slow incremental resync speed

[xiaoxichen]

he m_resync_mode is always to false which lead each resync go through general IO path --- we queue the fetch data requests to a queue, the reaper_thread picks from the queue and wait at least 1.5s before fetching data (https://github.com/eBay/HomeStore/blob/13a2def8befe0cc22884fc54f590fadad63d64a3/src/lib/replication/service/raft_repl_service.cpp#L386-L388), this is the root cause of very slow resync.

[JacksonYao287]

we need to put more time on this one, right? it will probabaly impact the performance test

[xiaoxichen]

resolved