Internal KeySet Cache

Problem

When doing kdbGet() possible more keys are returned which might be confusing. When doing a second kdbGet() with a new keyset no keys might be returned, because it is up-to-date.

When doing kdbSet() a deep duplication is needed.

Idea: keep a duplicated keyset internally. Return (non-deep?) duplications exactly of the parts as requested.

Constraints

Assumptions

Considered Alternatives

• no cache (current situation)
• flat cache with COW
• deep duplicated cache
• Use global plugin to implement internal cache.
• Use global mmap plugin and make kdbGet() to always retrieve everything.

Decision

Not yet decided.

Rationale

Semantics can be provided without additional code or overhead in the core.

Implications

Related Decisions

• Global Validation

Notes

internal caches lead to duplication of memory consumption (most of it is avoided by reference counting, though)

in some cases caches cannot be avoided? -> filesys, databases?

Cache Discussion

Pros:

• not more keys than needed
• kdbGet avoids IO even if done somewhere else
• KDB handles could be more locally

Cons:

• not possible to access cache with current architecture, KDB high level API
• implementation overhead
• where should the caches be