Add next.config.js option to override default keepAlive (vercel#2…

…7709)

Follow up to vercel#27376 so users can disable keep-alive.

See comment vercel#27376 (comment)

docs/api-reference/next.config.js/disabling-http-keep-alive.md

@@ -0,0 +1,36 @@
+---
+description: Next.js will automatically use HTTP Keep-Alive by default. Learn more about how to disable HTTP Keep-Alive here.
+---
+
+# Disabling HTTP Keep-Alive
+
+Next.js automatically polyfills [node-fetch](/docs/basic-features/supported-browsers-features#polyfills) and enables [HTTP Keep-Alive](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Keep-Alive) by default. You may want to disable HTTP Keep-Alive for certain `fetch()` calls or globally.
+
+For a single `fetch()` call, you can add the agent option:
+
+```js
+import { Agent } from 'https'
+
+const url = 'https://example.com'
+const agent = new Agent({ keepAlive: false })
+fetch(url, { agent })
+```
+
+To override all `fetch()` calls globally, you can use `next.config.js`:
+
+```js
+module.exports = {
+  httpAgentOptions: {
+    keepAlive: false,
+  },
+}
+```
+
+## Related
+
+<div class="card">
+  <a href="/docs/api-reference/next.config.js/introduction.md">
+    <b>Introduction to next.config.js:</b>
+    <small>Learn more about the configuration file used by Next.js.</small>
+  </a>
+</div>

docs/manifest.json

@@ -348,6 +348,10 @@
               "title": "Disabling ETag Generation",
               "path": "/docs/api-reference/next.config.js/disabling-etag-generation.md"
             },
+            {
+              "title": "Disabling HTTP Keep-Alive",
+              "path": "/docs/api-reference/next.config.js/disabling-http-keep-alive.md"
+            },
             {
               "title": "Setting a custom build directory",
               "path": "/docs/api-reference/next.config.js/setting-a-custom-build-directory.md"

packages/next/build/index.ts

@@ -743,6 +743,7 @@ export default async function build(
             distDir,
             isLikeServerless,
             runtimeEnvConfig,
+            config.httpAgentOptions,
             config.i18n?.locales,
             config.i18n?.defaultLocale
           )
@@ -812,6 +813,7 @@ export default async function build(
                     distDir,
                     isLikeServerless,
                     runtimeEnvConfig,
+                    config.httpAgentOptions,
                     config.i18n?.locales,
                     config.i18n?.defaultLocale,
                     isPageStaticSpan.id

packages/next/build/utils.ts

@@ -32,6 +32,8 @@ import { normalizeLocalePath } from '../shared/lib/i18n/normalize-locale-path'
 import * as Log from './output/log'
 import { loadComponents } from '../server/load-components'
 import { trace } from '../telemetry/trace'
+import { setHttpAgentOptions } from '../server/config'
+import { NextConfigComplete } from '../server/config-shared'
 
 const fileGzipStats: { [k: string]: Promise<number> | undefined } = {}
 const fsStatGzip = (file: string) => {
@@ -815,6 +817,7 @@ export async function isPageStatic(
   distDir: string,
   serverless: boolean,
   runtimeEnvConfig: any,
+  httpAgentOptions: NextConfigComplete['httpAgentOptions'],
   locales?: string[],
   defaultLocale?: string,
   parentId?: any
@@ -833,6 +836,7 @@ export async function isPageStatic(
   return isPageStaticSpan.traceAsyncFn(async () => {
     try {
       require('../shared/lib/runtime-config').setConfig(runtimeEnvConfig)
+      setHttpAgentOptions(httpAgentOptions)
       const components = await loadComponents(distDir, page, serverless)
       const mod = components.ComponentMod
       const Comp = mod.default || mod

packages/next/export/index.ts

@@ -570,6 +570,7 @@ export default async function exportApp(
             disableOptimizedLoading:
               nextConfig.experimental.disableOptimizedLoading,
             parentSpanId: pageExportSpan.id,
+            httpAgentOptions: nextConfig.httpAgentOptions,
           })
 
           for (const validation of result.ampValidations || []) {

packages/next/export/worker.ts

@@ -19,6 +19,8 @@ import { normalizeLocalePath } from '../shared/lib/i18n/normalize-locale-path'
 import { trace } from '../telemetry/trace'
 import { isInAmpMode } from '../shared/lib/amp'
 import { resultFromChunks, resultToChunks } from '../server/utils'
+import { NextConfigComplete } from '../server/config-shared'
+import { setHttpAgentOptions } from '../server/config'
 
 const envConfig = require('../shared/lib/runtime-config')
 
@@ -55,6 +57,7 @@ interface ExportPageInput {
   optimizeCss: any
   disableOptimizedLoading: any
   parentSpanId: any
+  httpAgentOptions: NextConfigComplete['httpAgentOptions']
 }
 
 interface ExportPageResults {
@@ -103,7 +106,9 @@ export default async function exportPage({
   optimizeImages,
   optimizeCss,
   disableOptimizedLoading,
+  httpAgentOptions,
 }: ExportPageInput): Promise<ExportPageResults> {
+  setHttpAgentOptions(httpAgentOptions)
   const exportPageSpan = trace('export-page-worker', parentSpanId)
 
   return exportPageSpan.traceAsyncFn(async () => {

packages/next/server/config-shared.ts

@@ -76,7 +76,7 @@ export type NextConfig = { [key: string]: any } & {
   reactStrictMode?: boolean
   publicRuntimeConfig?: { [key: string]: any }
   serverRuntimeConfig?: { [key: string]: any }
-
+  httpAgentOptions?: { keepAlive?: boolean }
   future?: {
     /**
      * @deprecated this options was moved to the top level
@@ -153,6 +153,9 @@ export const defaultConfig: NextConfig = {
   serverRuntimeConfig: {},
   publicRuntimeConfig: {},
   reactStrictMode: false,
+  httpAgentOptions: {
+    keepAlive: true,
+  },
   experimental: {
     cpus: Math.max(
       1,

packages/next/server/config.ts

@@ -1,6 +1,8 @@
 import chalk from 'chalk'
 import findUp from 'next/dist/compiled/find-up'
 import { basename, extname } from 'path'
+import { Agent as HttpAgent } from 'http'
+import { Agent as HttpsAgent } from 'https'
 import * as Log from '../build/output/log'
 import { CONFIG_FILE, PHASE_DEVELOPMENT_SERVER } from '../shared/lib/constants'
 import { execOnce } from '../shared/lib/utils'
@@ -304,6 +306,12 @@ function assignDefaults(userConfig: { [key: string]: any }) {
     }
   }
 
+  // TODO: Change defaultConfig type to NextConfigComplete
+  // so we don't need "!" here.
+  setHttpAgentOptions(
+    result.httpAgentOptions || defaultConfig.httpAgentOptions!
+  )
+
   if (result.i18n) {
     const { i18n } = result
     const i18nType = typeof i18n
@@ -517,11 +525,30 @@ export default async function loadConfig(
     }
   }
 
-  return defaultConfig as NextConfigComplete
+  const completeConfig = defaultConfig as NextConfigComplete
+  setHttpAgentOptions(completeConfig.httpAgentOptions)
+  return completeConfig
 }
 
 export function isTargetLikeServerless(target: string) {
   const isServerless = target === 'serverless'
   const isServerlessTrace = target === 'experimental-serverless-trace'
   return isServerless || isServerlessTrace
 }
+
+export function setHttpAgentOptions(
+  options: NextConfigComplete['httpAgentOptions']
+) {
+  if ((global as any).__NEXT_HTTP_AGENT) {
+    // We only need to assign once because we want
+    // to resuse the same agent for all requests.
+    return
+  }
+
+  if (!options) {
+    throw new Error('Expected config.httpAgentOptions to be an object')
+  }
+
+  ;(global as any).__NEXT_HTTP_AGENT = new HttpAgent(options)
+  ;(global as any).__NEXT_HTTPS_AGENT = new HttpsAgent(options)
+}

packages/next/server/dev/next-dev-server.ts

@@ -566,7 +566,11 @@ export default class DevServer extends Server {
     // from waiting on them for the page to load in dev mode
 
     const __getStaticPaths = async () => {
-      const { publicRuntimeConfig, serverRuntimeConfig } = this.nextConfig
+      const {
+        publicRuntimeConfig,
+        serverRuntimeConfig,
+        httpAgentOptions,
+      } = this.nextConfig
       const { locales, defaultLocale } = this.nextConfig.i18n || {}
 
       const paths = await this.staticPathsWorker.loadStaticPaths(
@@ -577,6 +581,7 @@ export default class DevServer extends Server {
           publicRuntimeConfig,
           serverRuntimeConfig,
         },
+        httpAgentOptions,
         locales,
         defaultLocale
       )

packages/next/server/dev/static-paths-worker.ts

@@ -1,4 +1,6 @@
 import { buildStaticPaths } from '../../build/utils'
+import { setHttpAgentOptions } from '../config'
+import { NextConfigComplete } from '../config-shared'
 import { loadComponents } from '../load-components'
 import '../node-polyfill-fetch'
 
@@ -14,6 +16,7 @@ export async function loadStaticPaths(
   pathname: string,
   serverless: boolean,
   config: RuntimeConfig,
+  httpAgentOptions: NextConfigComplete['httpAgentOptions'],
   locales?: string[],
   defaultLocale?: string
 ) {
@@ -25,6 +28,7 @@ export async function loadStaticPaths(
 
   // update work memory runtime-config
   require('../../shared/lib/runtime-config').setConfig(config)
+  setHttpAgentOptions(httpAgentOptions)
 
   const components = await loadComponents(distDir, pathname, serverless)
 

packages/next/server/node-polyfill-fetch.js

@@ -1,13 +1,9 @@
 import fetch, { Headers, Request, Response } from 'node-fetch'
-import { Agent as HttpAgent } from 'http'
-import { Agent as HttpsAgent } from 'https'
 
 // Polyfill fetch() in the Node.js environment
 if (!global.fetch) {
-  const httpAgent = new HttpAgent({ keepAlive: true })
-  const httpsAgent = new HttpsAgent({ keepAlive: true })
   const agent = ({ protocol }) =>
-    protocol === 'http:' ? httpAgent : httpsAgent
+    protocol === 'http:' ? global.__NEXT_HTTP_AGENT : global.__NEXT_HTTPS_AGENT
   const fetchWithAgent = (url, opts, ...rest) => {
     if (!opts) {
       opts = { agent }

test/integration/node-fetch-keep-alive/pages/blog/[slug].js

@@ -0,0 +1,23 @@
+export default function Blog(props) {
+  return <pre id="props">{JSON.stringify(props)}</pre>
+}
+
+export async function getStaticProps({ params: { slug } }) {
+  return { props: { slug } }
+}
+
+export async function getStaticPaths() {
+  const res = await fetch('http://localhost:44001')
+  const obj = await res.json()
+  if (obj.connection === 'keep-alive') {
+    return {
+      paths: [{ params: { slug: 'first' } }],
+      fallback: false,
+    }
+  }
+
+  return {
+    paths: [],
+    fallback: false,
+  }
+}