fix: Correct premature file read termination triggered by sender back…

… pressure (#1251)

Resolved an issue where incomplete file reads were occurring as a result of
reader flush timeout events overwriting blocked events. This fix
ensures that blocked events maintain priority, allowing files to be read fully.

core/event/BlockEventManager.h

@@ -50,7 +50,14 @@ class BlockedEventManager : public LogstoreFeedBackInterface {
         BlockedEvent() : mLogstoreKey(0), mEvent(NULL), mInvalidTime(time(NULL)), mTimeout(1) {}
         void Update(const LogstoreFeedBackKey& logstoreKey, Event* pEvent, int32_t curTime) {
             if (mEvent != NULL) {
-                delete mEvent;
+                // There are only two situations where event coverage is possible
+                // 1. the new event is not timeout event
+                // 2. old event is timeout event
+                if (!pEvent->IsReaderFlushTimeout() || mEvent->IsReaderFlushTimeout()) {
+                    delete mEvent;
+                } else {
+                    return;
+                }
             }
             mEvent = pEvent;
             mLogstoreKey = logstoreKey;