fix: gracefully shutdown standalone server

- Both the standalone server and the startServer function it calls
  attempt to stop the server on SIGINT and SIGTERM in different ways.
  This lets server.js yield to startServer
- The cleanup function in startServer was not waiting for the server to
  close before calling process.exit. This lets it wait for any in-flight
  requests to finish processing before exiting the process

fixes: vercel#53661

packages/next/src/build/utils.ts

@@ -2026,13 +2026,6 @@ const dir = path.join(__dirname)
 process.env.NODE_ENV = 'production'
 process.chdir(__dirname)
 
-// Make sure commands gracefully respect termination signals (e.g. from Docker)
-// Allow the graceful termination to be manually configurable
-if (!process.env.NEXT_MANUAL_SIG_HANDLE) {
-  process.on('SIGTERM', () => process.exit(0))
-  process.on('SIGINT', () => process.exit(0))
-}
-
 const currentPort = parseInt(process.env.PORT, 10) || 3000
 const hostname = process.env.HOSTNAME || '0.0.0.0'
 

packages/next/src/server/lib/start-server.ts

@@ -266,8 +266,9 @@ export async function startServer(
       try {
         const cleanup = (code: number | null) => {
           debug('start-server process cleanup')
-          server.close()
-          process.exit(code ?? 0)
+          server.close(() => {
+            process.exit(code ?? 0)
+          })
         }
         const exception = (err: Error) => {
           if (isPostpone(err)) {