Overview of new features in Apache HTTP Server 2.2 - Apache HTTP Server Version 2.4








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Apache HTTP Server Version 2.4



Apache > HTTP Server > Documentation > Version 2.4Overview of new features in Apache HTTP Server 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
See alsoComments


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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