Serialize server weighting parameters

The server weighting parameters couldn't be altered online and they
weren't serialized to disk. Only servers that are created online will have
their weighting parameters persisted to disk.

server/core/config_runtime.c

@@ -286,7 +286,20 @@ bool runtime_alter_server(SERVER *server, char *key, char *value)
     }
     else
     {
-        valid = false;
+        if (!serverRemoveParameter(server, key) && !value[0])
+        {
+            valid = false;
+        }
+        else if (value[0])
+        {
+            serverAddParameter(server, key, value);
+
+            /**
+             * It's likely that this parameter is used as a weighting parameter.
+             * We need to update the weights of services that use this.
+             */
+            service_update_weights();
+        }
     }
 
     if (valid)

server/core/maxscale/service.h

@@ -109,6 +109,9 @@ int      service_isvalid(SERVICE *service);
  */
 bool service_server_in_use(const SERVER *server);
 
+/** Update the server weights used by services */
+void service_update_weights();
+
 /**
  * Alteration of the service configuration
  */

server/core/server.c

@@ -545,7 +545,11 @@ dprintServer(DCB *dcb, SERVER *server)
         dcb_printf(dcb, "\tServer Parameters:\n");
         while (param)
         {
-            dcb_printf(dcb, "\t                                       %s\t%s\n", param->name, param->value);
+            if (param->active)
+            {
+                dcb_printf(dcb, "\t                                       %s\t%s\n",
+                           param->name, param->value);
+            }
             param = param->next;
         }
     }
@@ -854,26 +858,48 @@ server_update_credentials(SERVER *server, char *user, char *passwd)
  * @param       name    The parameter name
  * @param       value   The parameter value
  */
-void
-serverAddParameter(SERVER *server, char *name, char *value)
+void serverAddParameter(SERVER *server, const char *name, const char *value)
 {
-    name = MXS_STRDUP(name);
-    value = MXS_STRDUP(value);
+    char *my_name = MXS_STRDUP(name);
+    char *my_value = MXS_STRDUP(value);
 
     SERVER_PARAM *param = (SERVER_PARAM *)MXS_MALLOC(sizeof(SERVER_PARAM));
 
-    if (!name || !value || !param)
+    if (!my_name || !my_value || !param)
     {
-        MXS_FREE(name);
-        MXS_FREE(value);
+        MXS_FREE(my_name);
+        MXS_FREE(my_value);
         MXS_FREE(param);
         return;
     }
 
-    param->name = name;
-    param->value = value;
+    param->active = true;
+    param->name = my_name;
+    param->value = my_value;
+
+    spinlock_acquire(&server->lock);
     param->next = server->parameters;
     server->parameters = param;
+    spinlock_release(&server->lock);
+}
+
+bool serverRemoveParameter(SERVER *server, const char *name)
+{
+    bool rval = false;
+    spinlock_acquire(&server->lock);
+
+    for (SERVER_PARAM *p = server->parameters; p; p = p->next)
+    {
+        if (strcmp(p->name, name) == 0 && p->active)
+        {
+            p->active = false;
+            rval = true;
+            break;
+        }
+    }
+
+    spinlock_release(&server->lock);
+    return rval;
 }
 
 /**
@@ -908,7 +934,7 @@ serverGetParameter(SERVER *server, char *name)
 
     while (param)
     {
-        if (strcmp(param->name, name) == 0)
+        if (strcmp(param->name, name) == 0 && param->active)
         {
             return param->value;
         }
@@ -1142,6 +1168,14 @@ static bool create_server_config(const SERVER *server, const char *filename)
         dprintf(file, "persistmaxtime=%ld\n", server->persistmaxtime);
     }
 
+    for (SERVER_PARAM *p = server->parameters; p; p = p->next)
+    {
+        if (p->active)
+        {
+            dprintf(file, "%s=%s\n", p->name, p->value);
+        }
+    }
+
     if (server->server_ssl)
     {
         dprintf(file, "ssl=required\n");

server/core/service.c

@@ -2271,7 +2271,7 @@ static void service_calculate_weights(SERVICE *service)
 
                     if (perc == 0)
                     {
-                        MXS_ERROR("Weighting parameter '%s' with a value of %d for"
+                        MXS_WARNING("Weighting parameter '%s' with a value of %d for"
                                   " server '%s' rounds down to zero with total weight"
                                   " of %d for service '%s'. No queries will be "
                                   "routed to this server as long as a server with"
@@ -2300,6 +2300,18 @@ static void service_calculate_weights(SERVICE *service)
     }
 }
 
+void service_update_weights()
+{
+    spinlock_acquire(&service_spin);
+
+    for (SERVICE *service = allServices; service; service = service->next)
+    {
+        service_calculate_weights(service);
+    }
+
+    spinlock_release(&service_spin);
+}
+
 bool service_server_in_use(const SERVER *server)
 {
     bool rval = false;