http2: add diagnostics channel 'http2.client.stream.created'

Signed-off-by: Darshan Sen <raisinten@gmail.com>
PR-URL: https://github.com/nodejs/node/pull/58246
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
Reviewed-By: Paolo Insogna <paolo@cowtech.it>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>

doc/api/diagnostics_channel.md

@@ -1201,6 +1201,15 @@ The event is emitted before the response is sent.
 
 Emitted when server sends a response.
 
+#### HTTP/2
+
+`http2.client.stream.created`
+
+* `stream` {ClientHttp2Stream}
+* `headers` {HTTP/2 Headers Object}
+
+Emitted when a stream is created on the client.
+
 #### Modules
 
 `module.require.start`

lib/internal/http2/core.js

@@ -183,6 +183,10 @@ const { UV_EOF } = internalBinding('uv');
 
 const { StreamPipe } = internalBinding('stream_pipe');
 const { _connectionListener: httpConnectionListener } = http;
+
+const dc = require('diagnostics_channel');
+const onClientStreamCreatedChannel = dc.channel('http2.client.stream.created');
+
 let debug = require('internal/util/debuglog').debuglog('http2', (fn) => {
   debug = fn;
 });
@@ -371,6 +375,12 @@ function onSessionHeaders(handle, id, cat, flags, headers, sensitiveHeaders) {
     } else {
       // eslint-disable-next-line no-use-before-define
       stream = new ClientHttp2Stream(session, handle, id, {});
+      if (onClientStreamCreatedChannel.hasSubscribers) {
+        onClientStreamCreatedChannel.publish({
+          stream,
+          headers: obj,
+        });
+      }
       if (endOfStream) {
         stream.push(null);
       }
@@ -1863,6 +1873,14 @@ class ClientHttp2Session extends Http2Session {
     } else {
       onConnect();
     }
+
+    if (onClientStreamCreatedChannel.hasSubscribers) {
+      onClientStreamCreatedChannel.publish({
+        stream,
+        headers: headersParam,
+      });
+    }
+
     return stream;
   }
 }

test/parallel/test-diagnostics-channel-http2-client-stream-created.js

@@ -0,0 +1,60 @@
+'use strict';
+
+const common = require('../common');
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+
+// This test ensures that the built-in HTTP/2 diagnostics channels are reporting
+// the diagnostics messages for the 'http2.client.stream.created' channel when
+// ClientHttp2Streams are created by both:
+// - the client calling ClientHttp2Session#request()
+// - in response to an incoming 'push' event from the server
+
+const Countdown = require('../common/countdown');
+const assert = require('assert');
+const dc = require('diagnostics_channel');
+const http2 = require('http2');
+const { Duplex } = require('stream');
+
+const clientHttp2StreamCreationCount = 2;
+
+dc.subscribe('http2.client.stream.created', common.mustCall(({ stream, headers }) => {
+  // Since ClientHttp2Stream is not exported from any module, this just checks
+  // if the stream is an instance of Duplex and the constructor name is
+  // 'ClientHttp2Stream'.
+  assert.ok(stream instanceof Duplex);
+  assert.strictEqual(stream.constructor.name, 'ClientHttp2Stream');
+  assert.ok(headers && !Array.isArray(headers) && typeof headers === 'object');
+}, clientHttp2StreamCreationCount));
+
+const server = http2.createServer();
+server.on('stream', common.mustCall((stream) => {
+  stream.respond();
+  stream.end();
+
+  stream.pushStream({}, common.mustSucceed((pushStream) => {
+    pushStream.respond();
+    pushStream.end();
+  }, 1));
+}, 1));
+
+server.listen(0, common.mustCall(() => {
+  const port = server.address().port;
+  const client = http2.connect(`http://localhost:${port}`);
+
+  const countdown = new Countdown(clientHttp2StreamCreationCount, () => {
+    client.close();
+    server.close();
+  });
+
+  const stream = client.request({});
+  stream.on('response', common.mustCall(() => {
+    countdown.dec();
+  }));
+
+  client.on('stream', common.mustCall((pushStream) => {
+    pushStream.on('push', common.mustCall(() => {
+      countdown.dec();
+    }, 1));
+  }, 1));
+}, 1));