Merge pull request #22443 from Avogar/hedged

Remove socket from epoll before cancelling packet receiver in HedgedConnections to prevent possible race

src/Client/HedgedConnections.cpp

@@ -521,14 +521,17 @@ void HedgedConnections::processNewReplicaState(HedgedConnectionsFactory::State s
 
 void HedgedConnections::finishProcessReplica(ReplicaState & replica, bool disconnect)
 {
+    /// It's important to remove file descriptor from epoll exactly before cancelling packet_receiver,
+    /// because otherwise another thread can try to receive a packet, get this file descriptor
+    /// from epoll and resume cancelled packet_receiver.
+    epoll.remove(replica.packet_receiver->getFileDescriptor());
+    epoll.remove(replica.change_replica_timeout.getDescriptor());
+
     replica.packet_receiver->cancel();
     replica.change_replica_timeout.reset();
 
-    epoll.remove(replica.packet_receiver->getFileDescriptor());
     --offset_states[fd_to_replica_location[replica.packet_receiver->getFileDescriptor()].offset].active_connection_count;
     fd_to_replica_location.erase(replica.packet_receiver->getFileDescriptor());
-
-    epoll.remove(replica.change_replica_timeout.getDescriptor());
     timeout_fd_to_replica_location.erase(replica.change_replica_timeout.getDescriptor());
 
     --active_connection_count;