MEDIUM: lb_fwrr: Don't start all thread groups on the same server.

Now that all there is one tree per thread group, all thread groups will
start on the same server. To prevent that, just insert the servers in a
different order for each thread group.

Author: Olivier Houchard

src/lb_fwrr.c

@@ -297,7 +297,7 @@ void fwrr_init_server_groups(struct proxy *p)
 {
 	struct server *srv;
 	struct eb_root init_head = EB_ROOT;
-	int i;
+	int i, j;
 
 	p->lbprm.set_server_status_up   = fwrr_set_server_status_up;
 	p->lbprm.set_server_status_down = fwrr_set_server_status_down;
@@ -334,7 +334,21 @@ void fwrr_init_server_groups(struct proxy *p)
 		p->per_tgrp[i].lbprm.fwrr.bck.next = &p->per_tgrp[i].lbprm.fwrr.bck.t1;
 
 		/* queue active and backup servers in two distinct groups */
+		j = 0;
 		for (srv = p->srv; srv; srv = srv->next) {
+			j++;
+			if (!srv_currently_usable(srv))
+				continue;
+			if (j <= i)
+				continue;
+			fwrr_queue_by_weight((srv->flags & SRV_F_BACKUP) ?
+					p->per_tgrp[i].lbprm.fwrr.bck.init :
+					p->per_tgrp[i].lbprm.fwrr.act.init,
+					srv, i + 1);
+		}
+		j = 0;
+		for (srv = p->srv; srv && j < i; srv = srv->next) {
+			j++;
 			if (!srv_currently_usable(srv))
 				continue;
 			fwrr_queue_by_weight((srv->flags & SRV_F_BACKUP) ?