From dff277ac0350a28fa0b4af6a929445aae4f73de5 Mon Sep 17 00:00:00 2001
From: aland <aland>
Date: Mon, 14 May 2007 09:42:51 +0000
Subject: [PATCH] 	Use "currently_outstanding" metric for load-balance. 
 i.e. we choose 	the home server with the lowest
 "currently_outstanding" number. 	If there are multiple home servers
 with the same number, randomly 	choose among them.

	This means that when a home server is dead and doesn't respond,
	the requests will immediately be load-balanced to any live servers
---
 src/main/realms.c | 52 +++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 43 insertions(+), 9 deletions(-)

diff --git a/src/main/realms.c b/src/main/realms.c
index 42edf62..54e7cee 100644
--- a/src/main/realms.c
+++ b/src/main/realms.c
@@ -1030,6 +1030,7 @@ home_server *home_server_ldb(const char *realmname,
 {
 	int		start;
 	int		count;
+	home_server	*found = NULL;
 
 	start = 0;
 
@@ -1040,14 +1041,6 @@ home_server *home_server_ldb(const char *realmname,
 		uint32_t hash;
 
 		/*
-		 *	Load balancing.  Pick one at random.
-		 */
-	case HOME_POOL_LOAD_BALANCE:
-		hash = lrad_rand();
-		start = hash % pool->num_home_servers;
-		break;
-
-		/*
 		 *	For load-balancing by client IP address, we
 		 *	pick a home server by hashing the client IP.
 		 *
@@ -1072,6 +1065,9 @@ home_server *home_server_ldb(const char *realmname,
 		start = hash % pool->num_home_servers;
 		break;
 
+	case HOME_POOL_LOAD_BALANCE:
+		found = pool->servers[0];
+
 	default:
 		start = 0;
 		break;
@@ -1098,9 +1094,47 @@ home_server *home_server_ldb(const char *realmname,
 			continue;
 		}
 
-		return home;
+		if (pool->type != HOME_POOL_LOAD_BALANCE) {
+			return home;
+		}
+
+		DEBUG3("PROXY %s %d\t%s %d",
+		       found->name, found->currently_outstanding,
+		       home->name, home->currently_outstanding);
+
+		/*
+		 *	Prefer this server if it's less busy than the
+		 *	one we previously found.
+		 */
+		if (home->currently_outstanding < found->currently_outstanding) {
+			DEBUG3("Choosing %s: It's less busy than %s",
+			       home->name, found->name);
+			found = home;
+			continue;
+		}
+
+		/*
+		 *	Ignore servers which are busier than the one
+		 *	we found.
+		 */
+		if (home->currently_outstanding > found->currently_outstanding) {
+			DEBUG3("Skipping %s: It's busier than %s",
+			       home->name, found->name);
+			continue;
+		}
+
+		/*
+		 *	From the list of servers which have the same
+		 *	load, choose one at random.
+		 */
+		if (((count + 1) * (lrad_rand() & 0xffff)) < (uint32_t) 0x10000) {
+			found = home;
+		}
+
 	} /* loop over the home servers */
 
+	if (found) return found;
+
 	/*
 	 *	No live match found, and no fallback to the "DEFAULT"
 	 *	realm.  We fix this by blindly marking all servers as
-- 
2.1.4