MINOR: backend: add hash-balance-factor option for hash-type consistent
0 will mean no balancing occurs; otherwise it represents the ratio
between the highest-loaded server and the average load, times 100 (i.e.
a value of 150 means a 1.5x ratio), assuming equal weights.
Signed-off-by: Andrew Rodland <andrewr@vimeo.com>
diff --git a/doc/configuration.txt b/doc/configuration.txt
index d047524..a93c103 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -2205,6 +2205,32 @@
See also : "dispatch", "cookie", "transparent", "hash-type" and "http_proxy".
+balance-factor <factor>
+ Specify the balancing factor for bounded-load consistent hashing
+ May be used in sections : defaults | frontend | listen | backend
+ yes | no | no | yes
+ Arguments :
+ <factor> is the control for the maximum number of concurrent requests to
+ send to a server, expressed as a percentage of the average number
+ of concurrent requests across all of the active servers.
+
+ Specifying a "balance-factor" for a server with "hash-type consistent"
+ enables an algorithm that prevents any one server from getting too many
+ requests at once, even if some hash buckets receive many more requests than
+ others. Setting <factor> to 0 (the default) disables the feature. Otherwise,
+ <factor> is a percentage greater than 100. For example, if <factor> is 150,
+ then no server will be allowed to have a load more than 1.5 times the average.
+ If server weights are used, they will be respected.
+
+ If the first-choice server is disqualified, the algorithm will choose another
+ server based on the request hash, until a server with additional capacity is
+ found. A higher <factor> allows more imbalance between the servers, while a
+ lower <factor> means that more servers will be checked on average, affecting
+ performance. Reasonable values are from 125 to 200.
+
+ See also : "balance" and "hash-type".
+
+
bind [<address>]:<port_range> [, ...] [param*]
bind /<path> [, ...] [param*]
Define one or several listening addresses and/or ports in a frontend.
@@ -3358,7 +3384,7 @@
default function is "sdbm", the selection of a function should be based on
the range of the values being hashed.
- See also : "balance", "server"
+ See also : "balance", "balance-factor", "server"
http-check disable-on-404
diff --git a/include/types/lb_chash.h b/include/types/lb_chash.h
index 5991ce9..b711636 100644
--- a/include/types/lb_chash.h
+++ b/include/types/lb_chash.h
@@ -30,6 +30,7 @@
struct eb_root act; /* weighted chash entries of active servers */
struct eb_root bck; /* weighted chash entries of backup servers */
struct eb32_node *last; /* last node found in case of round robin (or NULL) */
+ int balance_factor; /* load balancing factor * 100, 0 if disabled */
};
#endif /* _TYPES_LB_CHASH_H */
diff --git a/src/cfgparse.c b/src/cfgparse.c
index cc2f507..229b3ce 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -1983,6 +1983,7 @@
defproxy.maxconn = cfg_maxpconn;
defproxy.conn_retries = CONN_RETRIES;
defproxy.redispatch_after = 0;
+ defproxy.lbprm.chash.balance_factor = 0;
defproxy.defsrv.check.inter = DEF_CHKINTR;
defproxy.defsrv.check.fastinter = 0;
@@ -2825,6 +2826,7 @@
if (curproxy->cap & PR_CAP_BE) {
curproxy->lbprm.algo = defproxy.lbprm.algo;
+ curproxy->lbprm.chash.balance_factor = defproxy.lbprm.chash.balance_factor;
curproxy->fullconn = defproxy.fullconn;
curproxy->conn_retries = defproxy.conn_retries;
curproxy->redispatch_after = defproxy.redispatch_after;
@@ -5958,6 +5960,19 @@
}
}
}
+ else if (strcmp(args[0], "hash-balance-factor") == 0) {
+ if (*(args[1]) == 0) {
+ Alert("parsing [%s:%d] : '%s' expects an integer argument.\n", file, linenum, args[0]);
+ err_code |= ERR_ALERT | ERR_FATAL;
+ goto out;
+ }
+ curproxy->lbprm.chash.balance_factor = atol(args[1]);
+ if (curproxy->lbprm.chash.balance_factor != 0 && curproxy->lbprm.chash.balance_factor <= 100) {
+ Alert("parsing [%s:%d] : '%s' must be 0 or greater than 100.\n", file, linenum, args[0]);
+ err_code |= ERR_ALERT | ERR_FATAL;
+ goto out;
+ }
+ }
else if (strcmp(args[0], "unique-id-format") == 0) {
if (!*(args[1])) {
Alert("parsing [%s:%d] : %s expects an argument.\n", file, linenum, args[0]);