feat: add pre-request header calculation

ilc/config/custom-environment-variables.json5

@@ -29,6 +29,9 @@
     client: {
         protocol: 'ILC_CLIENT_PROTOCOL',
     },
+    tailor: {
+        maxFragmentRequestSize: 'ILC_MAX_FRAGMENT_REQUEST_SIZE',
+    },
     experiments: {
         enabled: 'ILC_EXPERIMENTS_ENABLED',
     },

ilc/config/default.json5

@@ -3,10 +3,10 @@
     port: 8233,
     cdnUrl: null,
     staticError: {
-        disasterFileContentPath: null
+        disasterFileContentPath: null,
     },
     registry: {
-        address: 'http://127.0.0.1:4001'
+        address: 'http://127.0.0.1:4001',
     },
     newrelic: {
         licenseKey: null,
@@ -16,13 +16,13 @@
          */
         customClientJsWrapper: null,
         automaticallyInjectBrowserMonitoring: true,
-        appName: null
+        appName: null,
     },
     overrideConfigTrustedOrigins: null,
     logger: {
         accessLog: {
-            ignoreUrls: ''
-        }
+            ignoreUrls: '',
+        },
     },
     static: {
         internalUrl: '/_ilc/',
@@ -33,6 +33,14 @@
     client: {
         protocol: 'https',
     },
+    tailor: {
+        // Disabled by default: enabling it changes what renders, so a deployment opts in
+        // rather than inheriting the decision. Set it to the byte ceiling your fragment
+        // servers actually accept — below their --max-http-header-size, whose own default is
+        // 16384. For stock node fragments 15872 is a reasonable starting point. 0 keeps the
+        // guard off, and an unusable value leaves it off with a WARN at startup.
+        maxFragmentRequestSize: 0,
+    },
     experiments: {
         // Global kill-switch. Set to false (e.g. via env in an incident) to send every
         // visitor to control with no assignment. Toggling this is a config change, not a deploy.

ilc/server/TransitionHooksExecutor.ts

@@ -37,7 +37,7 @@ export class TransitionHooksExecutor {
                         meta: route.meta,
                         url: route.reqUrl,
                         hostname: req.host,
-                        route: route.route,
+                        route: route.route as string,
                     },
                     log: req.log,
                     req: req.raw,

ilc/server/app.js

@@ -8,7 +8,7 @@ import { pingPluginFactroy } from './routes/pingPluginFactory';
 import { renderTemplateHandlerFactory } from './routes/renderTemplateHandlerFactory';
 import { wildcardRequestHandlerFactory } from './routes/wildcardRequestHandlerFactory';
 import { registerStatic } from './serveStatic';
-import tailorFactory from './tailor/factory';
+import { tailorFactory } from './tailor/factory';
 import { TransitionHooksExecutor } from './TransitionHooksExecutor';
 const { Test500Error } = require('./errorHandler/ErrorHandler');
 
@@ -118,6 +118,7 @@ module.exports = async function createApplication(registryService, pluginManager
         config.get('newrelic.customClientJsWrapper'),
         autoInjectNrMonitoring,
         logger,
+        config.get('tailor.maxFragmentRequestSize'),
     );
 
     app.all('*', wildcardRequestHandlerFactory(logger, registryService, errorHandler, transitionHooksExecutor, tailor));

ilc/server/routes/wildcardRequestHandlerFactory.ts

@@ -5,11 +5,11 @@ import { SlotCollection } from '../../common/Slot/SlotCollection';
 import UrlProcessor from '../../common/UrlProcessor';
 import i18n from '../i18n';
 import CspBuilderService from '../services/CspBuilderService';
-import tailorFactory from '../tailor/factory';
+import { tailorFactory } from '../tailor/factory';
 import { mergeConfigs, type OverrideConfig } from '../tailor/merge-configs';
 import { buildForwardedHeaders } from '../utils/helpers';
 import parseOverrideConfig from '../tailor/parse-override-config';
-import ServerRouter from '../tailor/server-router';
+import { ServerRouter } from '../tailor/server-router';
 import { TransitionHooksExecutor } from '../TransitionHooksExecutor';
 import { ErrorHandler } from '../types/ErrorHandler';
 import { IlcRouteHandlerMethod } from '../types/IlcRouteHandlerMethod';

ilc/server/tailor/factory.ts

@@ -0,0 +1,63 @@
+import newrelic from 'newrelic';
+
+import { Tailor, type TailorOptions } from './tailorx';
+import { fetchTemplate } from './fetch-template';
+import { filterHeaders } from './filter-headers';
+import errorHandlerSetup from './error-handler';
+import fragmentHooks from './fragment-hooks';
+import { ConfigsInjector } from './configs-injector';
+import processFragmentResponse from './process-fragment-response';
+import { requestFragmentFactory } from './request-fragment';
+import type { ServerRouter } from './server-router';
+import type { Registry } from '../types/Registry';
+
+type Logger = Pick<Console, 'debug' | 'warn'>;
+
+/**
+ * The error-handling service is injected by app.js and typed where it is defined; this module
+ * only passes it through, so it takes it as opaque.
+ */
+export function tailorFactory(
+    registryService: Registry,
+    errorHandlingService: unknown,
+    cdnUrl: string | null,
+    nrCustomClientJsWrapper: string | null = null,
+    nrAutomaticallyInjectClientScript = true,
+    logger: Logger,
+    maxFragmentRequestSize?: unknown,
+) {
+    const configsInjector = new ConfigsInjector(
+        newrelic,
+        cdnUrl,
+        nrCustomClientJsWrapper,
+        nrAutomaticallyInjectClientScript,
+    );
+
+    const tailorOptions: TailorOptions = {
+        fetchContext: async function (request: { router: ServerRouter }) {
+            return request.router.getFragmentsContext();
+        },
+        fetchTemplate: fetchTemplate(configsInjector, newrelic, registryService),
+        requestFragment: requestFragmentFactory(filterHeaders, processFragmentResponse, logger, {
+            maxRequestSize: maxFragmentRequestSize,
+        }),
+        processFragmentResponse,
+        filterHeaders,
+        fragmentHooks: {
+            insertStart: fragmentHooks.insertStart.bind(null, logger),
+            insertEnd: fragmentHooks.insertEnd,
+        },
+        botsGuardEnabled: true,
+        getAssetsToPreload: configsInjector.getAssetsToPreload,
+        filterResponseHeaders: (attributes: unknown, headers: Record<string, unknown>) =>
+            'set-cookie' in headers ? { 'set-cookie': headers['set-cookie'] } : {},
+        baseTemplatesCacheSize: 1,
+        shouldSetPrimaryFragmentAssetsToPreload: false,
+    };
+
+    const tailor = new Tailor(tailorOptions);
+
+    errorHandlerSetup(tailor, errorHandlingService);
+
+    return tailor;
+}