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-rw-r--r--src/lb_ss.c183
1 files changed, 183 insertions, 0 deletions
diff --git a/src/lb_ss.c b/src/lb_ss.c
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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;
+}