[CST-5729] Add possibility to store response's headers into the SSR cache

Author: atarix83

server.ts

@@ -53,7 +53,7 @@ import { buildAppConfig } from './src/config/config.server';
 import { APP_CONFIG, AppConfig } from './src/config/app-config.interface';
 import { extendEnvironmentWithAppConfig } from './src/config/config.util';
 import { logStartupMessage } from './startup-message';
-import { TOKENITEM } from 'src/app/core/auth/models/auth-token-info.model';
+import { TOKENITEM } from './src/app/core/auth/models/auth-token-info.model';
 
 
 /*
@@ -374,9 +374,15 @@ function cacheCheck(req, res, next) {
   }
 
   // If cached copy exists, return it to the user.
-  if (cachedCopy) {
+  if (cachedCopy && cachedCopy.page) {
+    if (cachedCopy.headers && Array.isArray(environment.cache.serverSide.headers) && environment.cache.serverSide.headers.length > 0) {
+      environment.cache.serverSide.headers.forEach((header) => {
+        if (environment.cache.serverSide.debug) { console.log(`Restore cached ${header} header`); }
+        res.setHeader(header, cachedCopy.headers[header.toLowerCase()]);
+      });
+    }
     res.locals.ssr = true;  // mark response as SSR-generated (enables text compression)
-    res.send(cachedCopy);
+    res.send(cachedCopy.page);
 
     // Tell Express to skip all other handlers for this path
     // This ensures we don't try to re-render the page since we've already returned the cached copy
@@ -452,16 +458,18 @@ function saveToCache(req, page: any) {
     // Avoid caching "/reload/[random]" paths (these are hard refreshes after logout)
     if (key.startsWith('/reload')) { return; }
 
+    // Retrieve response headers
+    const headers = req.res.getHeaders();
     // If bot cache is enabled, save it to that cache if it doesn't exist or is expired
     // (NOTE: has() will return false if page is expired in cache)
     if (botCacheEnabled() && !botCache.has(key)) {
-      botCache.set(key, page);
+      botCache.set(key, { page, headers });
       if (environment.cache.serverSide.debug) { console.log(`CACHE SAVE FOR ${key} in bot cache.`); }
     }
 
     // If anonymous cache is enabled, save it to that cache if it doesn't exist or is expired
     if (anonymousCacheEnabled() && !anonymousCache.has(key)) {
-      anonymousCache.set(key, page);
+      anonymousCache.set(key, { page, headers });
       if (environment.cache.serverSide.debug) { console.log(`CACHE SAVE FOR ${key} in anonymous cache.`); }
     }
   }

src/config/cache-config.interface.ts

@@ -13,6 +13,8 @@ export interface CacheConfig extends Config {
   serverSide: {
     // Debug server-side caching.  Set to true to see cache hits/misses/refreshes in console logs.
     debug: boolean,
+    // List of headers to restore from the cache hit
+    headers: string[],
     // Cache specific to known bots.  Allows you to serve cached contents to bots only.
     botCache: {
       // Maximum number of pages (rendered via SSR) to cache. Setting max=0 disables the cache.

src/config/default-app-config.ts

@@ -78,6 +78,8 @@ export class DefaultAppConfig implements AppConfig {
     // In-memory cache of server-side rendered content
     serverSide: {
       debug: false,
+      // Link header is used for signposting functionality
+      headers: ['Link'],
       // Cache specific to known bots.  Allows you to serve cached contents to bots only.
       // Defaults to caching 1,000 pages. Each page expires after 1 day
       botCache: {