net: create diagnostics channels lazily

PR-URL: #38905
Refs: #35711
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

Author: joyeecheung

lib/net.js

@@ -134,6 +134,22 @@ const isWindows = process.platform === 'win32';
 const noop = () => {};
 
 const kPerfHooksNetConnectContext = Symbol('kPerfHooksNetConnectContext');
+
+let netClientSocketChannel;
+let netServerSocketChannel;
+function lazyChannels() {
+  // TODO(joyeecheung): support diagnostics channels in the snapshot.
+  // For now it is fine to create them lazily when there isn't a snapshot to
+  // build. If users need the channels they would have to create them first
+  // before invoking any built-ins that would publish to these channels
+  // anyway.
+  if (netClientSocketChannel === undefined) {
+    const dc = require('diagnostics_channel');
+    netClientSocketChannel = dc.channel('net.client.socket');
+    netServerSocketChannel = dc.channel('net.server.socket');
+  }
+}
+
 const {
   hasObserver,
   startPerf,
@@ -205,7 +221,7 @@ function connect(...args) {
   const options = normalized[0];
   debug('createConnection', normalized);
   const socket = new Socket(options);
-
+  lazyChannels();
   if (options.timeout) {
     socket.setTimeout(options.timeout);
   }
@@ -1737,6 +1753,7 @@ function onconnection(err, clientHandle) {
 
   DTRACE_NET_SERVER_CONNECTION(socket);
   self.emit('connection', socket);
+  lazyChannels();
 }
 
 /**