src: support diagnostics channel in the snapshot

lib/internal/main/mksnapshot.js

@@ -48,7 +48,7 @@ const supportedModules = new SafeSet(new SafeArrayIterator([
   'constants',
   'crypto',
   // 'dgram',
-  // 'diagnostics_channel',
+  'diagnostics_channel',
   // 'dns',
   // 'dns/promises',
   // 'domain',
@@ -60,7 +60,7 @@ const supportedModules = new SafeSet(new SafeArrayIterator([
   // 'https',
   // 'inspector',
   // 'module',
-  // 'net',
+  'net',
   'os',
   'path',
   'path/posix',

lib/net.js

@@ -131,20 +131,9 @@ 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 dc = require('diagnostics_channel');
+const netClientSocketChannel = dc.channel('net.client.socket');
+const netServerSocketChannel = dc.channel('net.server.socket');
 
 const {
   hasObserver,
@@ -217,7 +206,7 @@ function connect(...args) {
   const options = normalized[0];
   debug('createConnection', normalized);
   const socket = new Socket(options);
-  lazyChannels();
+
   if (netClientSocketChannel.hasSubscribers) {
     netClientSocketChannel.publish({
       socket,
@@ -1761,7 +1750,6 @@ function onconnection(err, clientHandle) {
   socket.server = self;
   socket._server = self;
   self.emit('connection', socket);
-  lazyChannels();
   if (netServerSocketChannel.hasSubscribers) {
     netServerSocketChannel.publish({
       socket,

test/fixtures/snapshot/server.js

@@ -0,0 +1,60 @@
+'use strict';
+
+const net = require('net');
+const {
+  setDeserializeMainFunction
+} = require('v8').startupSnapshot;
+const dc = require('diagnostics_channel');
+
+const echoServer = net.Server(function(connection) {
+  connection.on('data', function(chunk) {
+    connection.write(chunk);
+  });
+  connection.on('end', function() {
+    connection.end();
+  });
+});
+
+const kNumChars = 256;
+const buffer = new Uint8Array(kNumChars);
+for (let i = 0; i < kNumChars; ++i) {
+  buffer[i] = i;
+}
+
+let recv = '';
+
+echoServer.on('listening', function() {
+  const port = this.address().port;
+  console.log(`server port`, port);
+  const c = net.createConnection({ host: '127.0.0.1', port });
+
+  c.on('data', function(chunk) {
+    recv += chunk.toString('latin1');
+
+    if (recv.length === buffer.length) {
+      c.end();
+    }
+  });
+
+  c.on('connect', function() {
+    c.write(buffer);
+  });
+
+  c.on('close', function() {
+    console.log(`recv.length: ${recv.length}`);
+    echoServer.close();
+  });
+
+});
+
+dc.subscribe('net.server.socket', (({ socket }) => {
+  console.log(`From server diagnostics channel:`, socket.localPort);
+}));
+
+dc.subscribe('net.client.socket', (({ socket }) => {
+  console.log(`From client diagnostics channel`);
+}));
+
+setDeserializeMainFunction(() => {
+  echoServer.listen(0);
+});

test/parallel/test-bootstrap-modules.js

@@ -46,6 +46,7 @@ const expectedModules = new Set([
   'Internal Binding wasm_web_api',
   'Internal Binding worker',
   'NativeModule buffer',
+  'NativeModule diagnostics_channel',
   'NativeModule events',
   'NativeModule fs',
   'NativeModule internal/abort_controller',

test/parallel/test-snapshot-net.js

@@ -0,0 +1,65 @@
+'use strict';
+
+// This tests that a local TCP server can be snapshotted and the
+// diagnostics channels work across serialization.
+
+require('../common');
+const assert = require('assert');
+const { spawnSync } = require('child_process');
+const tmpdir = require('../common/tmpdir');
+const fixtures = require('../common/fixtures');
+const path = require('path');
+const fs = require('fs');
+
+tmpdir.refresh();
+const blobPath = path.join(tmpdir.path, 'snapshot.blob');
+const entry = fixtures.path('snapshot', 'server.js');
+{
+  const child = spawnSync(process.execPath, [
+    '--snapshot-blob',
+    blobPath,
+    '--build-snapshot',
+    entry,
+  ], {
+    cwd: tmpdir.path
+  });
+  if (child.status !== 0) {
+    console.log(child.stderr.toString());
+    console.log(child.stdout.toString());
+    assert.strictEqual(child.status, 0);
+  }
+  const stats = fs.statSync(path.join(tmpdir.path, 'snapshot.blob'));
+  assert(stats.isFile());
+}
+
+{
+  const child = spawnSync(process.execPath, [
+    '--snapshot-blob',
+    blobPath,
+  ], {
+    cwd: tmpdir.path,
+    env: {
+      ...process.env,
+    }
+  });
+
+  const stdout = child.stdout.toString().trim();
+  console.log(`[stdout]:\n${stdout}\n`);
+  const stderr = child.stderr.toString().trim();
+  console.log(`[stderr]:\n${stderr}\n`);
+  assert.strictEqual(child.status, 0);
+
+  const lines = stdout.split('\n');
+  assert.strictEqual(lines.length, 4);
+
+  // The log should look like this:
+  // server port ${port}
+  // From client diagnostics channel
+  // From server diagnostics channel: ${port}
+  // recv.length: 256
+  assert.match(lines[0], /server port (\d+)/);
+  const port = lines[0].match(/server port (\d+)/)[1];
+  assert.match(lines[1], /From client diagnostics channel/);
+  assert.match(lines[2], new RegExp(`From server diagnostics channel: ${port}`));
+  assert.match(lines[3], /recv\.length: 256/);
+}