Solution to the periodic slowdown of GetUpdatesSnce

[1522140840]

In my project, I use GetUpdatesSince for master-slave synchronization. I have noticed that the execution time of this method periodically increases, and by examining the source code, it is easy to identify that it is caused by SeekToStartSequence. Essentially, this is due to the periodic enlargement of the WAL (Write-Ahead Log) file. To address this issue, I have made a small optimization in my project. My approach involves adding a new method called GoOnRead to the TransactionLogIterator. As long as the WAL file hasn't switched and there is new data being written, I reset the state of the iterator to be valid. This way, I don't have to frequently reopen the iterator and can read the new data.

The overall time-consuming issue of my master-slave synchronization with TP999 is as follows: [The program itself sleeps for 100ms.]