fix: track revalidate / cdn purge to ensure it finishes execution and is not suspended mid-execution

Author: pieh

src/run/handlers/cache.cts

@@ -244,19 +244,33 @@ export class NetlifyCacheHandler implements CacheHandler {
         if (requestContext?.didPagesRouterOnDemandRevalidate) {
           const tag = `_N_T_${key === '/index' ? '/' : key}`
           getLogger().debug(`Purging CDN cache for: [${tag}]`)
-          purgeCache({ tags: [tag] }).catch((error) => {
-            // TODO: add reporting here
-            getLogger()
-              .withError(error)
-              .error(`[NetlifyCacheHandler]: Purging the cache for tag ${tag} failed`)
-          })
+          requestContext.trackBackgroundWork(
+            purgeCache({ tags: [tag] }).catch((error) => {
+              // TODO: add reporting here
+              getLogger()
+                .withError(error)
+                .error(`[NetlifyCacheHandler]: Purging the cache for tag ${tag} failed`)
+            }),
+          )
         }
       }
     })
   }
 
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   async revalidateTag(tagOrTags: string | string[], ...args: any) {
+    const revalidateTagPromise = this.doRevalidateTag(tagOrTags, ...args)
+
+    const requestContext = getRequestContext()
+    if (requestContext) {
+      requestContext.trackBackgroundWork(revalidateTagPromise)
+    }
+
+    return revalidateTagPromise
+  }
+
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  private async doRevalidateTag(tagOrTags: string | string[], ...args: any) {
     getLogger().withFields({ tagOrTags, args }).debug('NetlifyCacheHandler.revalidateTag')
 
     const tags = Array.isArray(tagOrTags) ? tagOrTags : [tagOrTags]
@@ -275,7 +289,7 @@ export class NetlifyCacheHandler implements CacheHandler {
       }),
     )
 
-    purgeCache({ tags }).catch((error) => {
+    await purgeCache({ tags }).catch((error) => {
       // TODO: add reporting here
       getLogger()
         .withError(error)

src/run/revalidate.ts

@@ -1,4 +1,5 @@
 import type { ServerResponse } from 'node:http'
+import { isPromise } from 'node:util/types'
 
 import type { RequestContext } from './handlers/request-context.cjs'
 
@@ -12,7 +13,13 @@ export const nextResponseProxy = (res: ServerResponse, requestContext: RequestCo
         // eslint-disable-next-line @typescript-eslint/no-explicit-any
         return async function newRevalidate(...args: any[]) {
           requestContext.didPagesRouterOnDemandRevalidate = true
-          return originalValue?.apply(target, args)
+
+          const result = originalValue?.apply(target, args)
+          if (result && isPromise(result)) {
+            requestContext.trackBackgroundWork(result)
+          }
+
+          return result
         }
       }
       return originalValue

tests/fixtures/page-router/pages/api/revalidate.js

@@ -1,6 +1,9 @@
 export default async function handler(req, res) {
   try {
-    await res.revalidate('/static/revalidate-manual')
+    // res.revalidate returns a promise that can be awaited to wait for the revalidation to complete
+    // if user doesn't await it, we still want to ensure the revalidation is completed, so we internally track
+    // this as "background work" to ensure it completes before function suspends execution
+    res.revalidate('/static/revalidate-manual')
     return res.json({ code: 200, message: 'success' })
   } catch (err) {
     return res.status(500).send({ code: 500, message: err.message })