Backport Bug#45852 Semisynch: Last_IO_Error: Fatal error: Failed to run 'after_queue_event' hook

Errors when send reply to master should never cause the IO thread
to stop, because master can fall back to async replication if it
does not get reply from slave.

The problem is fixed by deliberately ignoring the return value of
slaveReply.

plugin/semisync/semisync_slave_plugin.cc

@@ -99,9 +99,16 @@ int repl_semi_slave_queue_event(Binlog_relay_IO_param *param,
 				uint32 flags)
 {
   if (rpl_semi_sync_slave_status && semi_sync_need_reply)
-    return repl_semisync.slaveReply(param->mysql,
+  {
+    /*
+      We deliberately ignore the error in slaveReply, such error
+      should not cause the slave IO thread to stop, and the error
+      messages are already reported.
+    */
+    (void) repl_semisync.slaveReply(param->mysql,
                                     param->master_log_name,
                                     param->master_log_pos);
+  }
   return 0;
 }