[event] suppress expected optimizer drop warnings

Author: Tyndalllll

kv_cache_manager/event/optimizer_event_publisher.cc

@@ -36,8 +36,10 @@ bool OptimizerEventPublisher::Publish(const std::shared_ptr<BaseEvent> &event) {
         return false;
     }
     // Runs on a serving thread: enqueue and return, nothing else. A full queue
-    // drops the event (counted by the base class) rather than blocking.
-    return BasicEnqueue(event);
+    // drops the event (counted by the base class) without surfacing an expected
+    // best-effort drop as a publish failure and triggering a warning per request.
+    BasicEnqueue(event);
+    return true;
 }
 
 bool OptimizerEventPublisher::Stop() {

kv_cache_manager/event/test/optimizer_event_publisher_test.cc

@@ -201,8 +201,9 @@ TEST_F(OptimizerEventPublisherTest, TestSinkRefusalIsNotCountedAsForwarded) {
     EXPECT_EQ(0u, publisher_->ForwardedCount());
 }
 
-// The queue is the boundary that protects serving threads: it must refuse, not
-// grow and not block.
+// The queue is the boundary that protects serving threads: it must drop, not
+// grow and not block. Expected best-effort drops are handled without surfacing
+// a publisher failure to EventManager.
 TEST_F(OptimizerEventPublisherTest, TestFullQueueDropsInsteadOfBlocking) {
     sink_->set_accept(false);
     const auto config = MakePublisherConfig(4);
@@ -211,13 +212,9 @@ TEST_F(OptimizerEventPublisherTest, TestFullQueueDropsInsteadOfBlocking) {
     publisher->InitBasicQueue(config.queue_size());
     publisher->running_ = true;
 
-    int accepted = 0;
     for (int i = 0; i < 50; ++i) {
-        if (publisher->Publish(MakeGetEvent("instance-a", {i}, {1}))) {
-            ++accepted;
-        }
+        EXPECT_TRUE(publisher->Publish(MakeGetEvent("instance-a", {i}, {1})));
     }
-    EXPECT_EQ(4, accepted);
     EXPECT_EQ(46u, publisher->DroppedCount());
     publisher->running_ = false;
 }