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

Signed-off-by: Darshan Sen <raisinten@gmail.com>
PR-URL: https://github.com/nodejs/node/pull/58390
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

doc/api/diagnostics_channel.md

@@ -1239,6 +1239,13 @@ Emitted when a stream is received on the client.
 Emitted when a stream is closed on the client. The HTTP/2 error code used when
 closing the stream can be retrieved using the `stream.rstCode` property.
 
+`http2.server.stream.created`
+
+* `stream` {ServerHttp2Stream}
+* `headers` {HTTP/2 Headers Object}
+
+Emitted when a stream is created on the server.
+
 #### Modules
 
 > Stability: 1 - Experimental

lib/internal/http2/core.js

@@ -190,6 +190,7 @@ const onClientStreamStartChannel = dc.channel('http2.client.stream.start');
 const onClientStreamErrorChannel = dc.channel('http2.client.stream.error');
 const onClientStreamFinishChannel = dc.channel('http2.client.stream.finish');
 const onClientStreamCloseChannel = dc.channel('http2.client.stream.close');
+const onServerStreamCreatedChannel = dc.channel('http2.server.stream.created');
 
 let debug = require('internal/util/debuglog').debuglog('http2', (fn) => {
   debug = fn;
@@ -367,6 +368,12 @@ function onSessionHeaders(handle, id, cat, flags, headers, sensitiveHeaders) {
     if (type === NGHTTP2_SESSION_SERVER) {
       // eslint-disable-next-line no-use-before-define
       stream = new ServerHttp2Stream(session, handle, id, {}, obj);
+      if (onServerStreamCreatedChannel.hasSubscribers) {
+        onServerStreamCreatedChannel.publish({
+          stream,
+          headers: obj,
+        });
+      }
       if (endOfStream) {
         stream.push(null);
       }
@@ -2835,6 +2842,13 @@ class ServerHttp2Stream extends Http2Stream {
       stream[kState].flags |= STREAM_FLAGS_HEAD_REQUEST;
 
     process.nextTick(callback, null, stream, headers, 0);
+
+    if (onServerStreamCreatedChannel.hasSubscribers) {
+      onServerStreamCreatedChannel.publish({
+        stream,
+        headers,
+      });
+    }
   }
 
   // Initiate a response on this Http2Stream

test/parallel/test-diagnostics-channel-http2-server-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.server.stream.created' channel when
+// ServerHttp2Streams are created by both:
+// - in response to an incoming 'stream' event from the client
+// - the server calling ServerHttp2Stream#pushStream()
+
+const Countdown = require('../common/countdown');
+const assert = require('assert');
+const dc = require('diagnostics_channel');
+const http2 = require('http2');
+const { Duplex } = require('stream');
+
+const serverHttp2StreamCreationCount = 2;
+
+dc.subscribe('http2.server.stream.created', common.mustCall(({ stream, headers }) => {
+  // Since ServerHttp2Stream is not exported from any module, this just checks
+  // if the stream is an instance of Duplex and the constructor name is
+  // 'ServerHttp2Stream'.
+  assert.ok(stream instanceof Duplex);
+  assert.strictEqual(stream.constructor.name, 'ServerHttp2Stream');
+  assert.ok(headers && !Array.isArray(headers) && typeof headers === 'object');
+}, serverHttp2StreamCreationCount));
+
+const server = http2.createServer();
+server.on('stream', common.mustCall((stream) => {
+  stream.respond();
+  stream.end();
+
+  stream.pushStream({}, common.mustSucceed((pushStream) => {
+    pushStream.respond();
+    pushStream.end();
+  }));
+}));
+
+server.listen(0, common.mustCall(() => {
+  const port = server.address().port;
+  const client = http2.connect(`http://localhost:${port}`);
+
+  const countdown = new Countdown(serverHttp2StreamCreationCount, () => {
+    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();
+    }));
+  }));
+}));