Mixer should deduplicate instances delivered to adapters

[geeknoid]

---------- Forwarded message ---------- From: mtail [email protected] Date: Mon, Jul 31, 2017 at 11:21 AM Subject: Deduping Instances To: Istio Integrations [email protected]

We just had this discussion during the Mixer design review regarding deduping of instances.

After thinking about it for a few minutes, I'm now comfortable stating that we should just systematically be doing this, and in fact we should generalize things are bit.

For a given operation, Mixer should collect all instances that are being sent to a particular handler across all active actions, should deduplicate, and should trigger the minimal number of calls possible to the adapter.

Within the context of a single action, we should statically flag duplicate instances as an error, since it is likely a typo on the operator's part. Across instances, we don't flag errors and merely dedup at runtime.

Does anyone have counter-examples where this wouldn't be appropriate?

[ZackButcher]

I'll tackle this as I'm rewriting config resolution under the new adapter scheme.

[guptasu]

FYI, we are already doing similar thing during the configuration path where we call handlers to pass them inferred types.

All actions are traversed, eventually forming a tree (Handler -> []Templates -> []InferedTypes). We might be able to steal some logic from there. https://github.com/istio/mixer/blob/master/pkg/config/handler.go#L112

Removing myself from assignee

[douglas-reid]

@ZackButcher we should be able to turn it off/on (either globally or per-adapter). i have some thoughts on possible approaches if you are starting on a design doc.