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/*
* sticky load-balancing
*
* Copyright 2024 HAProxy Technologies
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <haproxy/api.h>
#include <haproxy/backend.h>
#include <haproxy/lb_ss.h>
#include <haproxy/server-t.h>
/* this function updates the stick server according to server <srv>'s new state.
*
* The server's lock must be held. The lbprm's lock will be used.
*/
static void ss_set_server_status_down(struct server *srv)
{
struct proxy *p = srv->proxy;
if (!srv_lb_status_changed(srv))
return;
if (srv_willbe_usable(srv))
goto out_update_state;
HA_RWLOCK_WRLOCK(LBPRM_LOCK, &p->lbprm.lock);
if (!srv_currently_usable(srv))
/* server was already down */
goto out_update_backend;
if (srv->flags & SRV_F_BACKUP) {
p->lbprm.tot_wbck -= srv->cur_eweight;
p->srv_bck--;
} else {
p->lbprm.tot_wact -= srv->cur_eweight;
p->srv_act--;
}
if (srv == p->lbprm.ss.srv) {
/* sticked server is down, elect a new server
* that we will be sticking on.
*/
recalc_server_ss(p);
}
out_update_backend:
/* check/update tot_used, tot_weight */
update_backend_weight(p);
HA_RWLOCK_WRUNLOCK(LBPRM_LOCK, &p->lbprm.lock);
out_update_state:
srv_lb_commit_status(srv);
}
/* This function updates the stick server according to server <srv>'s new state.
*
* The server's lock must be held. The lbprm's lock will be used.
*/
static void ss_set_server_status_up(struct server *srv)
{
struct proxy *p = srv->proxy;
if (!srv_lb_status_changed(srv))
return;
if (!srv_willbe_usable(srv))
goto out_update_state;
HA_RWLOCK_WRLOCK(LBPRM_LOCK, &p->lbprm.lock);
if (srv_currently_usable(srv))
/* server was already up */
goto out_update_backend;
if (srv->flags & SRV_F_BACKUP) {
p->lbprm.tot_wbck += srv->next_eweight;
p->srv_bck++;
} else {
p->lbprm.tot_wact += srv->next_eweight;
p->srv_act++;
}
if (!p->lbprm.ss.srv ||
((p->lbprm.ss.srv->flags & SRV_F_BACKUP) && !(srv->flags & SRV_F_BACKUP))) {
/* we didn't have a server or were sticking on a backup server,
* but now we have an active server, let's switch to it
*/
p->lbprm.ss.srv = srv;
}
out_update_backend:
/* check/update tot_used, tot_weight */
update_backend_weight(p);
HA_RWLOCK_WRUNLOCK(LBPRM_LOCK, &p->lbprm.lock);
out_update_state:
srv_lb_commit_status(srv);
}
/* This function elects a new stick server for proxy px.
*
* The lbprm's lock must be held.
*/
void recalc_server_ss(struct proxy *px)
{
struct server *cur, *first;
int flag;
if (!px->lbprm.tot_used)
return; /* no server */
/* here we *know* that we have some servers */
if (px->srv_act)
flag = 0;
else
flag = SRV_F_BACKUP;
first = NULL;
for (cur = px->srv; cur; cur = cur->next) {
if ((cur->flags & SRV_F_BACKUP) == flag &&
srv_willbe_usable(cur)) {
first = cur;
break;
}
}
px->lbprm.ss.srv = first;
}
/* This function is responsible for preparing sticky LB algorithm.
* It should be called only once per proxy, at config time.
*/
void init_server_ss(struct proxy *p)
{
struct server *srv;
p->lbprm.set_server_status_up = ss_set_server_status_up;
p->lbprm.set_server_status_down = ss_set_server_status_down;
p->lbprm.update_server_eweight = NULL;
if (!p->srv)
return;
for (srv = p->srv; srv; srv = srv->next) {
srv->next_eweight = 1; /* ignore weights, all servers have the same weight */
srv_lb_commit_status(srv);
}
/* recounts servers and their weights */
recount_servers(p);
update_backend_weight(p);
recalc_server_ss(p);
}
/*
* This function returns the server that we're sticking on. If any server
* is found, it will be returned. If no valid server is found, NULL is
* returned.
*
* The lbprm's lock will be used.
*/
struct server *ss_get_server(struct proxy *px)
{
struct server *srv = NULL;
HA_RWLOCK_RDLOCK(LBPRM_LOCK, &px->lbprm.lock);
srv = px->lbprm.ss.srv;
HA_RWLOCK_RDUNLOCK(LBPRM_LOCK, &px->lbprm.lock);
return srv;
}
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