Add a mechanism (or document how) to pre-warm the cache

[CAFxX]

There seem to be no way to pre-warm the contents of groupcache at startup. My use-case is described in https://groups.google.com/forum/#!topic/golang-nuts/MweGX6QWNyY but, briefly, is to make sure that after startup my application can process at full speed (this requires groupcache to be fully warmed up) instead of taking 20+ minutes for the empty cache to warm up, during which processing is very slow.

[fiorix]

Isn't it just Get all keys you want pre-loaded?

[CAFxX]

@fiorix that would work in a world (or for the rare scenarios) with no per-operation latencies. My use-case is described in the URL above: if you read that post and think about it, loading all individual keys is what we already do. And it's taking 20+ minutes. With a bulk load operation, we could do the same thing in <30s.

[smyrman]

You could chain the cache...

I.e.:

• A "bulk fetch" Group (cached, Get calls issued at start-up); store items in a data-structure so that individual items can be accessed.
• A "single item fetch" Group (cached, Get not issued at start-up).
• An outer Getter wrapping the two others (with no cache) that:
  1. Get the bulk from the first Group, and extracts the relevant sub-item if present.
  2. Fallback to retrieve the item from the single-item Group.

If relevant, the outer Getter could also provide key versioning or expiry emulation by appending content to a section of the key that the underlying Getters ignores, but that's off topic.