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- <h1 align="CENTER">Module mod_ldap</h1>
-
-<blockquote><strong>This module is not included with the standard
-distribution. It is available via CVS in the <a
-href="http://cvs.apache.org/viewcvs.cgi/httpd-ldap/">http-ldap</a>
-module.</strong></blockquote>
-
- <p>This module adds LDAP connection pooling and result caching
- to other Apache LDAP modules (like <a
- href="mod_auth_ldap.html">mod_auth_ldap</a>).</p>
-
- <p><a href="module-dict.html#Status"
- rel="Help"><strong>Status:</strong></a> Extension<br />
- <a href="module-dict.html#SourceFile"
- rel="Help"><strong>Source File:</strong></a> util_ldap.c<br />
- <a href="module-dict.html#ModuleIdentifier"
- rel="Help"><strong>Module Identifier:</strong></a>
- ldap_module<br />
- <a href="module-dict.html#Compatibility"
- rel="Help"><strong>Compatibility:</strong></a> Available in
- Apache 2.0 and later.</p>
-
- <h2>Summary</h2>
-
- <p>This module was created to improve the performance of
- websites relying on backend connections to LDAP servers. In
- addition to the functions provided by the standard LDAP
- libraries, this module adds an LDAP connection pool and an LDAP
- shared memory cache.</p>
-
- <p>To enable this module, LDAP support must be compiled into
- apr-util. This is achieved by adding the <em>--with-ldap</em>
- flag to the <tt>./configure</tt> script when building
- Apache.</p>
-
- <h2>Directives</h2>
-
- <ul>
- <li><a
- href="#LDAPCacheEntries"><tt>LDAPCacheEntries</tt></a></li>
-
- <li><a href="#LDAPCacheTTL"><tt>LDAPCacheTTL</tt></a></li>
-
- <li><a
- href="#LDAPCertDBPath"><tt>LDAPCertDBPath</tt></a></li>
-
- <li><a
- href="#LDAPOpCacheEntries"><tt>LDAPOpCacheEntries</tt></a></li>
-
- <li><a
- href="#LDAPOpCacheTTL"><tt>LDAPOpCacheTTL</tt></a></li>
-
- <li><a
- href="#LDAPSharedCacheSize"><tt>LDAPSharedCacheSize</tt></a></li>
- </ul>
-
- <h2>LDAP Connection Pool</h2>
-
- <p>LDAP connections are pooled from request to request. This
- allows the LDAP server to remain connected and bound ready for
- the next request, without the need to unbind/connect/rebind.
- The performance advantages are similar to the effect of HTTP
- keepalives.</p>
-
- <p>On a busy server it is possible that many requests will try
- and access the same LDAP server connection simultaneously.
- Where an LDAP connection is in use, Apache will create a new
- connection alongside the original one. This ensures that the
- connection pool does not become a bottleneck.</p>
-
- <p>There is no need to manually enable connection pooling in
- the Apache configuration. Any module using this module for
- access to LDAP services will share the connection pool.</p>
-
- <h2>LDAP Cache</h2>
-
- <p>For improved performance, mod_ldap uses an aggressive
- caching strategy to minimize the number of times that the LDAP
- server must be contacted. Caching can easily double or triple
- the throughput of Apache when it is serving pages protected
- with mod_auth_ldap. In addition, the load on the LDAP server
- will be significantly decreased.</p>
-
- <p>mod_ldap supports two types of LDAP caching during the
- search/bind phase with a <em><b>search/bind cache</b></em> and
- during the compare phase with two <em><b>operation
- caches</b></em>. Each LDAP URL that is used by the server has
- its own set of these three caches.</p>
-
- <ul>
- <li>
- <h3>The Search/Bind Cache</h3>
-
- <p>The process of doing a search and then a bind is the
- most time-consuming aspect of LDAP operation, especially if
- the directory is large. The search/bind cache is used to
- cache all searches that resulted in successful binds.
- Negative results (i.e., unsuccessful searches, or searches
- that did not result in a successful bind) are not cached.
- The rationale behind this decision is that connections with
- invalid credentials are only a tiny percentage of the total
- number of connections, so by not caching invalid
- credentials, the size of the cache is reduced.</p>
-
- <p>mod_ldap stores the username, the DN retrieved, the
- password used to bind, and the time of the bind in the
- cache. Whenever a new connection is initiated with the same
- username, mod_ldap compares the password of the new
- connection with the password in the cache. If the passwords
- match, and if the cached entry is not too old, mod_ldap
- bypasses the search/bind phase.</p>
-
- <p>The search and bind cache is controlled with the <a
- href="#LDAPCacheEntries"><tt>LDAPCacheEntries</tt></a> and
- <a href="#LDAPCacheTTL"><tt>LDAPCacheTTL</tt></a>
- directives.</p>
- </li>
-
- <li>
- <h3><a id="opcaches" name="opcaches">Operation
- Caches</a></h3>
-
- <p>During attribute and distinguished name comparison
- functions, mod_ldap uses two operation caches to cache the
- compare operations. The first compare cache is used to
- cache the results of compares done to test for LDAP group
- membership. The second compare cache is used to cache the
- results of comparisons done between distinguished
- names.</p>
-
- <p>The behavior of both of these caches is controlled with
- the <a
- href="#LDAPOpCacheEntries"><tt>LDAPOpCacheEntries</tt></a>
- and <a href="#LDAPOpCacheTTL"><tt>LDAPOpCacheTTL</tt></a>
- directives.</p>
- </li>
-
- <li>
- <h3>Monitoring the Cache</h3>
-
- <p>mod_ldap has a content handler that allows
- administrators to monitor the cache performance. The name
- of the content handler is <i>ldap-status</i>, so the
- following directives could be used to access the mod_ldap
- cache information:</p>
-<pre>
-<Location /server/cache-info >
- SetHandler ldap-status
-</Location>
-</pre>
-
- <p>By fetching the URL <i>http://servername/cache-info</i>,
- the administrator can get a status report of every cache
- that is used by mod_ldap cache. Note that if Apache does
- not support shared memory, then each <i>httpd</i> instance
- has its own cache, so reloading the URL will result in
- different information each time, depending on which
- <i>httpd</i> instance processes the request.</p>
- </li>
- </ul>
- <hr />
-
- <h2><a id="LDAPSharedCacheSize"
- name="LDAPSharedCacheSize">LDAPSharedCacheSize
- directive</a></h2>
-
- <p><a href="directive-dict.html#Syntax"
- rel="Help"><strong>Syntax:</strong></a> LDAPSharedCacheSize
- <em>bytes</em><br />
- <a href="directive-dict.html#Context"
- rel="Help"><strong>Context:</strong></a> server config<br />
- <a
- href="http://www.apache.org/docs/mod/directive-dict.html#Override"
- rel="Help"><strong>Override:</strong></a> Not Applicable<br />
- <a
- href="http://www.apache.org/docs/mod/directive-dict.html#Status"
- rel="Help"><strong>Status:</strong></a> Extension<br />
- <a
- href="http://www.apache.org/docs/mod/directive-dict.html#Module"
- rel="Help"><strong>Module:</strong></a> mod_ldap</p>
-
- <p>Specifies the number of bytes to specify for the shared
- memory cache. The default is 100kb.</p>
- <hr />
-
- <h2><a id="LDAPCacheEntries"
- name="LDAPCacheEntries">LDAPCacheEntries directive</a></h2>
-
- <p><a href="directive-dict.html#Syntax"
- rel="Help"><strong>Syntax:</strong></a>LDAPCacheEntries
- <em>size</em><br />
- <a href="directive-dict.html#Context"
- rel="Help"><strong>Context:</strong></a> server config<br />
- <a
- href="http://www.apache.org/docs/mod/directive-dict.html#Override"
- rel="Help"><strong>Override:</strong></a> Not Applicable<br />
- <a
- href="http://www.apache.org/docs/mod/directive-dict.html#Status"
- rel="Help"><strong>Status:</strong></a> Extension<br />
- <a
- href="http://www.apache.org/docs/mod/directive-dict.html#Module"
- rel="Help"><strong>Module:</strong></a> mod_ldap</p>
-
- <p>Specifies the maximum size of the primary LDAP cache. This
- cache contains successful search/binds. Set it to 0 to turn off
- search/bind caching. The default size is 1024 cached
- searches.</p>
- <hr />
-
- <h2><a id="LDAPCacheTTL" name="LDAPCacheTTL">LDAPCacheTTL
- directive</a></h2>
-
- <p><a href="directive-dict.html#Syntax"
- rel="Help"><strong>Syntax:</strong></a> LDAPCacheTTL
- <em>seconds</em><br />
- <a href="directive-dict.html#Context"
- rel="Help"><strong>Context:</strong></a> server config<br />
- <a
- href="http://www.apache.org/docs/mod/directive-dict.html#Override"
- rel="Help"><strong>Override:</strong></a> Not Applicable<br />
- <a
- href="http://www.apache.org/docs/mod/directive-dict.html#Status"
- rel="Help"><strong>Status:</strong></a> Extension<br />
- <a
- href="http://www.apache.org/docs/mod/directive-dict.html#Module"
- rel="Help"><strong>Module:</strong></a> mod_ldap</p>
-
- <p>Specifies the time (in seconds) that an item in the
- search/bind cache remains valid. The default is 600 seconds (10
- minutes).</p>
- <hr />
-
- <h2><a id="LDAPOpCacheEntries"
- name="LDAPOpCacheEntries">LDAPOpCacheEntries directive</a></h2>
-
- <p><a href="directive-dict.html#Syntax"
- rel="Help"><strong>Syntax:</strong></a> LDAPOpCacheEntries
- <em>seconds</em><br />
- <a href="directive-dict.html#Context"
- rel="Help"><strong>Context:</strong></a> server config<br />
- <a
- href="http://www.apache.org/docs/mod/directive-dict.html#Override"
- rel="Help"><strong>Override:</strong></a> Not Applicable<br />
- <a
- href="http://www.apache.org/docs/mod/directive-dict.html#Status"
- rel="Help"><strong>Status:</strong></a> Extension<br />
- <a
- href="http://www.apache.org/docs/mod/directive-dict.html#Module"
- rel="Help"><strong>Module:</strong></a> mod_ldap</p>
-
- <p>This specifies the number of entries mod_ldap will use to
- cache LDAP compare operations. The default is 1024 entries.
- Setting it to 0 disables operation caching.</p>
- <hr />
-
- <h2><a id="LDAPOpCacheTTL" name="LDAPOpCacheTTL">LDAPOpCacheTTL
- directive</a></h2>
-
- <p><a href="directive-dict.html#Syntax"
- rel="Help"><strong>Syntax:</strong></a> LDAPOpCacheTTL
- <em>seconds</em><br />
- <a href="directive-dict.html#Context"
- rel="Help"><strong>Context:</strong></a> server config<br />
- <a
- href="http://www.apache.org/docs/mod/directive-dict.html#Override"
- rel="Help"><strong>Override:</strong></a> Not Applicable<br />
- <a
- href="http://www.apache.org/docs/mod/directive-dict.html#Status"
- rel="Help"><strong>Status:</strong></a> Extension<br />
- <a
- href="http://www.apache.org/docs/mod/directive-dict.html#Module"
- rel="Help"><strong>Module:</strong></a> mod_ldap</p>
-
- <p>Specifies the time (in seconds) that entries in the
- operation cache remain valid. The default is 600 seconds.</p>
- <hr />
-
- <h2><a id="LDAPCertDBPath" name="LDAPCertDBPath">LDAPCertDBPath
- directive</a></h2>
-
- <p><a href="directive-dict.html#Syntax"
- rel="Help"><strong>Syntax:</strong></a> LDAPCertDBPath
- <em>directory-path</em><br />
- <a href="directive-dict.html#Context"
- rel="Help"><strong>Context:</strong></a> server config<br />
- <a
- href="http://www.apache.org/docs/mod/directive-dict.html#Override"
- rel="Help"><strong>Override:</strong></a> Not Applicable<br />
- <a
- href="http://www.apache.org/docs/mod/directive-dict.html#Status"
- rel="Help"><strong>Status:</strong></a> Extension<br />
- <a
- href="http://www.apache.org/docs/mod/directive-dict.html#Module"
- rel="Help"><strong>Module:</strong></a> mod_ldap</p>
-
- <p>This directive is only valid if Apache has been linked
- against the Netscape/iPlanet Directory SDK.</p>
-
- <p>It specifies in which directory mod_ldap should look for the
- certificate authorities database for SSL support. There should
- be a file named <tt>cert7.db</tt> in that directory.</p>
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