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Apache HTTP Server Version 2.2
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Apache > HTTP Server > Documentation > Version 2.2
Overview of new features in Apache 2.2
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This document describes some of the major changes between the 2.0 and
2.2 versions of the Apache HTTP Server. For new features since version
1.3, see the 2.0 new features document.
* Core Enhancements
* Module Enhancements
* Program Enhancements
* Module Developer Changes
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Core Enhancements
Authn/Authz
The bundled authentication and authorization modules have been
refactored. The new mod_authn_alias module can greatly simplify
certain authentication configurations. See module name changes,
and the developer changes for more information about how these
changes affects users and module writers.
Caching
mod_cache, mod_disk_cache, and mod_mem_cache have undergone a
lot of changes, and are now considered production-quality.
htcacheclean has been introduced to clean up mod_disk_cache
setups.
Configuration
The default configuration layout has been simplified and
modularised. Configuration snippets which can be used to enable
commonly-used features are now bundled with Apache, and can be
easily added to the main server config.
Graceful stop
The prefork, worker and event MPMs now allow httpd to be
shutdown gracefully via the graceful-stop signal. The
GracefulShutdownTimeout directive has been added to specify an
optional timeout, after which httpd will terminate regardless of
the status of any requests being served.
Proxying
The new mod_proxy_balancer module provides load balancing
services for mod_proxy. The new mod_proxy_ajp module adds
support for the Apache JServ Protocol version 1.3 used by Apache
Tomcat.
Regular Expression Library Updated
Version 5.0 of the Perl Compatible Regular Expression Library
(PCRE) is now included. httpd can be configured to use a system
installation of PCRE by passing the --with-pcre flag to
configure.
Smart Filtering
mod_filter introduces dynamic configuration to the output filter
chain. It enables filters to be conditionally inserted, based on
any Request or Response header or environment variable, and
dispenses with the more problematic dependencies and ordering
problems in the 2.0 architecture.
Large File Support
httpd is now built with support for files larger than 2GB on
modern 32-bit Unix systems. Support for handling >2GB request
bodies has also been added.
Event MPM
The event MPM uses a separate thread to handle Keep Alive
requests and accepting connections. Keep Alive requests have
traditionally required httpd to dedicate a worker to handle it.
This dedicated worker could not be used again until the Keep
Alive timeout was reached.
SQL Database Support
mod_dbd, together with the apr_dbd framework, brings direct SQL
support to modules that need it. Supports connection pooling in
threaded MPMs.
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Module Enhancements
Authn/Authz
Modules in the aaa directory have been renamed and offer better
support for digest authentication. For example, mod_auth is now
split into mod_auth_basic and mod_authn_file; mod_auth_dbm is
now called mod_authn_dbm; mod_access has been renamed
mod_authz_host. There is also a new mod_authn_alias module for
simplifying certain authentication configurations.
mod_authnz_ldap
This module is a port of the 2.0 mod_auth_ldap module to the 2.2
Authn/Authz framework. New features include using LDAP attribute
values and complicated search filters in the Require directive.
mod_authz_owner
A new module that authorizes access to files based on the owner
of the file on the file system
mod_version
A new module that allows configuration blocks to be enabled
based on the version number of the running server.
mod_info
Added a new ?config argument which will show the configuration
directives as parsed by Apache, including their file name and
line number. The module also shows the order of all request
hooks and additional build information, similar to httpd -V.
mod_ssl
Added a support for RFC 2817, which allows connections to
upgrade from clear text to TLS encryption.
mod_imagemap
mod_imap has been renamed to mod_imagemap to avoid user
confusion.
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Program Enhancements
httpd
A new command line option -M has been added that lists all
modules that are loaded based on the current configuration.
Unlike the -l option, this list includes DSOs loaded via mod_so.
httxt2dbm
A new program used to generate dbm files from text input, for
use in RewriteMap with the dbm map type.
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Module Developer Changes
APR 1.0 API
Apache 2.2 uses the APR 1.0 API. All deprecated functions and
symbols have been removed from APR and APR-Util. For details,
see the APR Website.
Authn/Authz
The bundled authentication and authorization modules have been
renamed along the following lines:
+ mod_auth_* -> Modules that implement an HTTP authentication
mechanism
+ mod_authn_* -> Modules that provide a backend authentication
provider
+ mod_authz_* -> Modules that implement authorization (or
access)
+ mod_authnz_* -> Module that implements both authentication &
authorization
There is a new authentication backend provider scheme which
greatly eases the construction of new authentication backends.
Connection Error Logging
A new function, ap_log_cerror has been added to log errors that
occur with the client's connection. When logged, the message
includes the client IP address.
Test Configuration Hook Added
A new hook, test_config has been added to aid modules that want
to execute special code only when the user passes -t to httpd.
Set Threaded MPM's Stacksize
A new directive, ThreadStackSize has been added to set the stack
size on all threaded MPMs. This is required for some third-party
modules on platforms with small default thread stack size.
Protocol handling for output filters
In the past, every filter has been responsible for ensuring that
it generates the correct response headers where it affects them.
Filters can now delegate common protocol management to
mod_filter, using the ap_register_output_filter_protocol or
ap_filter_protocol calls.
Monitor hook added
Monitor hook enables modules to run regular/scheduled jobs in
the parent (root) process.
Regular expression API changes
The pcreposix.h header is no longer available; it is replaced by
the new ap_regex.h header. The POSIX.2 regex.h implementation
exposed by the old header is now available under the ap_
namespace from ap_regex.h. Calls to regcomp, regexec and so on
can be replaced by calls to ap_regcomp, ap_regexec.
DBD Framework (SQL Database API)
With Apache 1.x and 2.0, modules requiring an SQL backend had to
take responsibility for managing it themselves. Apart from
reinventing the wheel, this can be very inefficient, for example
when several modules each maintain their own connections.
Apache 2.1 and later provides the ap_dbd API for managing
database connections (including optimised strategies for
threaded and unthreaded MPMs), while APR 1.2 and later provides
the apr_dbd API for interacting with the database.
New modules SHOULD now use these APIs for all SQL database
operations. Existing applications SHOULD be upgraded to use it
where feasible, either transparently or as a recommended option
to their users.
Available Languages: en | fr | ko | pt-br | tr
Copyright 2009 The Apache Software Foundation.
Licensed under the Apache License, Version 2.0.
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