Support asynchronously incrementally sync files to disk while they are being written

[overvenus]

The idea is borrowed from RocksDB bytes_per_sync. It allows asynchronously incrementally sync files to disk while they are being written.
It smoothes out write I/Os over time and reduce fdatasync latency spike as we saw in #346 (comment) .

Note: The feature proposed here is different from the deprecated bytes_per_sync feature which sync file synchronously.

[v0y4g3r]

A similar issue: GreptimeTeam/greptimedb#3085
Currently we use periodical fsync to alleviate the problem.

Before the periodical fsync the disk ioutil looks like:

[LykxSassinator]

THx for your advices. This problems might not be similar to yours. And we've met this problem on Cloud Env when rewriting and fixed it in #347, by introducing bytes_per_sync to limit the maximum flushing bytes. /cc @v0y4g3r

FYI, u can check whether there exists similar syncing problems when rewriting raft logs. And if does, u can check the latest version as your choice.

[v0y4g3r]

THx for your advices. This problems might not be similar to yours. And we've met this problem on Cloud Env when rewriting and fixed it in #347, by introducing bytes_per_sync to limit the maximum flushing bytes. /cc @v0y4g3r

FYI, u can check whether there exists similar syncing problems when rewriting raft logs. And if does, u can check the latest version as your choice.

Do you have any plan to release a new version?

[LykxSassinator]

/cc @overvenus @tabokie PTAL, thx.

We'll do it recently. Before that, u can update your dependency of raft-engine with the latest commit-id.