Adds configurable ajax connection queueing.

Fixes bug 965910.

Change-Id: I84807f6ca0d9769d25b942c151c1a83501648a0a

horizon/context_processors.py

@@ -51,7 +51,8 @@ def horizon(request):
         for each template/template fragment which takes context that is used
         to render the complete output.
     """
-    context = {"True": True,
+    context = {"HORIZON_CONFIG": getattr(settings, "HORIZON_CONFIG", {}),
+               "True": True,
                "False": False}
 
     # Auth/Keystone context

horizon/static/horizon/js/horizon.js

@@ -101,7 +101,8 @@ var Horizon = function() {
         $rows_to_update.each(function(index, row) {
           var $row = $(this),
               $table = $row.closest('table');
-          $.ajax($row.attr('data-update-url'), {
+          horizon.ajax.queue({
+            url: $row.attr('data-update-url'),
             error: function (jqXHR, textStatus, errorThrown) {
               switch (jqXHR.status) {
                 // A 404 indicates the object is gone, and should be removed from the table
@@ -276,6 +277,55 @@ var Horizon = function() {
     return $(template.render(params)).prependTo("#main_content .messages");
   };
 
+  /* Queued ajax handling for Horizon.
+   *
+   * Note: The number of concurrent AJAX connections hanlded in the queue
+   * can be configured by setting an "ajax_queue_limit" key in
+   * settings.HORIZON_CONFIG to the desired number (or None to disable queue
+   * limiting).
+   */
+  horizon.ajax = {
+    // This will be our jQuery queue container.
+    _queue: [],
+    _active: [],
+    // Function to add a new call to the queue.
+    queue: function(opts) {
+      var complete = opts.complete,
+          active = horizon.ajax._active;
+
+      opts.complete = function () {
+        var index = $.inArray(request, active);
+        if (index > -1) {
+          active.splice(index, 1);
+        }
+        horizon.ajax.next();
+        if (complete) {
+          complete.apply(this, arguments);
+        }
+      };
+
+      function request() {
+        return $.ajax(opts);
+      }
+
+      // Queue the request
+      horizon.ajax._queue.push(request);
+
+      // Start up the queue handler in case it's stopped.
+      horizon.ajax.next();
+    },
+    next: function () {
+      var queue = horizon.ajax._queue,
+          limit = horizon.conf.ajax.queue_limit,
+          request;
+      if (queue.length && (!limit || horizon.ajax._active.length < limit)) {
+        request = queue.pop();
+        horizon.ajax._active.push(request);
+        return request();
+      }
+    }
+  };
+
   return horizon;
 };
 

horizon/templates/horizon/client_side/conf.html

@@ -4,6 +4,9 @@
  */
 horizon.conf = {
     debug: {{ debug|yesno:"true,false" }},
-    static_url: "{{ STATIC_URL }}"
+    static_url: "{{ STATIC_URL }}",
+    ajax: {
+        queue_limit: {{ HORIZON_CONFIG.ajax_queue_limit|default:"null" }}
+    }
 }
 </script>

openstack_dashboard/settings.py

@@ -52,6 +52,7 @@ HORIZON_CONFIG = {
     'dashboards': ('nova', 'syspanel', 'settings',),
     'default_dashboard': 'nova',
     'user_home': 'openstack_dashboard.views.user_home',
+    'ajax_queue_limit': 10
 }
 
 MIDDLEWARE_CLASSES = (