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

Signed-off-by: Darshan Sen <raisinten@gmail.com>

Author: RaisinTen

doc/api/diagnostics_channel.md

@@ -1217,6 +1217,13 @@ Emitted when a stream is created on the client.
 
 Emitted when a stream is started on the client.
 
+`http2.client.stream.error`
+
+* `stream` {ClientHttp2Stream}
+* `error` {Error}
+
+Emitted when an error occurs during the processing of a stream on the client.
+
 #### Modules
 
 > Stability: 1 - Experimental

lib/internal/http2/core.js

@@ -187,6 +187,7 @@ const { _connectionListener: httpConnectionListener } = http;
 const dc = require('diagnostics_channel');
 const onClientStreamCreatedChannel = dc.channel('http2.client.stream.created');
 const onClientStreamStartChannel = dc.channel('http2.client.stream.start');
+const onClientStreamErrorChannel = dc.channel('http2.client.stream.error');
 
 let debug = require('internal/util/debuglog').debuglog('http2', (fn) => {
   debug = fn;
@@ -2424,6 +2425,14 @@ class Http2Stream extends Duplex {
     setImmediate(() => {
       session[kMaybeDestroy]();
     });
+    if (err &&
+        session[kType] === NGHTTP2_SESSION_CLIENT &&
+        onClientStreamErrorChannel.hasSubscribers) {
+      onClientStreamErrorChannel.publish({
+        stream: this,
+        error: err,
+      });
+    }
     callback(err);
   }
   // The Http2Stream can be destroyed if it has closed and if the readable

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

@@ -0,0 +1,46 @@
+'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.error' channel when
+// an error occurs during the processing of a ClientHttp2Stream.
+
+const assert = require('assert');
+const dc = require('diagnostics_channel');
+const http2 = require('http2');
+const { Duplex } = require('stream');
+
+dc.subscribe('http2.client.stream.error', common.mustCall(({ stream, error }) => {
+  // 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.strictEqual(stream.closed, true);
+  assert.strictEqual(stream.destroyed, true);
+
+  assert.ok(error);
+  assert.strictEqual(error.code, 'ABORT_ERR');
+  assert.strictEqual(error.name, 'AbortError');
+}));
+
+const server = http2.createServer();
+server.listen(0, common.mustCall(() => {
+  const port = server.address().port;
+  const client = http2.connect(`http://localhost:${port}`);
+
+  const ac = new AbortController();
+  const stream = client.request({}, { signal: ac.signal });
+  ac.abort();
+
+  stream.on('error', common.mustCall((err) => {
+    assert.strictEqual(err.code, 'ABORT_ERR');
+    assert.strictEqual(err.name, 'AbortError');
+
+    client.close();
+    server.close();
+  }));
+}));