From cc4468c452f20d4101b813d6049984d5af5616fc Mon Sep 17 00:00:00 2001
From: Jimmy Lai <laijimmy0@gmail.com>
Date: Mon, 12 Dec 2022 12:09:06 +0100
Subject: [PATCH] add restart when next dev exceeds the memory limits

---
 packages/next/cli/next-dev.ts            | 73 ++++++++++++++----------
 packages/next/server/lib/start-server.ts | 15 ++++-
 2 files changed, 57 insertions(+), 31 deletions(-)

diff --git a/packages/next/cli/next-dev.ts b/packages/next/cli/next-dev.ts
index b0a689c84f660fa..713026254ee2cd0 100755
--- a/packages/next/cli/next-dev.ts
+++ b/packages/next/cli/next-dev.ts
@@ -13,6 +13,7 @@ import path from 'path'
 import type { NextConfig } from '../types'
 import type { NextConfigComplete } from '../server/config-shared'
 import { traceGlobals } from '../trace/shared'
+import cluster from 'cluster'
 
 let isTurboSession = false
 let sessionStopHandled = false
@@ -416,39 +417,53 @@ If you cannot make the changes above, but still want to try out\nNext.js v13 wit
     await telemetry.flush()
     return server
   } else {
-    startServer(devServerOptions)
-      .then(async (app) => {
-        const appUrl = `http://${app.hostname}:${app.port}`
-        startedDevelopmentServer(appUrl, `${host || '0.0.0.0'}:${app.port}`)
-        // Start preflight after server is listening and ignore errors:
-        preflight().catch(() => {})
-        // Finalize server bootup:
-        await app.prepare()
+    // we're using a sub worker to avoid memory leaks. When memory usage exceeds 90%, we kill the worker and restart it.
+    // this is a temporary solution until we can fix the memory leaks.
+    // the logic for the worker killing itself is in `packages/next/server/lib/start-server.ts`
+    if (!process.env.__NEXT_DISABLE_MEMORY_WATCHER && cluster.isMaster) {
+      cluster.fork()
+      cluster.on('exit', (worker) => {
+        if (worker.exitedAfterDisconnect) {
+          cluster.fork()
+        } else {
+          process.exit(1)
+        }
       })
-      .catch((err) => {
-        if (err.code === 'EADDRINUSE') {
-          let errorMessage = `Port ${port} is already in use.`
-          const pkgAppPath = require('next/dist/compiled/find-up').sync(
-            'package.json',
-            {
-              cwd: dir,
-            }
-          )
-          const appPackage = require(pkgAppPath)
-          if (appPackage.scripts) {
-            const nextScript = Object.entries(appPackage.scripts).find(
-              (scriptLine) => scriptLine[1] === 'next'
+    } else {
+      startServer(devServerOptions)
+        .then(async (app) => {
+          const appUrl = `http://${app.hostname}:${app.port}`
+          startedDevelopmentServer(appUrl, `${host || '0.0.0.0'}:${app.port}`)
+          // Start preflight after server is listening and ignore errors:
+          preflight().catch(() => {})
+          // Finalize server bootup:
+          await app.prepare()
+        })
+        .catch((err) => {
+          if (err.code === 'EADDRINUSE') {
+            let errorMessage = `Port ${port} is already in use.`
+            const pkgAppPath = require('next/dist/compiled/find-up').sync(
+              'package.json',
+              {
+                cwd: dir,
+              }
             )
-            if (nextScript) {
-              errorMessage += `\nUse \`npm run ${nextScript[0]} -- -p <some other port>\`.`
+            const appPackage = require(pkgAppPath)
+            if (appPackage.scripts) {
+              const nextScript = Object.entries(appPackage.scripts).find(
+                (scriptLine) => scriptLine[1] === 'next'
+              )
+              if (nextScript) {
+                errorMessage += `\nUse \`npm run ${nextScript[0]} -- -p <some other port>\`.`
+              }
             }
+            console.error(errorMessage)
+          } else {
+            console.error(err)
           }
-          console.error(errorMessage)
-        } else {
-          console.error(err)
-        }
-        process.nextTick(() => process.exit(1))
-      })
+          process.nextTick(() => process.exit(1))
+        })
+    }
   }
 
   for (const CONFIG_FILE of CONFIG_FILES) {
diff --git a/packages/next/server/lib/start-server.ts b/packages/next/server/lib/start-server.ts
index 4308a93db34fdb2..a84bd90966aa3b5 100644
--- a/packages/next/server/lib/start-server.ts
+++ b/packages/next/server/lib/start-server.ts
@@ -2,17 +2,28 @@ import type { NextServerOptions, NextServer, RequestHandler } from '../next'
 import { warn } from '../../build/output/log'
 import http from 'http'
 import next from '../next'
-
+import cluster from 'cluster'
+import v8 from 'v8'
 interface StartServerOptions extends NextServerOptions {
   allowRetry?: boolean
   keepAliveTimeout?: number
 }
 
+const MAXIMUM_HEAP_SIZE_ALLOWED =
+  (v8.getHeapStatistics().heap_size_limit / 1024 / 1024) * 0.9
+
 export function startServer(opts: StartServerOptions) {
   let requestHandler: RequestHandler
 
   const server = http.createServer((req, res) => {
-    return requestHandler(req, res)
+    return requestHandler(req, res).finally(() => {
+      if (
+        cluster.worker &&
+        process.memoryUsage().heapUsed / 1024 / 1024 > MAXIMUM_HEAP_SIZE_ALLOWED
+      ) {
+        cluster.worker.kill()
+      }
+    })
   })
 
   if (opts.keepAliveTimeout) {