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Пункт 3. New features with Apache 2.1/2.2
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
- Authn/Authz
- The bundled authentication and authorization modules have
been refactored. The new mod_authn_alias(already removed from 2.3/2.4)
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_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.
- 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.
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(already removed from 2.3/2.4) 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.
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.
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.
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