PYIC-7910 Preload templates for all pages

browser-tests/Dockerfile

@@ -12,6 +12,6 @@ COPY ./browser-tests/snapshot-tests ./snapshot-tests
 COPY ./browser-tests/playwright.config.ts ./
 COPY ./browser-tests/tsconfig.json ./
 COPY ../views/ipv/page ../views/ipv/page
-COPY ../src/test-utils/pages-and-contexts.ts ../src/test-utils/pages-and-contexts.ts
+COPY ../src/config/pages-and-contexts.ts ../src/config/pages-and-contexts.ts
 
 CMD ["npm run test"]

browser-tests/data/pagesAndContexts.ts

@@ -1,4 +1,4 @@
-import {pagesAndContexts} from "../../src/test-utils/pages-and-contexts";
+import {pagesAndContexts} from "../../src/config/pages-and-contexts";
 
 type TestFn = (pageName: string, context: string | undefined, language: string, url: string) => void;
 

browser-tests/snapshot-tests/snapshot.spec.ts

@@ -4,7 +4,7 @@ import fs from "fs";
 import {
   iteratePagesAndContexts
 } from "../data/pagesAndContexts";
-import { pagesAndContexts } from "../../src/test-utils/pages-and-contexts";
+import { pagesAndContexts } from "../../src/config/pages-and-contexts";
 
 test.describe.parallel("Snapshot tests", () => {
   test.setTimeout(120000);

src/app.ts

@@ -19,7 +19,7 @@ import config from "./config/config";
 import { setLocals } from "./lib/locals";
 import { loggerMiddleware, logger } from "./lib/logger";
 import { i18nextConfigurationOptions } from "./config/i18next";
-import { configureNunjucks } from "./config/nunjucks";
+import { configureNunjucks, preloadTemplates } from "./config/nunjucks";
 import serverErrorHandler from "./handlers/internal-server-error-handler";
 import journeyEventErrorHandler from "./handlers/journey-event-error-handler";
 import pageNotFoundHandler from "./handlers/page-not-found-handler";
@@ -110,7 +110,9 @@ app.get("/healthcheck", (req, res) => {
 
 app.use(setLocals);
 app.use(cspHandler);
-app.set("view engine", configureNunjucks(app, APP_VIEWS));
+
+const nunjucksEnv = configureNunjucks(app, APP_VIEWS);
+app.set("view engine", nunjucksEnv);
 
 i18next
   .use(Backend)
@@ -121,6 +123,8 @@ i18next
 
 app.use(i18nextMiddleware.handle(i18next));
 
+preloadTemplates(nunjucksEnv); // Must come after nunjucks and i18n
+
 app.use(cookieParser());
 
 // Generate a new session ID asynchronously if no session cookie

src/app/development/middleware.test.ts

@@ -17,7 +17,7 @@ const pagesAndContextsStub = {
   },
 };
 const middleware = proxyquire("./middleware", {
-  "../../test-utils/pages-and-contexts": pagesAndContextsStub,
+  "../../config/pages-and-contexts": pagesAndContextsStub,
   "fs/promises": fsReadDirStub,
 });
 

src/app/development/middleware.ts

@@ -10,7 +10,7 @@ import { generateQrCodeImageData } from "../shared/qrCodeHelper";
 import { getAppStoreRedirectUrl } from "../shared/appDownloadHelper";
 import PAGES from "../../constants/ipv-pages";
 import { getIpvPageTemplatePath, getTemplatePath } from "../../lib/paths";
-import { pagesAndContexts } from "../../test-utils/pages-and-contexts";
+import { pagesAndContexts } from "../../config/pages-and-contexts";
 
 interface RadioOption {
   text: string;

src/config/nunjucks.ts

@@ -4,6 +4,9 @@ import i18next from "i18next";
 import nunjucks, { Environment } from "nunjucks";
 import { kebabCaseToPascalCase } from "../app/shared/stringHelper";
 import config from "./config";
+import { logger } from "../lib/logger";
+import { getIpvPageTemplatePath } from "../lib/paths";
+import { pagesAndContexts } from "./pages-and-contexts";
 
 interface FilterContext {
   ctx: {
@@ -85,3 +88,21 @@ export const configureNunjucks = (
   nunjucksEnv.addGlobal("addLanguageParam", addLanguageParam);
   return nunjucksEnv;
 };
+
+// Usually nunjucks will load templates on-demand (and are then cached indefinitely).
+// However, this can trigger overload-protection as it's a synchronous blocking call.
+// By pre-rendering each template once, we can force all the templates to be loaded at startup.
+export const preloadTemplates = (nunjucksEnv: Environment): void => {
+  if (config.TEMPLATE_CACHING) {
+    logger.info("Preloading templates");
+    const dummyContext = {
+      i18n: {
+        language: "en",
+      },
+    };
+
+    Object.keys(pagesAndContexts).forEach((pageId) => {
+      nunjucksEnv.render(getIpvPageTemplatePath(pageId), dummyContext);
+    });
+  }
+};