Cache invalidate for previews

no issue

- draft updates now need to affect the preview route

core/server/api/index.js

@@ -80,6 +80,8 @@ cacheInvalidationHeader = function (req, result) {
             // Don't set x-cache-invalidate header for drafts
             if (hasStatusChanged || wasDeleted || wasPublishedUpdated) {
                 cacheInvalidate = '/*';
+            } else {
+                cacheInvalidate = '/' + config.routeKeywords.preview + '/' + post.uuid + '/';
             }
         }
     }

core/server/middleware/index.js

@@ -301,8 +301,11 @@ setupMiddleware = function (blogAppInstance, adminApp) {
     blogApp.use(passport.initialize());
 
     // ### Caching
+    // Blog frontend is cacheable
     blogApp.use(middleware.cacheControl('public'));
+    // Admin shouldn't be cached
     adminApp.use(middleware.cacheControl('private'));
+    // API shouldn't be cached
     blogApp.use(routes.apiBaseUri, middleware.cacheControl('private'));
 
     // enable authentication

core/test/functional/routes/api/posts_spec.js

@@ -540,8 +540,8 @@ describe('Post API', function () {
                                 return done(err);
                             }
 
-                            // Updating a draft should not send x-cache-invalidate headers
+                            // Updating a draft should send x-cache-invalidate headers for the preview only
-                            should.not.exist(res.headers['x-cache-invalidate']);
+                            res.headers['x-cache-invalidate'].should.eql('/p/' + draftPost.posts[0].uuid + '/');
                             done();
                         });
                 });