[MEDIUM] support setting a server weight to zero

Sometimes it is useful to be able to set a server's weight to zero.
It allows the server to receive only persistent traffic but never
normal traffic.

diff --git a/doc/configuration.txt b/doc/configuration.txt
index cf30c15e387a86cdafa5f3eb09bd1157fb8dcada..89525e8228ea22a5928a34eb43925acb3f5f2bca 100644 (file)
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -4476,11 +4476,12 @@ weight <weight>
   The "weight" parameter is used to adjust the server's weight relative to
   other servers. All servers will receive a load proportional to their weight
   relative to the sum of all weights, so the higher the weight, the higher the
-  load. The default weight is 1, and the maximal value is 255. If this
-  parameter is used to distribute the load according to server's capacity, it
-  is recommended to start with values which can both grow and shrink, for
-  instance between 10 and 100 to leave enough room above and below for later
-  adjustments.
+  load. The default weight is 1, and the maximal value is 256. A value of 0
+  means the server will not participate in load-balancing but will still accept
+  persistent connections. If this parameter is used to distribute the load
+  according to server's capacity, it is recommended to start with values which
+  can both grow and shrink, for instance between 10 and 100 to leave enough
+  room above and below for later adjustments.
 
 
 6. HTTP header manipulation

diff --git a/src/backend.c b/src/backend.c
index 58de35e54cfc9feb18a4a419b870e89dae40575b..5cea8089bdd33ca987f2325a8daf591145f732c7 100644 (file)
--- a/src/backend.c
+++ b/src/backend.c
@@ -203,7 +203,8 @@ void recalc_server_map(struct proxy *px)
                int max = 0;
                best = NULL;
                for (cur = px->srv; cur; cur = cur->next) {
-                       if (flag == (cur->state &
+                       if (cur->eweight &&
+                           flag == (cur->state &
                                     (SRV_RUNNING | SRV_GOINGDOWN | SRV_BACKUP))) {
                                int v;
 
@@ -250,15 +251,24 @@ void init_server_map(struct proxy *p)
                return;
 
        /* We will factor the weights to reduce the table,
-        * using Euclide's largest common divisor algorithm
+        * using Euclide's largest common divisor algorithm.
+        * Since we may have zero weights, we have to first
+        * find a non-zero weight server.
         */
-       pgcd = p->srv->uweight;
-       for (srv = p->srv->next; srv && pgcd > 1; srv = srv->next) {
-               int w = srv->uweight;
-               while (w) {
-                       int t = pgcd % w;
-                       pgcd = w;
-                       w = t;
+       pgcd = 1;
+       srv = p->srv;
+       while (srv && !srv->uweight)
+               srv = srv->next;
+
+       if (srv) {
+               pgcd = srv->uweight; /* note: cannot be zero */
+               while (pgcd > 1 && (srv = srv->next)) {
+                       int w = srv->uweight;
+                       while (w) {
+                               int t = pgcd % w;
+                               pgcd = w;
+                               w = t;
+                       }
                }
        }
 
@@ -283,6 +293,9 @@ void init_server_map(struct proxy *p)
        if (act < bck)
                act = bck;
 
+       if (!act)
+               act = 1;
+
        p->lbprm.map.srv = (struct server **)calloc(act, sizeof(struct server *));
        /* recounts servers and their weights */
        p->lbprm.map.state = PR_MAP_RECALC;

diff --git a/src/cfgparse.c b/src/cfgparse.c
index 413aeaef3eccfa8f928bf2c8c581d07f765dea76..6c0065145c3b494e8d3a61ab7346ba5dcf095017 100644 (file)
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -2185,8 +2185,8 @@ int cfg_parse_listen(const char *file, int linenum, char **args, int kwm)
                        else if (!strcmp(args[cur_arg], "weight")) {
                                int w;
                                w = atol(args[cur_arg + 1]);
-                               if (w < 1 || w > 256) {
-                                       Alert("parsing [%s:%d] : weight of server %s is not within 1 and 256 (%d).\n",
+                               if (w < 0 || w > 256) {
+                                       Alert("parsing [%s:%d] : weight of server %s is not within 0 and 256 (%d).\n",
                                              file, linenum, newsrv->id, w);
                                        return -1;
                                }