Add experimental proxy timeout option (#40289)

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## Bug

- [X] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

Fixes #36251

packages/next/server/config-schema.ts

@@ -320,6 +320,10 @@ const configSchema = {
         profiling: {
           type: 'boolean',
         },
+        proxyTimeout: {
+          minimum: 0,
+          type: 'number',
+        },
         runtime: {
           // automatic typing doesn't like enum
           enum: ['experimental-edge', 'nodejs'] as any,

packages/next/server/config-shared.ts

@@ -90,6 +90,7 @@ export interface ExperimentalConfig {
   cpus?: number
   sharedPool?: boolean
   profiling?: boolean
+  proxyTimeout?: number
   isrFlushToDisk?: boolean
   workerThreads?: boolean
   pageEnv?: boolean
@@ -550,6 +551,7 @@ export const defaultConfig: NextConfig = {
     isrFlushToDisk: true,
     workerThreads: false,
     pageEnv: false,
+    proxyTimeout: undefined,
     optimizeCss: false,
     nextScriptWorkers: false,
     scrollRestoration: false,

packages/next/server/next-server.ts

@@ -697,7 +697,10 @@ export default class NextNodeServer extends BaseServer {
       ws: true,
       // we limit proxy requests to 30s by default, in development
       // we don't time out WebSocket requests to allow proxying
-      proxyTimeout: upgradeHead && this.renderOpts.dev ? undefined : 30_000,
+      proxyTimeout:
+        upgradeHead && this.renderOpts.dev
+          ? undefined
+          : this.nextConfig.experimental.proxyTimeout || 30_000,
     })
 
     await new Promise((proxyResolve, proxyReject) => {