http2: add diagnostics_channel for client session and streams

lib/internal/http2/core.js

@@ -46,6 +46,12 @@
 const tls = require('tls');
 const { setImmediate, setTimeout, clearTimeout } = require('timers');
 
+const dc = require('diagnostics_channel');
+const onClientSessionCreatedChannel = dc.channel('http2.client.session.created');
+const onClientSessionFinishChannel = dc.channel('http2.client.session.finish');
+const onClientStreamCreatedChannel = dc.channel('http2.client.stream.created');
+const onClientStreamFinishChannel = dc.channel('http2.client.stream.finish');
+
 const {
   kIncomingMessage,
   _checkIsHttpToken: checkIsHttpToken,
@@ -1183,6 +1189,12 @@
   state.flags |= SESSION_FLAGS_DESTROYED;
   state.destroyCode = code;
 
+  if (session instanceof ClientHttp2Session && onClientSessionFinishChannel.hasSubscribers) {
+    onClientSessionFinishChannel.publish({
+      session: session,
+    });
+  }
+
   // Clear timeout and remove timeout listeners.
   session.setTimeout(0);
   session.removeAllListeners('timeout');
@@ -1872,6 +1884,13 @@
     } else {
       onConnect();
     }
+
+    if (onClientStreamCreatedChannel.hasSubscribers) {
+      onClientStreamCreatedChannel.publish({
+        stream: stream,
+      });
+    }
+
     return stream;
   }
 }
@@ -1968,6 +1987,12 @@
     stream.end();
   }
 
+  if (stream instanceof ClientHttp2Stream && onClientStreamFinishChannel.hasSubscribers) {
+    onClientStreamFinishChannel.publish({
+      stream: stream,
+    });
+  }
+
   if (rstStreamStatus !== kNoRstStream) {
     const finishFn = finishCloseStream.bind(stream, code);
     if (!ending || stream.writableFinished || code !== NGHTTP2_NO_ERROR ||
@@ -3399,6 +3424,12 @@
   if (typeof listener === 'function')
     session.once('connect', listener);
 
+  if (onClientSessionCreatedChannel.hasSubscribers) {
+    onClientSessionCreatedChannel.publish({
+      session: session,
+    });
+  }
+
   return session;
 }