http: add diagnostics channel for http client

Author: theanarkh

doc/api/diagnostics_channel.md

@@ -307,6 +307,37 @@ channel.subscribe(onMessage);
 channel.unsubscribe(onMessage);
 ```
 
+### Built-in Channels
+
+#### HTTP
+
+`http.client.request.start`: Emited with arguments `request` when client
+starts a request.
+
+* `request` {http.ClientRequest}
+
+`http.client.response.finish`: Emited with arguments `request`, `response`
+when client receives a response.
+
+* `request` {http.ClientRequest}
+* `response` {http.IncomingMessage}
+
+`http.server.request.start`: Emited with arguments `request`, `response`,
+`socket`, `server` when server receives a request.
+
+* `request` {http.IncomingMessage}
+* `response` {http.ServerResponse}
+* `socket` {net.Socket}
+* `server` {http.Server}
+
+`http.server.response.finish`: Emited with arguments `request`, `response`,
+`socket`, `server` when server sends a response.
+
+* `request` {http.IncomingMessage}
+* `response` {http.ServerResponse}
+* `socket` {net.Socket}
+* `server` {http.Server}
+
 [`'uncaughtException'`]: process.md#event-uncaughtexception
 [`channel.subscribe(onMessage)`]: #channelsubscribeonmessage
 [`diagnostics_channel.channel(name)`]: #diagnostics_channelchannelname

lib/_http_client.js

@@ -90,6 +90,10 @@ const {
 
 const kClientRequestStatistics = Symbol('ClientRequestStatistics');
 
+const dc = require('diagnostics_channel');
+const onClientRequestStartChannel = dc.channel('http.client.request.start');
+const onClientResponseFinishChannel = dc.channel('http.client.response.finish');
+
 const { addAbortSignal, finished } = require('stream');
 
 let debug = require('internal/util/debuglog').debuglog('http', (fn) => {
@@ -367,6 +371,11 @@ ClientRequest.prototype._finish = function _finish() {
       },
     });
   }
+  if (onClientRequestStartChannel.hasSubscribers) {
+    onClientRequestStartChannel.publish({
+      request: this,
+    });
+  }
 };
 
 ClientRequest.prototype._implicitHeader = function _implicitHeader() {
@@ -645,6 +654,12 @@ function parserOnIncomingClient(res, shouldKeepAlive) {
       },
     });
   }
+  if (onClientResponseFinishChannel.hasSubscribers) {
+    onClientResponseFinishChannel.publish({
+      request: req,
+      response: res,
+    });
+  }
   req.res = res;
   res.req = req;
 

test/parallel/test-diagnostics-channel-http.js

@@ -0,0 +1,63 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const http = require('http');
+const net = require('net');
+const dc = require('diagnostics_channel');
+
+const onClientRequestStart = dc.channel('http.client.request.start');
+const onClientResponseFinish = dc.channel('http.client.response.finish');
+const onServerRequestStart = dc.channel('http.server.request.start');
+const onServerResponseFinish = dc.channel('http.server.response.finish');
+
+const isHTTPServer = (server) => server instanceof http.Server;
+const isIncomingMessage = (object) => object instanceof http.IncomingMessage;
+const isOutgoingMessage = (object) => object instanceof http.OutgoingMessage;
+const isNetSocket = (socket) => socket instanceof net.Socket;
+
+onClientRequestStart.subscribe(common.mustCall(({ request }) => {
+  assert.strictEqual(isOutgoingMessage(request), true);
+}));
+
+onClientResponseFinish.subscribe(common.mustCall(({ request, response }) => {
+  assert.strictEqual(isOutgoingMessage(request), true);
+  assert.strictEqual(isIncomingMessage(response), true);
+}));
+
+onServerRequestStart.subscribe(common.mustCall(({
+  request,
+  response,
+  socket,
+  server,
+}) => {
+  assert.strictEqual(isIncomingMessage(request), true);
+  assert.strictEqual(isOutgoingMessage(response), true);
+  assert.strictEqual(isNetSocket(socket), true);
+  assert.strictEqual(isHTTPServer(server), true);
+}));
+
+onServerResponseFinish.subscribe(common.mustCall(({
+  request,
+  response,
+  socket,
+  server,
+}) => {
+  assert.strictEqual(isIncomingMessage(request), true);
+  assert.strictEqual(isOutgoingMessage(response), true);
+  assert.strictEqual(isNetSocket(socket), true);
+  assert.strictEqual(isHTTPServer(server), true);
+}));
+
+const server = http.createServer(common.mustCall((req, res) => {
+  res.end('done');
+}));
+
+server.listen(() => {
+  const { port } = server.address();
+  http.get(`http://localhost:${port}`, (res) => {
+    res.resume();
+    res.on('end', () => {
+      server.close();
+    });
+  });
+});