Shared Revalidate Timings (#64370)

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This creates a new `SharedRevalidateTimings` type that is safe to share
amongst different points within the framework for sharing revalidation
timings. This is a precursor to #64313 which freezes loaded manifests.

Using the `SharedRevalidateTimings` type, we no-longer have to modify
the in-memory instance of the prerender manifest to share the
revalidation timings for different routes.

Closes NEXT-3083

Author: wyattjoh

packages/next/src/server/base-server.ts

@@ -124,6 +124,7 @@ import {
 import { matchNextDataPathname } from './lib/match-next-data-pathname'
 import getRouteFromAssetPath from '../shared/lib/router/utils/get-route-from-asset-path'
 import { stripInternalHeaders } from './internal-utils'
+import { toRoute } from './lib/to-route'
 
 export type FindComponentsResult = {
   components: LoadComponentsReturnType
@@ -1676,8 +1677,7 @@ export default abstract class Server<ServerOptions extends Options = Options> {
     ) {
       isSSG = true
     } else if (!this.renderOpts.dev) {
-      isSSG ||=
-        !!prerenderManifest.routes[pathname === '/index' ? '/' : pathname]
+      isSSG ||= !!prerenderManifest.routes[toRoute(pathname)]
     }
 
     // Toggle whether or not this is a Data request

packages/next/src/server/lib/incremental-cache/index.ts

@@ -1,12 +1,12 @@
 import type { CacheFs } from '../../../shared/lib/utils'
 import type { PrerenderManifest } from '../../../build'
+import type { Revalidate } from '../revalidate'
 import type {
   IncrementalCacheValue,
   IncrementalCacheEntry,
 } from '../../response-cache'
 import FetchCache from './fetch-cache'
 import FileSystemCache from './file-system-cache'
-import path from '../../../shared/lib/isomorphic/path'
 import { encodeText } from '../../stream-utils/encode-decode'
 import { encode } from '../../../shared/lib/base64-arraybuffer'
 import { normalizePagePath } from '../../../shared/lib/page-path/normalize-page-path'
@@ -17,10 +17,8 @@ import {
   NEXT_CACHE_REVALIDATE_TAG_TOKEN_HEADER,
   PRERENDER_REVALIDATE_HEADER,
 } from '../../../lib/constants'
-
-function toRoute(pathname: string): string {
-  return pathname.replace(/\/$/, '').replace(/\/index$/, '') || '/'
-}
+import { toRoute } from '../to-route'
+import { SharedRevalidateTimings } from './shared-revalidate-timings'
 
 export interface CacheHandlerContext {
   fs?: CacheFs
@@ -72,6 +70,11 @@ export class IncrementalCache {
   isOnDemandRevalidate?: boolean
   private locks = new Map<string, Promise<void>>()
   private unlocks = new Map<string, () => Promise<void>>()
+  /**
+   * The revalidate timings for routes. This will source the timings from the
+   * prerender manifest until the in-memory cache is updated with new timings.
+   */
+  private readonly revalidateTimings: SharedRevalidateTimings
 
   constructor({
     fs,
@@ -139,6 +142,7 @@ export class IncrementalCache {
     this.requestProtocol = requestProtocol
     this.allowedRevalidateHeaderKeys = allowedRevalidateHeaderKeys
     this.prerenderManifest = getPrerenderManifest()
+    this.revalidateTimings = new SharedRevalidateTimings(this.prerenderManifest)
     this.fetchCacheKeyPrefix = fetchCacheKeyPrefix
     let revalidatedTags: string[] = []
 
@@ -178,18 +182,16 @@ export class IncrementalCache {
     pathname: string,
     fromTime: number,
     dev?: boolean
-  ): number | false {
+  ): Revalidate {
     // in development we don't have a prerender-manifest
     // and default to always revalidating to allow easier debugging
     if (dev) return new Date().getTime() - 1000
 
     // if an entry isn't present in routes we fallback to a default
-    // of revalidating after 1 second
-    const { initialRevalidateSeconds } = this.prerenderManifest.routes[
-      toRoute(pathname)
-    ] || {
-      initialRevalidateSeconds: 1,
-    }
+    // of revalidating after 1 second.
+    const initialRevalidateSeconds =
+      this.revalidateTimings.get(toRoute(pathname)) ?? 1
+
     const revalidateAfter =
       typeof initialRevalidateSeconds === 'number'
         ? initialRevalidateSeconds * 1000 + fromTime
@@ -464,11 +466,10 @@ export class IncrementalCache {
       }
     }
 
-    const curRevalidate =
-      this.prerenderManifest.routes[toRoute(cacheKey)]?.initialRevalidateSeconds
+    const curRevalidate = this.revalidateTimings.get(toRoute(cacheKey))
 
     let isStale: boolean | -1 | undefined
-    let revalidateAfter: false | number
+    let revalidateAfter: Revalidate
 
     if (cacheData?.lastModified === -1) {
       isStale = -1
@@ -554,19 +555,12 @@ export class IncrementalCache {
     pathname = this._getPathname(pathname, ctx.fetchCache)
 
     try {
-      // we use the prerender manifest memory instance
-      // to store revalidate timings for calculating
-      // revalidateAfter values so we update this on set
+      // Set the value for the revalidate seconds so if it changes we can
+      // update the cache with the new value.
       if (typeof ctx.revalidate !== 'undefined' && !ctx.fetchCache) {
-        this.prerenderManifest.routes[pathname] = {
-          dataRoute: path.posix.join(
-            '/_next/data',
-            `${normalizePagePath(pathname)}.json`
-          ),
-          srcRoute: null, // FIXME: provide actual source route, however, when dynamically appending it doesn't really matter
-          initialRevalidateSeconds: ctx.revalidate,
-        }
+        this.revalidateTimings.set(pathname, ctx.revalidate)
       }
+
       await this.cacheHandler?.set(pathname, data, ctx)
     } catch (error) {
       console.warn('Failed to update prerender cache for', pathname, error)

packages/next/src/server/lib/incremental-cache/shared-revalidate-timings.test.ts

@@ -0,0 +1,57 @@
+import { SharedRevalidateTimings } from './shared-revalidate-timings'
+
+describe('SharedRevalidateTimings', () => {
+  let sharedRevalidateTimings: SharedRevalidateTimings
+  let prerenderManifest
+
+  beforeEach(() => {
+    prerenderManifest = {
+      routes: {
+        '/route1': {
+          initialRevalidateSeconds: 10,
+          dataRoute: null,
+          srcRoute: null,
+        },
+        '/route2': {
+          initialRevalidateSeconds: 20,
+          dataRoute: null,
+          srcRoute: null,
+        },
+      },
+    }
+    sharedRevalidateTimings = new SharedRevalidateTimings(prerenderManifest)
+  })
+
+  afterEach(() => {
+    sharedRevalidateTimings.clear()
+  })
+
+  it('should get revalidate timing from in-memory cache', () => {
+    sharedRevalidateTimings.set('/route1', 15)
+    const revalidate = sharedRevalidateTimings.get('/route1')
+    expect(revalidate).toBe(15)
+  })
+
+  it('should get revalidate timing from prerender manifest if not in cache', () => {
+    const revalidate = sharedRevalidateTimings.get('/route2')
+    expect(revalidate).toBe(20)
+  })
+
+  it('should return undefined if revalidate timing not found', () => {
+    const revalidate = sharedRevalidateTimings.get('/route3')
+    expect(revalidate).toBeUndefined()
+  })
+
+  it('should set revalidate timing in cache', () => {
+    sharedRevalidateTimings.set('/route3', 30)
+    const revalidate = sharedRevalidateTimings.get('/route3')
+    expect(revalidate).toBe(30)
+  })
+
+  it('should clear the in-memory cache', () => {
+    sharedRevalidateTimings.set('/route3', 30)
+    sharedRevalidateTimings.clear()
+    const revalidate = sharedRevalidateTimings.get('/route3')
+    expect(revalidate).toBeUndefined()
+  })
+})

packages/next/src/server/lib/incremental-cache/shared-revalidate-timings.ts

@@ -0,0 +1,63 @@
+import type { PrerenderManifest } from '../../../build'
+import type { Revalidate } from '../revalidate'
+
+/**
+ * A shared cache of revalidate timings for routes. This cache is used so we
+ * don't have to modify the prerender manifest when we want to update the
+ * revalidate timings for a route.
+ */
+export class SharedRevalidateTimings {
+  /**
+   * The in-memory cache of revalidate timings for routes. This cache is
+   * populated when the cache is updated with new timings.
+   */
+  private static readonly timings = new Map<string, Revalidate>()
+
+  constructor(
+    /**
+     * The prerender manifest that contains the initial revalidate timings for
+     * routes.
+     */
+    private readonly prerenderManifest: Pick<PrerenderManifest, 'routes'>
+  ) {}
+
+  /**
+   * Try to get the revalidate timings for a route. This will first try to get
+   * the timings from the in-memory cache. If the timings are not present in the
+   * in-memory cache, then the timings will be sourced from the prerender
+   * manifest.
+   *
+   * @param route the route to get the revalidate timings for
+   * @returns the revalidate timings for the route, or undefined if the timings
+   *          are not present in the in-memory cache or the prerender manifest
+   */
+  public get(route: string): Revalidate | undefined {
+    // This is a copy on write cache that is updated when the cache is updated.
+    // If the cache is never written to, then the timings will be sourced from
+    // the prerender manifest.
+    let revalidate = SharedRevalidateTimings.timings.get(route)
+    if (typeof revalidate !== 'undefined') return revalidate
+
+    revalidate = this.prerenderManifest.routes[route]?.initialRevalidateSeconds
+    if (typeof revalidate !== 'undefined') return revalidate
+
+    return undefined
+  }
+
+  /**
+   * Set the revalidate timings for a route.
+   *
+   * @param route the route to set the revalidate timings for
+   * @param revalidate the revalidate timings for the route
+   */
+  public set(route: string, revalidate: Revalidate) {
+    SharedRevalidateTimings.timings.set(route, revalidate)
+  }
+
+  /**
+   * Clear the in-memory cache of revalidate timings for routes.
+   */
+  public clear() {
+    SharedRevalidateTimings.timings.clear()
+  }
+}

packages/next/src/server/lib/to-route.test.ts

@@ -0,0 +1,33 @@
+import { toRoute } from './to-route'
+
+describe('toRoute Function', () => {
+  it('should remove trailing slash', () => {
+    const result = toRoute('/example/')
+    expect(result).toBe('/example')
+  })
+
+  it('should remove trailing `/index`', () => {
+    const result = toRoute('/example/index')
+    expect(result).toBe('/example')
+  })
+
+  it('should return `/` when input is `/index`', () => {
+    const result = toRoute('/index')
+    expect(result).toBe('/')
+  })
+
+  it('should return `/` when input is `/index/`', () => {
+    const result = toRoute('/index/')
+    expect(result).toBe('/')
+  })
+
+  it('should return `/` when input is only a slash', () => {
+    const result = toRoute('/')
+    expect(result).toBe('/')
+  })
+
+  it('should return `/` when input is empty', () => {
+    const result = toRoute('')
+    expect(result).toBe('/')
+  })
+})

packages/next/src/server/lib/to-route.ts

@@ -0,0 +1,26 @@
+/**
+ * This transforms a URL pathname into a route. It removes any trailing slashes
+ * and the `/index` suffix.
+ *
+ * @param {string} pathname - The URL path that needs to be optimized.
+ * @returns {string} - The route
+ *
+ * @example
+ * // returns '/example'
+ * toRoute('/example/index/');
+ *
+ * @example
+ * // returns '/example'
+ * toRoute('/example/');
+ *
+ * @example
+ * // returns '/'
+ * toRoute('/index/');
+ *
+ * @example
+ * // returns '/'
+ * toRoute('/');
+ */
+export function toRoute(pathname: string): string {
+  return pathname.replace(/(?:\/index)?\/?$/, '') || '/'
+}

packages/next/src/server/response-cache/types.ts

@@ -72,9 +72,9 @@ interface IncrementalCachedPageValue {
 }
 
 export type IncrementalCacheEntry = {
-  curRevalidate?: number | false
+  curRevalidate?: Revalidate
   // milliseconds to revalidate after
-  revalidateAfter: number | false
+  revalidateAfter: Revalidate
   // -1 here dictates a blocking revalidate should be used
   isStale?: boolean | -1
   value: IncrementalCacheValue | null