. For example should you wish to fine tune interpreter pools for a given virtual host:

<VirtualHost ...>
    PerlOptions +Clone
    PerlInterpStart 2
    PerlInterpMax 2
</VirtualHost>

This might be worthwhile in the case where certain hosts have their own sets of large-ish modules, used only in each host. By tuning each host to have its own pool, that host will continue to reuse the Perl allocations in their specific modules.

When cloning a Perl interpreter, to inherit base Perl interpreter's PerlSwitches use:

<VirtualHost ...>
    ...
    PerlSwitches +inherit
</VirtualHost>

`Parent`

Create a new parent Perl interpreter for the given VirtualHost and give it its own interpreter pool (implies the Clone option).

A common problem with mod_perl 1.0 was the shared namespace between all code within the process. Consider two developers using the same server and each wants to run a different version of a module with the same name. This example will create two parent Perl interpreters, one for each <VirtualHost>, each with its own namespace and pointing to a different paths in @INC:

META: is -Mblib portable? (problems with -Mlib on Darwin/5.6.0?)

<VirtualHost ...>
    ServerName dev1
    PerlOptions +Parent
    PerlSwitches -Mblib=/home/dev1/lib/perl
</VirtualHost>

<VirtualHost ...>
    ServerName dev2
    PerlOptions +Parent
    PerlSwitches -Mblib=/home/dev2/lib/perl
</VirtualHost>

Or even for a given location, for something like "dirty" cgi scripts:

<Location /cgi-bin>
    PerlOptions +Parent
    PerlInterpMaxRequests 1
    PerlInterpStart 1
    PerlInterpMax 1
    PerlResponseHandler ModPerl::Registry
</Location>

will use a fresh interpreter with its own namespace to handle each request.

`Perl*Handler`

Disable Perl*Handlers, all compiled-in handlers are enabled by default. The option name is derived from the Perl*Handler name, by stripping the Perl and Handler parts of the word. So PerlLogHandler becomes Log which can be used to disable PerlLogHandler:

PerlOptions -Log

Suppose one of the hosts does not want to allow users to configure PerlAuthenHandler, PerlAuthzHandler, PerlAccessHandler and <Perl> sections:

<VirtualHost ...>
    PerlOptions -Authen -Authz -Access -Sections
</VirtualHost>

Or maybe everything but the response handler:

<VirtualHost ...>
    PerlOptions None +Response
</VirtualHost>

`AutoLoad`

Resolve Perl*Handlers at startup time, which includes loading the modules from disk if not already loaded.

In mod_perl 1.0, configured Perl*Handlers which are not a fully qualified subroutine names are resolved at request time, loading the handler module from disk if needed. In mod_perl 2.0, configured Perl*Handlers are resolved at startup time. By default, modules are not auto-loaded during startup-time resolution. It is possible to enable this feature with:

PerlOptions +Autoload

Consider this configuration:

PerlResponseHandler Apache::Magick

In this case, Apache::Magick is the package name, and the subroutine name will default to handler. If the Apache::Magick module is not already loaded, PerlOptions +Autoload will attempt to pull it in at startup time. With this option enabled you don't have to explicitly load the handler modules. For example you don't need to add:

PerlModule Apache::Magick

in our example.

`GlobalRequest`

Setup the global request_rec for use with Apache->request. This setting is needed for example if you use CGI.pm to process the incoming request.

This setting is enabled by default for sections configured as:

<Location ...>
    SetHandler perl-script
    ...
</Location>

And can be disabled with:

<Location ...>
    SetHandler perl-script
    PerlOptions -GlobalRequest
    ...
</Location>

`ParseHeaders`

Scan output for HTTP headers, same functionality as mod_perl 1.0's PerlSendHeader, but more robust. This option is usually needs to be enabled for registry scripts which send the HTTP header with:

print "Content-type: text/html\n\n";

`MergeHandlers`

Turn on merging of Perl*Handler arrays. For example with a setting:

PerlFixupHandler Apache::FixupA

<Location /inside>
    PerlFixupHandler Apache::FixupB
</Location>

a request for /inside only runs Apache::FixupB (mod_perl 1.0 behavior). But with this configuration:

PerlFixupHandler Apache::FixupA

<Location /inside>
    PerlOptions +MergeHandlers
    PerlFixupHandler Apache::FixupB
</Location>

a request for /inside will run both Apache::FixupA and Apache::FixupB handlers.

`SetupEnv`

Set up environment variables for each request ala mod_cgi.

When this option is enabled, mod_perl fiddles with the environment to make it appear as if the code is called under the mod_cgi handler. For example, the $ENV{QUERY_STRING} environment variable is initialized with the contents of Apache::args(), and the value returned by Apache::server_hostname() is put into $ENV{SERVER_NAME}.

But %ENV population is expensive. Those who have moved to the Perl Apache API no longer need this extra %ENV population, and can gain by disabling it. A code using the CGI.pm module require PerlOptions +SetupEnv because that module relies on a properly populated CGI environment table.

This option is enabled by default for sections configured as:

<Location ...>
    SetHandler perl-script
    ...
</Location>

Since this option adds an overhead to each request, if you don't need this functionality you can turn it off for a certain section:

<Location ...>
    SetHandler perl-script
    PerlOptions -SetupEnv
    ...
</Location>

or globally:

PerlOptions -SetupEnv
<Location ...>
    ...
</Location>

and then it'll affect the whole server. It can still be enabled for sections that need this functionality.

When this option is disabled you can still read environment variables set by you. For example when you use the following configuration:

PerlOptions -SetupEnv
PerlModule Modperl::Registry
<Location /perl>
  PerlSetEnv TEST hi
  SetHandler perl-script
  PerlHandler ModPerl::Registry
  Options +ExecCGI
</Location>

and you issue a request for this script:

setupenvoff.pl
--------------
use Data::Dumper;
my $r = Apache->request();
$r->send_http_header('text/plain');
print Dumper(\%ENV);

you should see something like this:

$VAR1 = {
          'GATEWAY_INTERFACE' => 'CGI-Perl/1.1',
          'MOD_PERL' => 'mod_perl/2.0.1',
          'PATH' => 'bin:/usr/bin',
          'TEST' => 'hi'
        };

Notice that we have got the value of the environment variable TEST.

Handlers Directives

See The handlers chapters.

Threads Mode Specific Directives

These directives are enabled only in a threaded mod_perl+Apache combo:

`PerlInterpStart`

The number of interpreters to clone at startup time.

`PerlInterpMax`

If all running interpreters are in use, mod_perl will clone new interpreters to handle the request, up until this number of interpreters is reached. when PerlInterpMax is reached, mod_perl will block (via COND_WAIT()) until one becomes available (signaled via COND_SIGNAL()).

`PerlInterpMinSpare`

The minimum number of available interpreters this parameter will clone interpreters up to PerlInterpMax, before a request comes in.

`PerlInterpMaxSpare`

mod_perl will throttle down the number of interpreters to this number as those in use become available.

`PerlInterpMaxRequests`

The maximum number of requests an interpreter should serve, the interpreter is destroyed when the number is reached and replaced with a fresh clone.

`PerlInterpScope`

As mentioned, when a request in a threaded mpm is handled by mod_perl, an interpreter must be pulled from the interpreter pool. The interpreter is then only available to the thread that selected it, until it is released back into the interpreter pool. By default, an interpreter will be held for the lifetime of the request, equivalent to this configuration:

PerlInterpScope request

For example, if a PerlAccessHandler is configured, an interpreter will be selected before it is run and not released until after the logging phase.

Interpreters will be shared across sub-requests by default, however, it is possible to configure the interpreter scope to be per-sub-request on a per-directory basis:

PerlInterpScope subrequest

With this configuration, an autoindex generated page, for example, would select an interpreter for each item in the listing that is configured with a Perl*Handler.

It is also possible to configure the scope to be per-handler:

PerlInterpScope handler

With this configuration, an interpreter will be selected before PerlAccessHandlers are run, and put back immediately afterwards, before Apache moves onto the authentication phase. If a PerlFixupHandler is configured further down the chain, another interpreter will be selected and again put back afterwards, before PerlResponseHandler is run.

For protocol handlers, the interpreter is held for the lifetime of the connection. However, a C protocol module might hook into mod_perl (e.g. mod_ftp) and provide a request_rec record. In this case, the default scope is that of the request. Should a mod_perl handler want to maintain state for the lifetime of an ftp connection, it is possible to do so on a per-virtualhost basis:

PerlInterpScope connection

mod_perl Directives Argument Types and Allowed Location

The following table shows where in the configuration files mod_perl configuration directives are allowed to appear, what kind and how many arguments they expect:

General directives:

  Directive                 Arguments  Scope
--------------------------------------------
PerlSwitches                 ITERATE    SRV
PerlRequire                  ITERATE    SRV
PerlModule                   ITERATE    SRV
PerlOptions                  ITERATE    DIR
PerlSetVar                   TAKE2      DIR
PerlAddVar                   ITERATE2   DIR
PerlSetEnv                   TAKE2      DIR
PerlPassEnv                  TAKE1      SRV
<Perl> Sections              RAW_ARGS   SRV
PerlTrace                    TAKE1      SRV

Handler assignment directives:

  Directive                 Arguments  Scope
--------------------------------------------
PerlOpenLogsHandler          ITERATE    SRV
PerlPostConfigHandler        ITERATE    SRV
PerlChildInitHandler         ITERATE    SRV

PerlPreConnectionHandler     ITERATE    SRV
PerlProcessConnectionHandler ITERATE    SRV

PerlPostReadRequestHandler   ITERATE    SRV
PerlTransHandler             ITERATE    SRV
PerlInitHandler              ITERATE    DIR
PerlHeaderParserHandler      ITERATE    DIR
PerlAccessHandler            ITERATE    DIR
PerlAuthenHandler            ITERATE    DIR
PerlAuthzHandler             ITERATE    DIR
PerlTypeHandler              ITERATE    DIR
PerlFixupHandler             ITERATE    DIR
PerlResponseHandler          ITERATE    DIR
PerlLogHandler               ITERATE    DIR
PerlCleanupHandler           ITERATE    DIR

PerlInputFilterHandler       ITERATE    DIR
PerlOutputFilterHandler      ITERATE    DIR

Perl Interpreter management directives:

  Directive                 Arguments  Scope
--------------------------------------------
PerlInterpStart              TAKE1      SRV
PerlInterpMax                TAKE1      SRV
PerlInterpMinSpare           TAKE1      SRV
PerlInterpMaxSpare           TAKE1      SRV
PerlInterpMaxRequests        TAKE1      SRV
PerlInterpScope              TAKE1      DIR

mod_perl 1.0 back-compatibility directives:

  Directive                 Arguments  Scope
--------------------------------------------
PerlHandler                   ITERATE   DIR
PerlSendHeader                FLAG      DIR
PerlSetupEnv                  FLAG      DIR
PerlTaintCheck                FLAG      SRV
PerlWarn                      FLAG      SRV

The Arguments column represents the type of arguments directives accepts, where:

ITERATE: Expects a list of arguments.
ITERATE2: Expects one argument, followed by at least one or more arguments.
TAKE1: Expects one argument only.
TAKE2: Expects two arguments only.
FLAG: One of On or Off (case insensitive).
RAW_ARGS: The function parses the command line by itself.

The Scope column shows the location the directives are allowed to appear in:

SRV

Global configuration and <VirtualHost> (mnemonic: SeRVer). These directives are defined as RSRC_CONF in the source code.

DIR

<Directory>, <Location>, <Files> and all their regular expression variants (mnemonic: DIRectory). These directives can also appear in .htaccess files. These directives are defined as OR_ALL in the source code.

These directives can also appear in the global server configuration and <VirtualHost>.

Apache specifies other allowed location types which are currently not used by the core mod_perl directives and their definition can be found in include/httpd_config.h (hint: search for RSRC_CONF).

Also see Single Phase's Multiple Handlers Behavior.

Server Startup Options Retrieval

Inside httpd.conf one can do conditional configuration based on the define options passed at the server startup. For example:

<IfDefine PERLDB>
    <Perl>
        use Apache::DB ();
        Apache::DB->init;
    </Perl>
  
    <Location />
        PerlFixupHandler Apache::DB
    </Location>
</IfDefine>

So only when the server is started as:

% httpd C<-DPERLDB> ...

The configuration inside IfDefine will have an effect. If you want to have some configuration section to have an effect if a certain define wasn't defined use !, for example here is the opposite of the previous example:

<IfDefine !PERLDB>
    # ...
</IfDefine>

If you need to access any of the startup defines in the Perl code you use Apache::exists_config_define. For example in a startup file you can say:

use Apache::ServerUtil ();
if (Apache::exists_config_define("PERLDB")) {
    require Apache::DB;
    Apache::DB->init;
}

For example to check whether the server has been started in a single mode use:

if (Apache::exists_config_define("ONE_PROCESS")) {
    print "Running in a single mode";
}

MODPERL2 Define Option

When running under mod_perl 2.0 a special configuration define MODPERL2 is enabled internally, as if the server had been started with -DMODPERL2. For example this can be used to write a configuration file which needs to do something different whether it's running under mod_perl 1.0 or 2.0:

<IfDefine MODPERL2>
    # 2.0 configuration
</IfDefine>
<IfDefine !MODPERL2>
    # else
</IfDefine>

From within Perl code this can be tested with Apache::exists_config_define(), for example:

if (Apache::exists_config_define("MODPERL2")) {
    # some 2.0 specific code
}

Perl Interface to the Apache Configuration Tree

META:

Apache::Directive

t/response/TestApache/conftree.pm

Debug Directives

`PerlTrace [level]`

set the trace level. This directive is enabled when mod_perl is compiled with the MP_TRACE option. level is either:

all

which sets maximum logging and debugging levels;

a combination of one or more option letters (or option numerical equivalents) from the following list:

d (  1) directive processing
f (  2) filters
g (  4) Perl runtime interaction
h (  8) handlers
i ( 16) interpreter pool management
m ( 32) memory allocations
s ( 64) perl sections
t (128) benchmark-ish timings

When level is not specified, the tracing level will be set to the value of the MOD_PERL_TRACE environment variable.

Maintainers

Maintainer is the person(s) you should contact with updates, corrections and patches.

Doug MacEachern <dougm (at) covalent.net>
Stas Bekman <stas (at) stason.org>

Authors

Doug MacEachern <dougm (at) covalent.net>

Only the major authors are listed above. For contributors see the Changes file.

To install mod_perl, copy and paste the appropriate command in to your terminal.

cpanm

cpanm mod_perl

CPAN shell

perl -MCPAN -e shell
install mod_perl

For more information on module installation, please visit the detailed CPAN module installation guide.

	Global
`s`	Focus search bar
`?`	Bring up this help dialog

	GitHub
`g` `p`	Go to pull requests
`g` `i`	Go to GitHub issues (only if GitHub is preferred repository)

	POD
`g` `a`	Go to author
`g` `c`	Go to changes
`g` `i`	Go to issues
`g` `d`	Go to dist
`g` `r`	Go to repository/SCM
`g` `s`	Go to source
`g` `b`	Go to file browse

Search terms
module: (e.g. module:Plugin)
distribution: (e.g. distribution:Dancer auth)
author: (e.g. author:SONGMU Redis)
version: (e.g. version:1.00)

NAME

Description

mod_perl configuration directives

Enabling mod_perl

Accessing the mod_perl 2.0 Modules

Startup File

Perl's Command Line Switches

mod_perl 2.0 Handlers

modperl

perl-script

PerlOptions Directive

Enable

Clone

Parent

Perl*Handler

AutoLoad

GlobalRequest

ParseHeaders

MergeHandlers

SetupEnv