2 # Copyright 2007 The OpenLDAP Foundation, All Rights Reserved.
3 # COPYING RESTRICTIONS APPLY, see COPYRIGHT.
5 H1: Changes Since Previous Release
7 The following sections attempt to summarize the new features and changes in OpenLDAP
8 software since the 2.3.x release and the OpenLDAP Admin Guide.
10 H2: New Guide Sections
12 In order to make the Admin Guide more thorough and cover the majority of questions
13 asked on the OpenLDAP mailing lists and scenarios discussed there, we have added the following new sections:
15 * {{SECT:When should I use LDAP?}}
16 * {{SECT:When should I not use LDAP?}}
17 * {{SECT:LDAP vs RDBMS}}
20 * {{SECT:Replication}}
21 * {{SECT:Maintenance}}
24 * {{SECT:Troubleshooting}}
25 * {{SECT:Changes Since Previous Release}}
26 * {{SECT:Upgrading from 2.3.x}}
27 * {{SECT:Common errors encountered when using OpenLDAP Software}}
28 * {{SECT:Recommended OpenLDAP Software Dependency Versions}}
29 * {{SECT:Real World OpenLDAP Deployments and Examples}}
30 * {{SECT:OpenLDAP Software Contributions}}
31 * {{SECT:Configuration File Examples}}
32 * {{SECT:LDAP Result Codes}}
35 Also, the table of contents is now 3 levels deep to ease navigation.
38 H2: New Features and Enhancements in 2.4
40 H3: Better {{B:cn=config}} functionality
42 There is a new slapd-config(5) manpage for the {{B:cn=config}} backend. The
43 original design called for auto-renaming of config entries when you insert or
44 delete entries with ordered names, but that was not implemented in 2.3. It is
45 now in 2.4. This means, e.g., if you have
47 > olcDatabase={1}bdb,cn=config
48 > olcSuffix: dc=example,dc=com
50 and you want to add a new subordinate, now you can ldapadd:
52 > olcDatabase={1}bdb,cn=config
53 > olcSuffix: dc=foo,dc=example,dc=com
55 This will insert a new BDB database in slot 1 and bump all following databases
56 down one, so the original BDB database will now be named:
58 > olcDatabase={2}bdb,cn=config
59 > olcSuffix: dc=example,dc=com
61 H3: Better {{B:cn=schema}} functionality
63 In 2.3 you were only able to add new schema elements, not delete or modify
64 existing elements. In 2.4 you can modify schema at will. (Except for the
65 hardcoded system schema, of course.)
67 H3: More sophisticated Syncrepl configurations
69 The original implementation of Syncrepl in OpenLDAP 2.2 was intended to support
70 multiple consumers within the same database, but that feature never worked and
71 was removed from OpenLDAP 2.3; you could only configure a single consumer in
74 In 2.4 you can configure multiple consumers in a single database. The configuration
75 possibilities here are quite complex and numerous. You can configure consumers
76 over arbitrary subtrees of a database (disjoint or overlapping). Any portion
77 of the database may in turn be provided to other consumers using the Syncprov
78 overlay. The Syncprov overlay works with any number of consumers over a single
79 database or over arbitrarily many glued databases.
81 H3: N-Way Multimaster Replication
83 As a consequence of the work to support multiple consumer contexts, the syncrepl
84 system now supports full N-Way multimaster replication with entry-level conflict
85 resolution. There are some important constraints, of course: In order to maintain
86 consistent results across all servers, you must maintain tightly synchronized
87 clocks across all participating servers (e.g., you must use NTP on all servers).
89 The entryCSNs used for replication now record timestamps with microsecond resolution,
90 instead of just seconds. The delta-syncrepl code has not been updated to support
91 multimaster usage yet, that will come later in the 2.4 cycle.
93 H3: Replicating {{slapd}} Configuration (syncrepl and {{B:cn=config}})
95 Syncrepl was explicitly disabled on cn=config in 2.3. It is now fully supported
96 in 2.4; you can use syncrepl to replicate an entire server configuration from
97 one server to arbitrarily many other servers. It's possible to clone an entire
98 running slapd using just a small (less than 10 lines) seed configuration, or
99 you can just replicate the schema subtrees, etc. Tests 049 and 050 in the test
100 suite provide working examples of these capabilities.
103 H3: Push-Mode Replication
105 In 2.3 you could configure syncrepl as a full push-mode replicator by using it
106 in conjunction with a back-ldap pointed at the target server. But because the
107 back-ldap database needs to have a suffix corresponding to the target's suffix,
108 you could only configure one instance per slapd.
110 In 2.4 you can define a database to be "hidden", which means that its suffix is
111 ignored when checking for name collisions, and the database will never be used
112 to answer requests received by the frontend. Using this "hidden" database feature
113 allows you to configure multiple databases with the same suffix, allowing you to
114 set up multiple back-ldap instances for pushing replication of a single database
115 to multiple targets. There may be other uses for hidden databases as well (e.g.,
116 using a syncrepl consumer to maintain a *local* mirror of a database on a separate filesystem).
119 H3: More extensive TLS configuration control
121 In 2.3, the TLS configuration in slapd was only used by the slapd listeners. For
122 outbound connections used by e.g. back-ldap or syncrepl their TLS parameters came
123 from the system's ldap.conf file.
125 In 2.4 all of these sessions inherit their settings from the main slapd configuration,
126 but settings can be individually overridden on a per-config-item basis. This is
127 particularly helpful if you use certificate-based authentication and need to use a
128 different client certificate for different destinations.
131 H3: Performance enhancements
133 Too many to list. Some notable changes - ldapadd used to be a couple of orders
134 of magnitude slower than "slapadd -q". It's now at worst only about half the
135 speed of slapadd -q. Some comparisons of all the 2.x OpenLDAP releases are available
136 at {{URL:http://www.openldap.org/pub/hyc/scale2007.pdf}}
138 That compared 2.0.27, 2.1.30, 2.2.30, 2.3.33, and HEAD). Toward the latter end
139 of the "Cached Search Performance" chart it gets hard to see the difference
140 because the run times are so small, but the new code is about 25% faster than 2.3,
141 which was about 20% faster than 2.2, which was about 100% faster than 2.1, which
142 was about 100% faster than 2.0, in that particular search scenario. That test
143 basically searched a 1.3GB DB of 380836 entries (all in the slapd entry cache)
144 in under 1 second. i.e., on a 2.4GHz CPU with DDR400 ECC/Registered RAM we can
145 search over 500 thousand entries per second. The search was on an unindexed
146 attribute using a filter that would not match any entry, forcing slapd to examine
147 every entry in the DB, testing the filter for a match.
149 Essentially the slapd entry cache in back-bdb/back-hdb is so efficient the search
150 processing time is almost invisible; the runtime is limited only by the memory
151 bandwidth of the machine. (The search data rate corresponds to about 3.5GB/sec;
152 the memory bandwidth on the machine is only about 4GB/sec due to ECC and register latency.)
156 * slapo-constraint (Attribute value constraints)
157 * slapo-dds (Dynamic Directory Services, RFC 2589)
158 * slapo-memberof (reverse group membership maintenance)
160 H3: New features in existing Overlays
163 - Inspection/Maintenance
164 -- the cache database can be directly accessed via
165 LDAP by adding a specific control to each LDAP request; a specific
166 extended operation allows to consistently remove cached entries and entire
169 -- cached queries are saved on disk at shutdown, and reloaded if
170 not expired yet at subsequent restart
172 * slapo-rwm can safely interoperate with other overlays
173 * Dyngroup/Dynlist merge, plus security enhancements
174 - added dgIdentity support (draft-haripriya-dynamicgroup)
176 H3: New features in slapd
178 * monitoring of back-{b,h}db: cache fill-in, non-indexed searches,
179 * session tracking control (draft-wahl-ldap-session)
180 * subtree delete in back-sql (draft-armijo-ldap-treedelete)
182 H3: New features in libldap
184 * ldap_sync client API (LDAP Content Sync Operation, RFC 4533)
186 H3: New clients, tools and tool enhancements
188 * ldapexop for arbitrary extended operations
189 * Complete support of controls in request/response for all clients
190 * LDAP Client tools now honor SRV records
192 H3: New build options
194 * Support for building against GnuTLS
197 H2: Obsolete Features Removed From 2.4
199 These features were strongly deprecated in 2.3 and removed in 2.4.
203 Please read the {{SECT:Replication}} section as to why this is no longer in
208 back-ldbm was both slow and unreliable. Its byzantine indexing code was
209 prone to spontaneous corruption, as were the underlying database libraries
210 that were commonly used (e.g. GDBM or NDBM). back-bdb and back-hdb are
211 superior in every aspect, with simplified indexing to avoid index corruption,
212 fine-grained locking for greater concurrency, hierarchical caching for
213 greater performance, streamlined on-disk format for greater efficiency
214 and portability, and full transaction support for greater reliability.