Add otel instrumentation

lib/src/client.dart

@@ -15,8 +15,10 @@
 import 'dart:async';
 
 import 'dart:js';
+import 'dart:js_util' as js_util;
 
 import 'package:js/js.dart';
+import 'package:opentelemetry/api.dart';
 import 'package:w_common/disposable_browser.dart';
 
 import 'package:sockjs_client_wrapper/src/events.dart';
@@ -53,6 +55,16 @@ class SockJSClient extends Disposable {
   final StreamController<SockJSOpenEvent> _onOpenController =
       StreamController<SockJSOpenEvent>.broadcast();
 
+  /// Context used to capture open and close events while establishing the
+  /// initial connection.
+  ///
+  /// This value is set to the current context during construction, then set to
+  /// root after the first open or close event. This is to correlate events
+  /// related to initial connection with the construction of this object without
+  /// creating long running traces due to events from much further along in the
+  /// sessions lifetime.
+  Context _context;
+
   /// Constructs a new [SockJSClient] that will attempt to connect to a SockJS
   /// server at the given [uri].
   ///
@@ -70,7 +82,7 @@ class SockJSClient extends Disposable {
   ///     final options = new SockJSOptions(
   ///         transports: ['websocket', 'xhr-streaming', 'xhr-polling']);
   ///     final client = new SockJSClient(uri, options: options);
-  SockJSClient(Uri uri, {SockJSOptions? options}) {
+  SockJSClient(Uri uri, {SockJSOptions? options}) : _context = Context.current {
     try {
       _jsClient = js_interop.SockJS(uri.toString(), null, options?._toJs());
       // ignore: avoid_catches_without_on_clauses
@@ -117,6 +129,8 @@ class SockJSClient extends Disposable {
   /// The event will include the selected transport as well as the server URL.
   Stream<SockJSOpenEvent> get onOpen => _onOpenController.stream;
 
+  num get timeout => js_util.getProperty(_jsClient, '_timeout');
+
   /// Close this client.
   ///
   /// Optionally, a [closeCode] and [reason] can be provided.
@@ -153,6 +167,13 @@ class SockJSClient extends Disposable {
   }
 
   void _onClose(js_interop.SockJSCloseEvent event) {
+    spanFromContext(_context).addEvent('sockjs.close', attributes: [
+      Attribute.fromString('sockjs.transport', _jsClient.transport),
+      Attribute.fromDouble('sockjs.timeout', timeout.toDouble()),
+      Attribute.fromInt('sockjs.close.code', event.code),
+      Attribute.fromString('sockjs.close.reason', event.reason),
+    ]);
+    _context = Context.root; // Reset context to root for future events.
     _onCloseController.add(SockJSCloseEvent(
       event.code,
       event.reason,
@@ -165,6 +186,11 @@ class SockJSClient extends Disposable {
   }
 
   void _onOpen(_) {
+    spanFromContext(_context).addEvent('sockjs.open', attributes: [
+      Attribute.fromString('sockjs.transport', _jsClient.transport),
+      Attribute.fromDouble('sockjs.timeout', timeout.toDouble()),
+    ]);
+    _context = Context.root; // Reset context to root for future events.
     _onOpenController.add(SockJSOpenEvent(
       _jsClient.transport,
       Uri.parse(_jsClient.url),

pubspec.yaml

@@ -9,6 +9,7 @@ environment:
 dependencies:
   js: ^0.6.1
   w_common: '>=2.0.0 <4.0.0'
+  opentelemetry: ^0.18.10
 
 dev_dependencies:
   build_runner: ^2.1.2

test/sockjs_client_wrapper_test.dart

@@ -96,6 +96,12 @@ void main() {
       client.close();
       await Future.wait([client.onClose.first, client.didDispose]);
     });
+
+    test('timeout option should set a timeout', () async {
+      final options = SockJSOptions(timeout: 1000);
+      final client = SockJSClient(_echoUri, options: options)..close();
+      expect(client.timeout, equals(1000));
+    });
   });
 }