Update keepAlive configs (#1266)

* Update keepAlive configs

* comment

Author: grouma

dwds/CHANGELOG.md

@@ -10,6 +10,8 @@
 - Add `DwdsEvent`s around stepping and evaluation.
 - Send an event to the Dart Debug Extension that contains VM service protocol URI. 
 - Depend on `package:vm_service` version `6.1.0+1`.
+- Update the `keepAlive` configs to prevent accidental reuse of a connection after stopping
+  a debug session.
 
 **Breaking changes:**
 - `LoadStrategy`s now require a `moduleInfoForEntrypoint`.

dwds/lib/dwds.dart

@@ -119,7 +119,11 @@ class Dwds {
     if (enableDebugExtension) {
       final handler = useSseForDebugBackend
           ? SseSocketHandler(SseHandler(Uri.parse('/\$debug'),
-              keepAlive: const Duration(seconds: 30)))
+              // Proxy servers may actively kill long standing connections.
+              // Allow for clients to reconnect in a short window. Making the
+              // window too long may cause issues if the user closes a debug
+              // session and initites a new one during the keepAlive window.
+              keepAlive: const Duration(seconds: 2)))
           : WebSocketSocketHandler();
 
       extensionBackend = await ExtensionBackend.start(handler, hostname);

dwds/lib/src/services/debug_service.dart

@@ -230,7 +230,7 @@ class DebugService {
     // DDS will always connect to DWDS via web sockets.
     if (useSse && !spawnDds) {
       var sseHandler = SseHandler(Uri.parse('/$authToken/\$debugHandler'),
-          keepAlive: const Duration(seconds: 30));
+          keepAlive: const Duration(seconds: 2));
       handler = sseHandler.handler;
       unawaited(_handleSseConnections(
           sseHandler, chromeProxyService, serviceExtensionRegistry,