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[MEDIUM] backend: introduce the "static-rr" LB algorithm

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The "static-rr" is just the old round-robin algorithm. It is still
in use when a hash algorithm is used and the data to hash is not
present, but it was impossible to configure it explicitly. This one
is cheaper in terms of CPU and supports unlimited numbers of servers,
so it makes sense to be able to use it.
This commit is contained in:
Willy Tarreau 2009-10-03 12:56:50 +02:00
parent da76f4f711
commit 9757a38feb
4 changed files with 38 additions and 5 deletions
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18
doc/configuration.txt
View File

@ -915,7 +915,23 @@ balance url_param <param> [check_post [<max_wait>]]
This is the smoothest and fairest algorithm when the server's
processing time remains equally distributed. This algorithm
is dynamic, which means that server weights may be adjusted
on the fly for slow starts for instance.
on the fly for slow starts for instance. It is limited by
design to 4128 active servers per backend. Note that in some
large farms, when a server becomes up after having been down
for a very short time, it may sometimes take a few hundreds
requests for it to be re-integrated into the farm and start
receiving traffic. This is normal, though very rare. It is
indicated here in case you would have the chance to observe
it, so that you don't worry.
static-rr Each server is used in turns, according to their weights.
This algorithm is as similar to roundrobin except that it is
static, which means that changing a server's weight on the
fly will have no effect. On the other hand, it has no design
limitation on the number of servers, and when a server goes
up, it is always immediately reintroduced into the farm, once
the full map is recomputed. It also uses slightly less CPU to
run (around -1%).
leastconn The server with the lowest number of connections receives the
connection. Round-robin is performed within groups of servers

4
include/types/backend.h
View File

@ -42,6 +42,9 @@
#define BE_LB_HASH_PRM 0x00002 /* hash HTTP URL parameter */
#define BE_LB_HASH_HDR 0x00003 /* hash HTTP header value */
#define BE_LB_HASH_RDP 0x00004 /* hash RDP cookie value */
#define BE_LB_RR_DYN 0x00000 /* dynamic round robin (default) */
#define BE_LB_RR_STATIC 0x00001 /* static round robin */
#define BE_LB_PARM 0x000FF /* mask to get/clear the LB param */
/* Required input(s) */
@ -65,6 +68,7 @@
#define BE_LB_ALGO_NONE (BE_LB_KIND_NONE | BE_LB_NEED_NONE) /* not defined */
#define BE_LB_ALGO_RR (BE_LB_KIND_RR | BE_LB_NEED_NONE) /* round robin */
#define BE_LB_ALGO_LC (BE_LB_KIND_LC | BE_LB_NEED_NONE) /* least connections */
#define BE_LB_ALGO_SRR (BE_LB_KIND_RR | BE_LB_NEED_NONE | BE_LB_RR_STATIC) /* static round robin */
#define BE_LB_ALGO_SH (BE_LB_KIND_HI | BE_LB_NEED_ADDR | BE_LB_HASH_SRC) /* hash: source IP */
#define BE_LB_ALGO_UH (BE_LB_KIND_HI | BE_LB_NEED_HTTP | BE_LB_HASH_URI) /* hash: HTTP URI */
#define BE_LB_ALGO_PH (BE_LB_KIND_HI | BE_LB_NEED_HTTP | BE_LB_HASH_PRM) /* hash: HTTP URL parameter */

12
src/backend.c
View File

@ -516,7 +516,11 @@ int assign_server(struct session *s)
break;
case BE_LB_LKUP_MAP:
if ((s->be->lbprm.algo & BE_LB_KIND) != BE_LB_KIND_HI) {
if ((s->be->lbprm.algo & BE_LB_KIND) == BE_LB_KIND_RR) {
s->srv = map_get_server_rr(s->be, s->prev_srv);
break;
}
else if ((s->be->lbprm.algo & BE_LB_KIND) != BE_LB_KIND_HI) {
/* unknown balancing algorithm */
err = SRV_STATUS_INTERNAL;
goto out;
@ -973,6 +977,10 @@ int backend_parse_balance(const char **args, char *err, int errlen, struct proxy
curproxy->lbprm.algo &= ~BE_LB_ALGO;
curproxy->lbprm.algo |= BE_LB_ALGO_RR;
}
else if (!strcmp(args[0], "static-rr")) {
curproxy->lbprm.algo &= ~BE_LB_ALGO;
curproxy->lbprm.algo |= BE_LB_ALGO_SRR;
}
else if (!strcmp(args[0], "leastconn")) {
curproxy->lbprm.algo &= ~BE_LB_ALGO;
curproxy->lbprm.algo |= BE_LB_ALGO_LC;
@ -1098,7 +1106,7 @@ int backend_parse_balance(const char **args, char *err, int errlen, struct proxy
}
}
else {
snprintf(err, errlen, "'balance' only supports 'roundrobin', 'leastconn', 'source', 'uri', 'url_param', 'hdr(name)' and 'rdp-cookie(name)' options.");
snprintf(err, errlen, "'balance' only supports 'roundrobin', 'static-rr', 'leastconn', 'source', 'uri', 'url_param', 'hdr(name)' and 'rdp-cookie(name)' options.");
return -1;
}
return 0;

9
src/cfgparse.c
View File

@ -4196,8 +4196,13 @@ int check_config_validity()
curproxy->lbprm.algo &= ~(BE_LB_LKUP | BE_LB_PROP_DYN);
switch (curproxy->lbprm.algo & BE_LB_KIND) {
case BE_LB_KIND_RR:
curproxy->lbprm.algo |= BE_LB_LKUP_RRTREE | BE_LB_PROP_DYN;
fwrr_init_server_groups(curproxy);
if ((curproxy->lbprm.algo & BE_LB_PARM) == BE_LB_RR_STATIC) {
curproxy->lbprm.algo |= BE_LB_LKUP_MAP;
init_server_map(curproxy);
} else {
curproxy->lbprm.algo |= BE_LB_LKUP_RRTREE | BE_LB_PROP_DYN;
fwrr_init_server_groups(curproxy);
}
break;
case BE_LB_KIND_LC:
curproxy->lbprm.algo |= BE_LB_LKUP_LCTREE | BE_LB_PROP_DYN;