MINOR: backend: implement random-based load balancing
For large farms where servers are regularly added or removed, picking
a random server from the pool can ensure faster load transitions than
when using round-robin and less traffic surges on the newly added
servers than when using leastconn.
This commit introduces "balance random". It internally uses a random as
the key to the consistent hashing mechanism, thus all features available
in consistent hashing such as weights and bounded load via hash-balance-
factor are usable. It is extremely convenient because one common concern
when using random is what happens when a server is hammered a bit too
much. Here that can trivially be avoided, like in the configuration below :
backend bk0
balance random
hash-balance-factor 110
server-template s 1-100 127.0.0.1:8000 check inter 1s
Note that while "balance random" internally relies on a hash algorithm,
it holds the same properties as round-robin and as such is compatible with
reusing an existing server connection with "option prefer-last-server".
diff --git a/src/cfgparse.c b/src/cfgparse.c
index 7653536..024502c 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -8350,6 +8350,9 @@
if ((curproxy->lbprm.algo & BE_LB_PARM) == BE_LB_RR_STATIC) {
curproxy->lbprm.algo |= BE_LB_LKUP_MAP;
init_server_map(curproxy);
+ } else if ((curproxy->lbprm.algo & BE_LB_PARM) == BE_LB_RR_RANDOM) {
+ curproxy->lbprm.algo |= BE_LB_LKUP_CHTREE | BE_LB_PROP_DYN;
+ chash_init_server_tree(curproxy);
} else {
curproxy->lbprm.algo |= BE_LB_LKUP_RRTREE | BE_LB_PROP_DYN;
fwrr_init_server_groups(curproxy);