Apache HTTP Server Version 2.4
Apache HTTP Server Version 2.4
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.
mod_cache, mod_cache_disk, and
mod_mem_cache(already removed from 2.3/2.4) have undergone a lot of changes, and
are now considered production-quality. htcacheclean
has been introduced to clean up mod_cache_disk
setups.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.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.httpd can be
configured to use a system installation of PCRE by passing the
--with-pcre flag to configure.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.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 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.mod_dbd, together with the apr_dbd
framework, brings direct SQL support to modules that need it.
Supports connection pooling in threaded MPMs.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(already removed from 2.3/2.4) module for simplifying
certain authentication configurations.
mod_authnz_ldapmod_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_ownermod_versionmod_info?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_sslmod_imagemapmod_imap has been renamed to
mod_imagemap to avoid user confusion.httpd-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.httxt2dbmRewriteMap
with the dbm map type.APR and
APR-Util. For details, see the
APR Website.mod_auth_* -> Modules that implement an HTTP
authentication mechanismmod_authn_* -> Modules that provide a backend
authentication providermod_authz_* -> Modules that implement
authorization (or access)mod_authnz_* -> Module that implements both
authentication & authorizationap_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_config has been added to aid
modules that want to execute special code only when the user passes
-t to httpd.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.mod_filter, using the
ap_register_output_filter_protocol or
ap_filter_protocol calls.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.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.