4 As of version 2.0.0, the load balance documentation is in the
5 available in the "unlang" man page. The text below may not be up to
6 date, and is here only for historical purposes.
8 As of version 1.1.0, FreeRADIUS supports load balancing in module
9 sections. Please see the "configurable_failover" file in this
10 directory for a more complete description of module sections.
12 The short summary is that you can use a "load-balance" section in
13 any place where a module name may be used. The semantics of the
14 "load-balance" section are that one of the modules in the section will
15 be chosen at random, evenly spread over the modules in the list.
27 In this case, 1/3 of the RADIUS requests will be processed by
28 "sql1", one third by "sql2", and 1/3 by "sql3".
30 The "load-balance" section can be nested in a "redundant" section,
34 load-balance { # between two redundant sections below
46 This says "load balance between sql1 and sql2, but if sql1 is down,
47 use sql2, and if sql2 is down, use sql1". That way, you can guarantee
48 both that load balancing occurs, and that the requests are *always*
49 logged to one of the databases::
61 This says "load balance between sql1 and sql2, but if the one being
62 used is down, then log to detail".
67 redundant { # between load-balance & detail
68 load-balance { # between two redundant sections
82 This says "try to load balance between sql1 and sql2; if sql1 is down,
83 use sql2; if sql2 is down use sql1; if both sql1 and sql2 are down,
84 then log to the detail file"
87 More complicated scenarios
88 --------------------------
90 If you want to do redundancy and load-balancing among three
91 modules, the configuration is quite complex::
135 For four or more modules, it quickly becomes unmanageable.
137 The solution is to use the "redundant-load-balance" section, which
138 combines the features of "load-balance", with "redundant" fail-over
139 between members. The above complex configuration for three modules
142 redundant-load-balance {
149 Which means "load-balance evenly among all three servers. If the
150 one picked for load-balancing is down, load-balance among the
151 remaining two. If that one is down, pick the one remaining 'live'
154 The "redundant-load-balance" section can contain any number of
158 Interaction with "if" and "else"
159 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
161 It's best to have "if" and "else" blocks contain "load-balance" or
162 "redundant-load-balance" sections, rather than the other way around.
163 The "else" and "elsif" sections cannot appear inside of a
164 "load-balance" or "redundant-load-balance" section, because the "else"
165 condition would be chose as one of the modules for load-balancing,
166 which is not what you want.
168 It's OK to have a plain "if" block inside of a "load-balance" or
169 "redundant-load-balance" section. In that case, the "if" condition
170 checks the return code of the module or group that executed just
171 before the "load-balance" section. It does *not* check the return
172 code of the previous module in the section.