Missing soft limit on the space's mem table usage

[ShiKaiWi]

Describe This Problem

There is no soft limit over the space/instance's memtable usage in the current write procedure, and the following write requests must be blocked/rejected once the hard limit is reached. In conclusion, write errors will occur immediately when the hard limit of the instance/space's memtable is reached.

Proposal

Introduce the soft limit over the space/instance's memtable usage, and once it is reached, the flush of the largest memtables in the space/instance should be triggered, and the flush should not block the write procedure. Only the hard limit is reached, the following write requests should be rejected.

Additional Context

No response

[ShiKaiWi]

I'll take this ticket.