[nodejs] Handle Next.js weblog shutdown telemetry

Author: smola

utils/build/docker/nodejs/nextjs.Dockerfile

@@ -21,6 +21,11 @@ ENV DD_TRACE_HEADER_TAGS=user-agent
 
 # docker startup
 ENV DD_DATA_STREAMS_ENABLED=true
+# Let src/instrumentation.js handle Next.js shutdown signals manually, as documented in:
+# https://nextjs.org/docs/pages/guides/self-hosting#manual-graceful-shutdowns
+# Support was added in https://github.com/vercel/next.js/pull/59117; this
+# weblog is pinned to Next.js >=14.0.4 to support NEXT_MANUAL_SIG_HANDLE.
+ENV NEXT_MANUAL_SIG_HANDLE=true
 ENV PORT=7777
 ENV HOSTNAME=0.0.0.0
 COPY utils/build/docker/nodejs/app.sh app.sh

utils/build/docker/nodejs/nextjs/next.config.js

@@ -3,7 +3,11 @@ const nextConfig = {
   // Disabled because standalone mode does not support using modules directly
   // from node_modules which is necessary when using `npm link dd-trace`.
   // output: 'standalone'
-  outputFileTracing: false
+  outputFileTracing: false,
+  experimental: {
+    // Run out src/instrumentation.js hooks
+    instrumentationHook: true
+  }
 }
 
 module.exports = nextConfig

utils/build/docker/nodejs/nextjs/src/instrumentation.js

@@ -0,0 +1,33 @@
+'use strict'
+
+// Time to wait after invoking dd-trace's beforeExit handlers before forcing
+// the process to exit. The handlers are fire-and-forget (no Promise, no
+// awaitable signal) and initiate asynchronous HTTP exports for telemetry,
+// traces, remote config, AppSec metrics, dogstatsd, etc., so we need a grace
+// window for those in-flight requests to drain. Stays well below docker
+// stop's default 10s SIGKILL timeout.
+const SHUTDOWN_GRACE_MS = 5000
+
+function shutdown () {
+  const ddTrace = globalThis[Symbol.for('dd-trace')]
+
+  if (ddTrace?.beforeExitHandlers) {
+    for (const handler of ddTrace.beforeExitHandlers) {
+      try {
+        handler()
+      } catch (err) {
+        // Best-effort: keep running other handlers even if one throws.
+        console.error('dd-trace beforeExit handler threw', err)
+      }
+    }
+  }
+
+  setTimeout(() => process.exit(0), SHUTDOWN_GRACE_MS).unref()
+}
+
+export function register () {
+  if (!process.env.NEXT_MANUAL_SIG_HANDLE || process.env.NEXT_RUNTIME === 'edge') return
+
+  process.once('SIGINT', shutdown)
+  process.once('SIGTERM', shutdown)
+}