Restrict SSR to paths in the sitemap

Because Angular SSR is not very efficient, after discussion with
the Google Scholar team we realized a compromise would be to only
use SSR for pages in the DSpace sitemap (and the home page).

config/config.example.yml

@@ -23,6 +23,8 @@ ssr:
   # Determining which styles are critical is a relatively expensive operation; this option is
   # disabled (false) by default to boost server performance at the expense of loading smoothness.
   inlineCriticalCss: false
+  # Path prefixes to enable SSR for. By default these are limited to paths of primary DSpace objects.
+  paths: [ '/home', '/items/', '/entities/', '/collections/', '/communities/', '/bitstream/', '/bitstreams/' ]
 
 # The REST API server settings
 # NOTE: these settings define which (publicly available) REST API to use. They are usually

server.ts

@@ -218,7 +218,7 @@ export function app() {
  * The callback function to serve server side angular
  */
 function ngApp(req, res, next) {
-  if (environment.ssr.enabled) {
+  if (environment.ssr.enabled && req.method === 'GET' && (req.path === '/' || environment.ssr.paths.some(pathPrefix => req.path.startsWith(pathPrefix)))) {
     // Render the page to user via SSR (server side rendering)
     serverSideRender(req, res, next);
   } else {

src/config/ssr-config.interface.ts

@@ -20,4 +20,9 @@ export interface SSRConfig extends Config {
    * For improved SSR performance, DSpace defaults this to false (disabled).
    */
   inlineCriticalCss: boolean;
+
+  /**
+   * Paths to enable SSR for. Defaults to the home page and paths in the sitemap.
+   */
+  paths: Array<string>;
 }

src/environments/environment.production.ts

@@ -8,5 +8,6 @@ export const environment: Partial<BuildConfig> = {
     enabled: true,
     enablePerformanceProfiler: false,
     inlineCriticalCss: false,
+    paths: [ '/home', '/items/', '/entities/', '/collections/', '/communities/', '/bitstream/', '/bitstreams/' ],
   },
 };

src/environments/environment.test.ts

@@ -12,6 +12,7 @@ export const environment: BuildConfig = {
     enabled: true,
     enablePerformanceProfiler: false,
     inlineCriticalCss: false,
+    paths: [ '/home', '/items/', '/entities/', '/collections/', '/communities/', '/bitstream/', '/bitstreams/' ],
   },
 
   // Angular express server settings.

src/environments/environment.ts

@@ -13,6 +13,7 @@ export const environment: Partial<BuildConfig> = {
     enabled: false,
     enablePerformanceProfiler: false,
     inlineCriticalCss: false,
+    paths: [ '/home', '/items/', '/entities/', '/collections/', '/communities/', '/bitstream/', '/bitstreams/' ],
   },
 };