From: willy tarreau <willy@wtap.(none)>
Date: Wed, 12 Apr 2006 18:29:08 +0000 (+0200)
Subject: [MEDIUM] now the round-robin load balancer uses two passes to avoid saturated servers... 
X-Git-Tag: v1.2.13~28
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=898db9d5958a18c48d188d9fcdbd0d8b148386e5;p=thirdparty%2Fhaproxy.git

[MEDIUM] now the round-robin load balancer uses two passes to avoid saturated servers. The first avoids servers which have filled with maxconn connections, and a second pass can enforce the selection of one of them if the first pass found no candidate.
---

diff --git a/haproxy.c b/haproxy.c
index d4953ac4f3..1eb714e70b 100644
--- a/haproxy.c
+++ b/haproxy.c
@@ -1972,10 +1972,40 @@ static void recalc_server_map(struct proxy *px) {
     px->srv_map_sz = tot;
 }
 
+/*
+ * This function tries to find a running server with free connection slots for
+ * the proxy <px> following the round-robin method.
+ * If any server is found, it will be returned and px->srv_rr_idx will be updated
+ * to point to the next server. If no valid server is found, NULL is returned.
+ */
+static inline struct server *get_server_rr_with_conns(struct proxy *px) {
+    int newidx;
+    struct server *srv;
+
+    if (px->srv_map_sz == 0)
+	return NULL;
+
+    if (px->srv_rr_idx < 0 || px->srv_rr_idx >= px->srv_map_sz)
+	px->srv_rr_idx = 0;
+    newidx = px->srv_rr_idx;
+
+    do {
+	srv = px->srv_map[newidx++];
+	if (!srv->maxconn || srv->cur_sess < srv->maxconn) {
+	    px->srv_rr_idx = newidx;
+	    return srv;
+	}
+	if (newidx == px->srv_map_sz)
+	    newidx = 0;
+    } while (newidx != px->srv_rr_idx);
+
+    return NULL;
+}
+
+
 /*
  * This function tries to find a running server for the proxy <px> following
- * the round-robin method. Depending on the number of active/backup servers,
- * it will either look for active servers, or for backup servers.
+ * the round-robin method.
  * If any server is found, it will be returned and px->srv_rr_idx will be updated
  * to point to the next server. If no valid server is found, NULL is returned.
  */
@@ -2044,7 +2074,9 @@ int connect_server(struct session *s) {
 	if (s->proxy->options & PR_O_BALANCE_RR) {
 	    struct server *srv;
 
-	    srv = get_server_rr(s->proxy);
+	    srv = get_server_rr_with_conns(s->proxy);
+	    if (!srv)
+		srv = get_server_rr(s->proxy);
 	    s->srv_addr = srv->addr;
 	    s->srv = srv;
 	}