Fine-grained lock service in meta server

[WenyXu]

What problem does the new feature solve?

It ensures correctness during procedures and reduces the lock's scope, making the procedure execution faster.

What does the feature do?

Considers introducing a fine-grained lock service(memory-based) in the meta server's leader. And procedure acquires locks on demand.

The incorrect locking

If we didn't acquire the lock before operating the shared resource, it might incur data inconsistency.

coarse-grained locking

The procedure acquires the coarse-grained lock during the whole procedure. However, if the scope of locks overlaps, procedures are executed serially.

fine-grained locking

Implementation challenges

However, if the old leader loses the leadership(e.g., network partition), its running procedure can still write data into etcd, which also incurs data inconsistency.

[killme2008]

Looks interesting. I wonder what's the plan of this issue. @WenyXu

[WenyXu]

Looks interesting. I wonder what's the plan of this issue. @WenyXu

The fine-grained locks currently have yet to be planned. Let's implement the #3061 first.