Use permanent cache for translation files on production (#181377)

## Summary

Fix #83409

Use a permanent cache (`public, max-age=365d, immutable`) for
translation files when in production (`dist`), similar to what we're
doing for static assets.

Translation files cache busting is a little tricky, because it doesn't
only depend on the version (enabling or disabling a custom plugin can
change the translations while not changing the build hash), so we're
using a custom hash generated from the content of the current
translation file (which was already used to generate the `etag` header
previously).

---------

Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>

Author: pgayvallet

packages/core/i18n/core-i18n-server-internal/index.ts

@@ -6,5 +6,5 @@
  * Side Public License, v 1.
  */
 
-export type { I18nConfigType } from './src';
+export type { I18nConfigType, InternalI18nServicePreboot } from './src';
 export { config, I18nService } from './src';

packages/core/i18n/core-i18n-server-internal/src/i18n_service.test.ts

@@ -37,12 +37,13 @@ describe('I18nService', () => {
   let configService: ReturnType<typeof configServiceMock.create>;
   let httpPreboot: ReturnType<typeof httpServiceMock.createInternalPrebootContract>;
   let httpSetup: ReturnType<typeof httpServiceMock.createInternalSetupContract>;
+  let coreContext: ReturnType<typeof mockCoreContext.create>;
 
   beforeEach(() => {
     jest.clearAllMocks();
     configService = getConfigService();
 
-    const coreContext = mockCoreContext.create({ configService });
+    coreContext = mockCoreContext.create({ configService });
     service = new I18nService(coreContext);
 
     httpPreboot = httpServiceMock.createInternalPrebootContract();
@@ -73,13 +74,15 @@ describe('I18nService', () => {
       expect(initTranslationsMock).toHaveBeenCalledWith('en', translationFiles);
     });
 
-    it('calls `registerRoutesMock` with the correct parameters', async () => {
+    it('calls `registerRoutes` with the correct parameters', async () => {
       await service.preboot({ pluginPaths: [], http: httpPreboot });
 
       expect(registerRoutesMock).toHaveBeenCalledTimes(1);
       expect(registerRoutesMock).toHaveBeenCalledWith({
         locale: 'en',
         router: expect.any(Object),
+        isDist: coreContext.env.packageInfo.dist,
+        translationHash: expect.any(String),
       });
     });
   });
@@ -114,13 +117,15 @@ describe('I18nService', () => {
       expect(initTranslationsMock).toHaveBeenCalledWith('en', translationFiles);
     });
 
-    it('calls `registerRoutesMock` with the correct parameters', async () => {
+    it('calls `registerRoutes` with the correct parameters', async () => {
       await service.setup({ pluginPaths: [], http: httpSetup });
 
       expect(registerRoutesMock).toHaveBeenCalledTimes(1);
       expect(registerRoutesMock).toHaveBeenCalledWith({
         locale: 'en',
         router: expect.any(Object),
+        isDist: coreContext.env.packageInfo.dist,
+        translationHash: expect.any(String),
       });
     });
 

packages/core/i18n/core-i18n-server-internal/src/i18n_service.ts

@@ -7,6 +7,8 @@
  */
 
 import { firstValueFrom } from 'rxjs';
+import { createHash } from 'crypto';
+import { i18n, Translation } from '@kbn/i18n';
 import type { Logger } from '@kbn/logging';
 import type { IConfigService } from '@kbn/config';
 import type { CoreContext } from '@kbn/core-base-server-internal';
@@ -30,29 +32,42 @@ export interface SetupDeps {
   pluginPaths: string[];
 }
 
+export interface InternalI18nServicePreboot {
+  getTranslationHash(): string;
+}
+
 export class I18nService {
   private readonly log: Logger;
   private readonly configService: IConfigService;
 
-  constructor(coreContext: CoreContext) {
+  constructor(private readonly coreContext: CoreContext) {
     this.log = coreContext.logger.get('i18n');
     this.configService = coreContext.configService;
   }
 
-  public async preboot({ pluginPaths, http }: PrebootDeps) {
-    const { locale } = await this.initTranslations(pluginPaths);
-    http.registerRoutes('', (router) => registerRoutes({ router, locale }));
+  public async preboot({ pluginPaths, http }: PrebootDeps): Promise<InternalI18nServicePreboot> {
+    const { locale, translationHash } = await this.initTranslations(pluginPaths);
+    const { dist: isDist } = this.coreContext.env.packageInfo;
+    http.registerRoutes('', (router) =>
+      registerRoutes({ router, locale, isDist, translationHash })
+    );
+
+    return {
+      getTranslationHash: () => translationHash,
+    };
   }
 
   public async setup({ pluginPaths, http }: SetupDeps): Promise<I18nServiceSetup> {
-    const { locale, translationFiles } = await this.initTranslations(pluginPaths);
+    const { locale, translationFiles, translationHash } = await this.initTranslations(pluginPaths);
 
     const router = http.createRouter('');
-    registerRoutes({ router, locale });
+    const { dist: isDist } = this.coreContext.env.packageInfo;
+    registerRoutes({ router, locale, isDist, translationHash });
 
     return {
       getLocale: () => locale,
       getTranslationFiles: () => translationFiles,
+      getTranslationHash: () => translationHash,
     };
   }
 
@@ -69,6 +84,13 @@ export class I18nService {
     this.log.debug(`Using translation files: [${translationFiles.join(', ')}]`);
     await initTranslations(locale, translationFiles);
 
-    return { locale, translationFiles };
+    const translationHash = getTranslationHash(i18n.getTranslation());
+
+    return { locale, translationFiles, translationHash };
   }
 }
+
+const getTranslationHash = (translations: Translation) => {
+  const serialized = JSON.stringify(translations);
+  return createHash('sha256').update(serialized).digest('hex').slice(0, 12);
+};

packages/core/i18n/core-i18n-server-internal/src/index.ts

@@ -9,3 +9,4 @@
 export { config } from './i18n_config';
 export type { I18nConfigType } from './i18n_config';
 export { I18nService } from './i18n_service';
+export type { InternalI18nServicePreboot } from './i18n_service';

packages/core/i18n/core-i18n-server-internal/src/routes/index.ts

@@ -9,6 +9,16 @@
 import type { IRouter } from '@kbn/core-http-server';
 import { registerTranslationsRoute } from './translations';
 
-export const registerRoutes = ({ router, locale }: { router: IRouter; locale: string }) => {
-  registerTranslationsRoute(router, locale);
+export const registerRoutes = ({
+  router,
+  locale,
+  isDist,
+  translationHash,
+}: {
+  router: IRouter;
+  locale: string;
+  isDist: boolean;
+  translationHash: string;
+}) => {
+  registerTranslationsRoute({ router, locale, isDist, translationHash });
 };

packages/core/i18n/core-i18n-server-internal/src/routes/translations.test.ts

@@ -12,11 +12,27 @@ import { registerTranslationsRoute } from './translations';
 describe('registerTranslationsRoute', () => {
   test('registers route with expected options', () => {
     const router = mockRouter.create();
-    registerTranslationsRoute(router, 'en');
-    expect(router.get).toHaveBeenCalledTimes(1);
+    registerTranslationsRoute({
+      router,
+      locale: 'en',
+      isDist: true,
+      translationHash: 'XXXX',
+    });
+    expect(router.get).toHaveBeenCalledTimes(2);
     expect(router.get).toHaveBeenNthCalledWith(
       1,
-      expect.objectContaining({ options: { access: 'public', authRequired: false } }),
+      expect.objectContaining({
+        path: '/translations/{locale}.json',
+        options: { access: 'public', authRequired: false },
+      }),
+      expect.any(Function)
+    );
+    expect(router.get).toHaveBeenNthCalledWith(
+      2,
+      expect.objectContaining({
+        path: '/translations/XXXX/{locale}.json',
+        options: { access: 'public', authRequired: false },
+      }),
       expect.any(Function)
     );
   });

packages/core/i18n/core-i18n-server-internal/src/routes/translations.ts

@@ -6,54 +6,81 @@
  * Side Public License, v 1.
  */
 
-import { createHash } from 'crypto';
 import { i18n } from '@kbn/i18n';
 import { schema } from '@kbn/config-schema';
 import type { IRouter } from '@kbn/core-http-server';
 
+const MINUTE = 60;
+const HOUR = 60 * MINUTE;
+const DAY = 24 * HOUR;
+
 interface TranslationCache {
   translations: string;
   hash: string;
 }
 
-export const registerTranslationsRoute = (router: IRouter, locale: string) => {
+export const registerTranslationsRoute = ({
+  router,
+  locale,
+  translationHash,
+  isDist,
+}: {
+  router: IRouter;
+  locale: string;
+  translationHash: string;
+  isDist: boolean;
+}) => {
   let translationCache: TranslationCache;
 
-  router.get(
-    {
-      path: '/translations/{locale}.json',
-      validate: {
-        params: schema.object({
-          locale: schema.string(),
-        }),
-      },
-      options: {
-        access: 'public',
-        authRequired: false,
-      },
-    },
-    (ctx, req, res) => {
-      if (req.params.locale.toLowerCase() !== locale.toLowerCase()) {
-        return res.notFound({
-          body: `Unknown locale: ${req.params.locale}`,
-        });
-      }
-      if (!translationCache) {
-        const translations = JSON.stringify(i18n.getTranslation());
-        const hash = createHash('sha1').update(translations).digest('hex');
-        translationCache = {
-          translations,
-          hash,
-        };
-      }
-      return res.ok({
-        headers: {
-          'content-type': 'application/json',
-          'cache-control': 'must-revalidate',
-          etag: translationCache.hash,
+  ['/translations/{locale}.json', `/translations/${translationHash}/{locale}.json`].forEach(
+    (routePath) => {
+      router.get(
+        {
+          path: routePath,
+          validate: {
+            params: schema.object({
+              locale: schema.string(),
+            }),
+          },
+          options: {
+            access: 'public',
+            authRequired: false,
+          },
         },
-        body: translationCache.translations,
-      });
+        (ctx, req, res) => {
+          if (req.params.locale.toLowerCase() !== locale.toLowerCase()) {
+            return res.notFound({
+              body: `Unknown locale: ${req.params.locale}`,
+            });
+          }
+          if (!translationCache) {
+            const translations = JSON.stringify(i18n.getTranslation());
+            translationCache = {
+              translations,
+              hash: translationHash,
+            };
+          }
+
+          let headers: Record<string, string>;
+          if (isDist) {
+            headers = {
+              'content-type': 'application/json',
+              'cache-control': `public, max-age=${365 * DAY}, immutable`,
+            };
+          } else {
+            headers = {
+              'content-type': 'application/json',
+              'cache-control': 'must-revalidate',
+              etag: translationCache.hash,
+            };
+          }
+
+          return res.ok({
+            headers,
+            body: translationCache.translations,
+          });
+        }
+      );
     }
   );
 };

packages/core/i18n/core-i18n-server-mocks/src/i18n_service.mock.ts

@@ -7,17 +7,29 @@
  */
 
 import type { PublicMethodsOf } from '@kbn/utility-types';
-import type { I18nService } from '@kbn/core-i18n-server-internal';
+import type { I18nService, InternalI18nServicePreboot } from '@kbn/core-i18n-server-internal';
 import type { I18nServiceSetup } from '@kbn/core-i18n-server';
 
 const createSetupContractMock = () => {
   const mock: jest.Mocked<I18nServiceSetup> = {
     getLocale: jest.fn(),
     getTranslationFiles: jest.fn(),
+    getTranslationHash: jest.fn(),
   };
 
   mock.getLocale.mockReturnValue('en');
   mock.getTranslationFiles.mockReturnValue([]);
+  mock.getTranslationHash.mockReturnValue('MOCK_HASH');
+
+  return mock;
+};
+
+const createInternalPrebootMock = () => {
+  const mock: jest.Mocked<InternalI18nServicePreboot> = {
+    getTranslationHash: jest.fn(),
+  };
+
+  mock.getTranslationHash.mockReturnValue('MOCK_HASH');
 
   return mock;
 };
@@ -38,4 +50,5 @@ const createMock = () => {
 export const i18nServiceMock = {
   create: createMock,
   createSetupContract: createSetupContractMock,
+  createInternalPrebootContract: createInternalPrebootMock,
 };

packages/core/i18n/core-i18n-server/src/types.ts

@@ -19,4 +19,9 @@ export interface I18nServiceSetup {
    * Return the absolute paths to translation files currently in use.
    */
   getTranslationFiles(): string[];
+
+  /**
+   * Returns the hash generated from the current translations.
+   */
+  getTranslationHash(): string;
 }