[IMP] base,web: Improve webclient startup

Today, some resources that varies very infrequentely are requested on
every page load: the menus, the translations and the qweb templates

After this commit, there will be 2 improvements that will make the
loading of the webclient faster:
1. cache almost static resources forever
when loading the /web/ page, the user session will
contain the cache key to be used to fetch these resources. As the content
of the resource itself it used to compute the hash, the request can be
put in cache by the browser forever (for a year).

The up side is that in general less requests are needed to load the web client
The down side is that the load time and number of queries of /web page
has increased to include what is needed to compute the hash of translations,
menus and qweb templates

2. trigger the loading of the menus before the download (and startup) of
the JS and CSS assets:
The menus contains the definition of the action, wich is the first thing
needed to load a page in odoo. Starting the loading of the menu much
earlier means that when they are not yet in the browser cache (see point 1),
the browser does not need to wait for the entire assets to be downloaded
and parsed before starting the 'load_menu' request, but instead start it
immediately and hold onto a promise to be used instead of the rpc 'load_menu'.

Because the request is done before anything else is loaded, including
JQuery, it is made in vanilla JS.

Co-authored-by: Julien Mougenot <jum@odoo.com>

1 files changed, 13 insertions, 2 deletions

diff --git a/addons/web/static/src/js/core/session.js b/addons/web/static/src/js/core/session.js
index 21103a9529a..e083bb71e7f 100644
--- a/addons/web/static/src/js/core/session.js
+++ b/addons/web/static/src/js/core/session.js
@@ -241,8 +241,11 @@ var Session = core.Class.extend(mixins.EventDispatcherMixin, {
         });
     },
     load_qweb: function (mods) {
+        var self = this;
         var lock = this.qweb_mutex.exec(function () {
-            return $.get('/web/webclient/qweb?mods=' + mods).then(function (doc) {
+            var cacheId = self.cache_hashes && self.cache_hashes.qweb;
+            var route  = '/web/webclient/qweb/' + (cacheId ? cacheId : Date.now()) + '?mods=' + mods;
+            return $.get(route).then(function (doc) {
                 if (!doc) { return; }
                 qweb.add_template(doc);
             });
@@ -344,10 +347,18 @@ var Session = core.Class.extend(mixins.EventDispatcherMixin, {
     getTZOffset: function (date) {
         return -new Date(date).getTimezoneOffset();
     },
-
     //--------------------------------------------------------------------------
     // Public
     //--------------------------------------------------------------------------
+    /**
+     * Replaces the value of a key in cache_hashes (the hash of some resource computed on the back-end by a unique value
+     * @param {string} key the key in the cache_hashes to invalidate
+     */
+    invalidateCacheKey: function(key) {
+        if (this.cache_hashes && this.cache_hashes[key]) {
+            this.cache_hashes[key] = Date.now();
+        }
+    },
 
     /**
      * Reload the currencies (initially given in session_info). This is meant to