2 <!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">
3 <?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
6 Copyright 2002-2004 The Apache Software Foundation
8 Licensed under the Apache License, Version 2.0 (the "License");
9 you may not use this file except in compliance with the License.
10 You may obtain a copy of the License at
12 http://www.apache.org/licenses/LICENSE-2.0
14 Unless required by applicable law or agreed to in writing, software
15 distributed under the License is distributed on an "AS IS" BASIS,
16 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17 See the License for the specific language governing permissions and
18 limitations under the License.
21 <modulesynopsis metafile="mod_ldap.xml.meta">
24 <description>LDAP connection pooling and result caching services for use
25 by other LDAP modules</description>
26 <status>Experimental</status>
27 <sourcefile>util_ldap.c</sourcefile>
28 <identifier>ldap_module</identifier>
29 <compatibility>Available in version 2.0.41 and later</compatibility>
32 <p>This module was created to improve the performance of
33 websites relying on backend connections to LDAP servers. In
34 addition to the functions provided by the standard LDAP
35 libraries, this module adds an LDAP connection pool and an LDAP
36 shared memory cache.</p>
38 <p>To enable this module, LDAP support must be compiled into
39 apr-util. This is achieved by adding the <code>--with-ldap</code>
40 flag to the <code>./configure</code> script when building
43 <p>SSL support requires that <module>mod_ldap</module> be linked
44 with one of the following LDAP SDKs: <a href="http://www.openldap.org/">
45 OpenLDAP SDK</a> (both 1.x and 2.x), <a href="http://developer.novell.com/ndk/cldap.htm">
46 Novell LDAP SDK</a> or the <a href="http://www.iplanet.com/downloads/developer/">
47 iPlanet(Netscape)</a> SDK.</p>
51 <section id="exampleconfig"><title>Example Configuration</title>
52 <p>The following is an example configuration that uses
53 <module>mod_ldap</module> to increase the performance of HTTP Basic
54 authentication provided by <module>mod_auth_ldap</module>.</p>
57 # Enable the LDAP connection pool and shared<br />
58 # memory cache. Enable the LDAP cache status<br />
59 # handler. Requires that mod_ldap and mod_auth_ldap<br />
60 # be loaded. Change the "yourdomain.example.com" to<br />
61 # match your domain.<br />
63 LDAPSharedCacheSize 200000<br />
64 LDAPCacheEntries 1024<br />
65 LDAPCacheTTL 600<br />
66 LDAPOpCacheEntries 1024<br />
67 LDAPOpCacheTTL 600<br />
69 <Location /ldap-status><br />
71 SetHandler ldap-status<br />
72 Order deny,allow<br />
74 Allow from yourdomain.example.com<br />
75 AuthLDAPEnabled on<br />
76 AuthLDAPURL ldap://127.0.0.1/dc=example,dc=com?uid?one<br />
77 AuthLDAPAuthoritative on<br />
78 require valid-user<br />
84 <section id="pool"><title>LDAP Connection Pool</title>
86 <p>LDAP connections are pooled from request to request. This
87 allows the LDAP server to remain connected and bound ready for
88 the next request, without the need to unbind/connect/rebind.
89 The performance advantages are similar to the effect of HTTP
92 <p>On a busy server it is possible that many requests will try
93 and access the same LDAP server connection simultaneously.
94 Where an LDAP connection is in use, Apache will create a new
95 connection alongside the original one. This ensures that the
96 connection pool does not become a bottleneck.</p>
98 <p>There is no need to manually enable connection pooling in
99 the Apache configuration. Any module using this module for
100 access to LDAP services will share the connection pool.</p>
103 <section id="cache"><title>LDAP Cache</title>
105 <p>For improved performance, <module>mod_ldap</module> uses an aggressive
106 caching strategy to minimize the number of times that the LDAP
107 server must be contacted. Caching can easily double or triple
108 the throughput of Apache when it is serving pages protected
109 with mod_auth_ldap. In addition, the load on the LDAP server
110 will be significantly decreased.</p>
112 <p><module>mod_ldap</module> supports two types of LDAP caching during
113 the search/bind phase with a <em>search/bind cache</em> and
114 during the compare phase with two <em>operation
115 caches</em>. Each LDAP URL that is used by the server has
116 its own set of these three caches.</p>
118 <section id="search-bind"><title>The Search/Bind Cache</title>
119 <p>The process of doing a search and then a bind is the
120 most time-consuming aspect of LDAP operation, especially if
121 the directory is large. The search/bind cache is used to
122 cache all searches that resulted in successful binds.
123 Negative results (<em>i.e.</em>, unsuccessful searches, or searches
124 that did not result in a successful bind) are not cached.
125 The rationale behind this decision is that connections with
126 invalid credentials are only a tiny percentage of the total
127 number of connections, so by not caching invalid
128 credentials, the size of the cache is reduced.</p>
130 <p><module>mod_ldap</module> stores the username, the DN
131 retrieved, the password used to bind, and the time of the bind
132 in the cache. Whenever a new connection is initiated with the
133 same username, <module>mod_ldap</module> compares the password
134 of the new connection with the password in the cache. If the
135 passwords match, and if the cached entry is not too old,
136 <module>mod_ldap</module> bypasses the search/bind phase.</p>
138 <p>The search and bind cache is controlled with the <directive
139 module="mod_ldap">LDAPCacheEntries</directive> and <directive
140 module="mod_ldap">LDAPCacheTTL</directive> directives.</p>
143 <section id="opcaches"><title>Operation Caches</title>
144 <p>During attribute and distinguished name comparison
145 functions, <module>mod_ldap</module> uses two operation caches
146 to cache the compare operations. The first compare cache is
147 used to cache the results of compares done to test for LDAP
148 group membership. The second compare cache is used to cache
149 the results of comparisons done between distinguished
152 <p>The behavior of both of these caches is controlled with
153 the <directive module="mod_ldap">LDAPOpCacheEntries</directive>
154 and <directive module="mod_ldap">LDAPOpCacheTTL</directive>
158 <section id="monitoring"><title>Monitoring the Cache</title>
159 <p><module>mod_ldap</module> has a content handler that allows
160 administrators to monitor the cache performance. The name of
161 the content handler is <code>ldap-status</code>, so the
162 following directives could be used to access the
163 <module>mod_ldap</module> cache information:</p>
166 <Location /server/cache-info><br />
168 SetHandler ldap-status<br />
173 <p>By fetching the URL <code>http://servername/cache-info</code>,
174 the administrator can get a status report of every cache that is used
175 by <module>mod_ldap</module> cache. Note that if Apache does not
176 support shared memory, then each <code>httpd</code> instance has its
177 own cache, so reloading the URL will result in different
178 information each time, depending on which <code>httpd</code>
179 instance processes the request.</p>
183 <section id="usingssltls"><title>Using SSL</title>
185 <p>The ability to create an SSL connections to an LDAP server
186 is defined by the directives <directive module="mod_ldap">
187 LDAPTrustedCA</directive> and <directive module="mod_ldap">
188 LDAPTrustedCAType</directive>. These directives specify the certificate
189 file or database and the certificate type. Whenever the LDAP url
190 includes <em>ldaps://</em>, <module>mod_ldap</module> will establish
191 a secure connection to the LDAP server.</p>
194 # Establish an SSL LDAP connection. Requires that <br />
195 # mod_ldap and mod_auth_ldap be loaded. Change the <br />
196 # "yourdomain.example.com" to match your domain.<br />
198 LDAPTrustedCA /certs/certfile.der<br />
199 LDAPTrustedCAType DER_FILE<br />
201 <Location /ldap-status><br />
203 SetHandler ldap-status<br />
204 Order deny,allow<br />
206 Allow from yourdomain.example.com<br />
207 AuthLDAPEnabled on<br />
208 AuthLDAPURL ldaps://127.0.0.1/dc=example,dc=com?uid?one<br />
209 AuthLDAPAuthoritative on<br />
210 require valid-user<br />
215 <p>If <module>mod_ldap</module> is linked against the
216 Netscape/iPlanet LDAP SDK, it will not talk to any SSL server
217 unless that server has a certificate signed by a known Certificate
218 Authority. As part of the configuration
219 <module>mod_ldap</module> needs to be told where it can find
220 a database containing the known CAs. This database is in the same
221 format as Netscape Communicator's <code>cert7.db</code>
222 database. The easiest way to get this file is to start up a fresh
223 copy of Netscape, and grab the resulting
224 <code>$HOME/.netscape/cert7.db</code> file.</p>
229 <name>LDAPSharedCacheSize</name>
230 <description>Size in bytes of the shared-memory cache</description>
231 <syntax>LDAPSharedCacheSize <var>bytes</var></syntax>
232 <default>LDAPSharedCacheSize 102400</default>
233 <contextlist><context>server config</context></contextlist>
236 <p>Specifies the number of bytes to allocate for the shared
237 memory cache. The default is 100kb. If set to 0, shared memory
238 caching will not be used.</p>
243 <name>LDAPSharedCacheFile</name>
244 <description>Sets the shared memory chache file</description>
245 <syntax>LDAPSharedCacheFile <var>directory-path/filename</var></syntax>
246 <contextlist><context>server config</context></contextlist>
249 <p>Specifies the directory path and file name of the shared memory
250 cache file. If not set, shared memory caching will not be used.</p>
255 <name>LDAPCacheEntries</name>
256 <description>Maximum number of entries in the primary LDAP cache</description>
257 <syntax>LDAPCacheEntries <var>number</var></syntax>
258 <default>LDAPCacheEntries 1024</default>
259 <contextlist><context>server config</context></contextlist>
262 <p>Specifies the maximum size of the primary LDAP cache. This
263 cache contains successful search/binds. Set it to 0 to turn off
264 search/bind caching. The default size is 1024 cached
270 <name>LDAPCacheTTL</name>
271 <description>Time that cached items remain valid</description>
272 <syntax>LDAPCacheTTL <var>seconds</var></syntax>
273 <default>LDAPCacheTTL 600</default>
274 <contextlist><context>server config</context></contextlist>
277 <p>Specifies the time (in seconds) that an item in the
278 search/bind cache remains valid. The default is 600 seconds (10
284 <name>LDAPOpCacheEntries</name>
285 <description>Number of entries used to cache LDAP compare
286 operations</description>
287 <syntax>LDAPOpCacheEntries <var>number</var></syntax>
288 <default>LDAPOpCacheEntries 1024</default>
289 <contextlist><context>server config</context></contextlist>
292 <p>This specifies the number of entries <module>mod_ldap</module>
293 will use to cache LDAP compare operations. The default is 1024
294 entries. Setting it to 0 disables operation caching.</p>
299 <name>LDAPOpCacheTTL</name>
300 <description>Time that entries in the operation cache remain
302 <syntax>LDAPOpCacheTTL <var>seconds</var></syntax>
303 <default>LDAPOpCacheTTL 600</default>
304 <contextlist><context>server config</context></contextlist>
307 <p>Specifies the time (in seconds) that entries in the
308 operation cache remain valid. The default is 600 seconds.</p>
313 <name>LDAPTrustedCA</name>
314 <description>Sets the file containing the trusted Certificate Authority certificate or database</description>
315 <syntax>LDAPTrustedCA <var>directory-path/filename</var></syntax>
316 <contextlist><context>server config</context></contextlist>
319 <p>It specifies the directory path and file name of the trusted CA
320 <module>mod_ldap</module> should use when establishing an SSL
321 connection to an LDAP server. If using the Netscape/iPlanet Directory
322 SDK, the file name should be <code>cert7.db</code>.</p>
327 <name>LDAPTrustedCAType</name>
328 <description>Specifies the type of the Certificate Authority file</description>
329 <syntax>LDAPTrustedCAType <var>type</var></syntax>
330 <contextlist><context>server config</context></contextlist>
333 <p>The following types are supported:<br />
334 DER_FILE - file in binary DER format<br />
335 BASE64_FILE - file in Base64 format<br />
336 CERT7_DB_PATH - Netscape certificate database file ")</p>