brick_server new client API - sync_wal (per chain)

[tatsuya6502]

I have not figured out what would be the best API set to do this, but I am thinking to add sync_wal operation which is analogue of fsync in file system. (wal: write ahead log, aka common hlog in Hibari)

As of v0.1.x, Hibari has option to specify whether enabling group commit or not only per table level. sync_wal operation (and maybe sync_wal do flag for write operations too) will make it possible to flush OS's dirty write buffer of the common hlog to a stable storage (HDD or SSD) only when necessary.

They might look like:

• sync_wal/3
  • flush dirty write buffer of the common hlog to a disk, on each chain of bricks assigned to binary key prefix(es).
  • sync_wal(table(), key_prefix()|[key_prefix()], timeout())
• do_op_flag sync_wal | {sync_wal, boolean()}
  • flag for a do batch operation.

[tatsuya6502]

No target milestone for now.