fix(server): cover builder-based manual processor startup

Author: kabir

docs/content/dev/server.md

@@ -266,17 +266,32 @@ class A2AServerConfiguration {
         return new MainEventBusProcessor(mainEventBus, taskStore, pushSender, queueManager);
     }
 
+    @Bean(destroyMethod = "shutdown")
+    ExecutorService a2aEventConsumerExecutor() {
+        return Executors.newCachedThreadPool();
+    }
+
     @Bean
     RequestHandler requestHandler(AgentExecutor agentExecutor, TaskStore taskStore,
                                   QueueManager queueManager, PushNotificationConfigStore pushConfigStore,
                                   MainEventBusProcessor mainEventBusProcessor,
-                                  @Qualifier("a2aInternal") Executor executor) {
-        return new DefaultRequestHandler(agentExecutor, taskStore, queueManager, pushConfigStore,
-                mainEventBusProcessor, executor, executor);
+                                  TaskAuthorizationProvider authorizationProvider,
+                                  @Qualifier("a2aInternalExecutor") Executor executor,
+                                  @Qualifier("a2aEventConsumerExecutor") Executor eventConsumerExecutor) {
+        return DefaultRequestHandler.builder()
+                .agentExecutor(agentExecutor)
+                .taskStore(taskStore)
+                .queueManager(queueManager)
+                .pushConfigStore(pushConfigStore)
+                .mainEventBusProcessor(mainEventBusProcessor)
+                .authorizationProvider(authorizationProvider)
+                .executor(executor)
+                .eventConsumerExecutor(eventConsumerExecutor)
+                .build();
     }
 }
 ```
 
-This assumes the other method parameters are also registered as Spring beans. The same executor is passed for agent execution and event consumption, as in this example; applications can provide separate executors when needed.
+Register the remaining dependencies, including an `a2aInternalExecutor` bean and a `TaskAuthorizationProvider`, as Spring beans. Keep the cached event consumer executor separate from the agent executor: blocking event polling can exhaust a bounded pool under load.
 
 See [CONTRIBUTING_INTEGRATIONS.md](https://github.com/a2aproject/a2a-java/blob/main/CONTRIBUTING_INTEGRATIONS.md) to submit your own integration.

server-common/src/main/java/org/a2aproject/sdk/server/events/MainEventBusProcessor.java

@@ -156,6 +156,9 @@ int pushNotificationChainCount() {
         return pushNotificationChains.size();
     }
 
+    /**
+     * Starts the background processor thread if it is not already running.
+     */
     @SuppressWarnings("NullAway.Init")
     @PostConstruct
     public synchronized void start() {

server-common/src/main/java/org/a2aproject/sdk/server/requesthandlers/DefaultRequestHandler.java

@@ -308,6 +308,10 @@ protected DefaultRequestHandler() {
         this.eventConsumerExecutor = null;
     }
 
+    /**
+     * Constructor used by CDI to create the request handler. Its signature may change between
+     * releases; application code should use {@link #builder()} to configure and create a handler.
+     */
     @Inject
     public DefaultRequestHandler(AgentExecutor agentExecutor, TaskStore taskStore,
                                  QueueManager queueManager, PushNotificationConfigStore pushConfigStore,

server-common/src/test/java/org/a2aproject/sdk/server/requesthandlers/DefaultRequestHandlerTest.java

@@ -187,7 +187,7 @@ void testInitConfigReadsBlockingTimeouts() {
     }
 
     @Test
-    void testConstructorStartsManuallyConstructedMainEventBusProcessor() throws Exception {
+    void testBuilderStartsManuallyConstructedMainEventBusProcessor() throws Exception {
         InMemoryTaskStore manualTaskStore = new InMemoryTaskStore();
         PushNotificationConfigStore manualPushConfigStore = new InMemoryPushNotificationConfigStore();
         MainEventBus manualMainEventBus = new MainEventBus();
@@ -207,9 +207,16 @@ public void cancel(RequestContext context, AgentEmitter agentEmitter) {
                     throw new AssertionError("Cancel should not be invoked");
                 }
             };
-            DefaultRequestHandler manualRequestHandler = new DefaultRequestHandler(
-                manualAgentExecutor, manualTaskStore, manualQueueManager, manualPushConfigStore,
-                manualProcessor, internalExecutor, internalExecutor);
+            DefaultRequestHandler manualRequestHandler = DefaultRequestHandler.builder()
+                    .agentExecutor(manualAgentExecutor)
+                    .taskStore(manualTaskStore)
+                    .queueManager(manualQueueManager)
+                    .pushConfigStore(manualPushConfigStore)
+                    .mainEventBusProcessor(manualProcessor)
+                    .executor(internalExecutor)
+                    .eventConsumerExecutor(internalExecutor)
+                    .authorizationRequired(false)
+                    .build();
             manualRequestHandler.agentCompletionTimeoutSeconds = 5;
             manualRequestHandler.consumptionCompletionTimeoutSeconds = 2;
             manualRequestHandler.reconciliationTimeoutSeconds = 1;