test: refactor worker/operation and support Delete operation

[ahrtr]

1. Simplify the worker to make it more generic, and can execute different operations;
2. Support Delete operation

[ahrtr]

cc @mitake @ptabor @serathius @spzala @cenkalti

[ahrtr]

cc @tjungblu

[serathius]

Comment above.

[ahrtr]

Comment above.

Resolved. PTAL

[tjungblu]

lgtm (non-binding). Shall we maybe also add some basic linearizability tests for bbolt?

[serathius]

Looks great! thanks.

[ahrtr]

lgtm (non-binding). Shall we maybe also add some basic linearizability tests for bbolt?

The test case is testing a local library instead of a distributed system, so I don't think it needs test linearizability. FYI. #455 (comment)

[serathius]

FYI Linearizability is property of concurrent objects, not necessarily distributed systems. https://jepsen.io/consistency/models/linearizable. You can apply it to any concurrent primitive, including semaphores, locks, concurrent maps and transaction key-value stores like bbolt.

[tjungblu]

Linearizability is property of concurrent objects.

Exactly, a distributed system is not that much different than the concurrency on your multi-core CPU.

I don't think it needs test linearizability

Somewhat agreed, it's not a strict requirement for bbolt to be linearizable to make etcd linearizable. But does it hurt to add it? Worst case we waste some dev time, best case we find some issue.