Support for request hedging

[utahta]

Describe the feature request

Envoy supports request hedging, which can reduce tail latency, from v1.11.0, but it looks like Istio doesn't support to generate such Envoy configuration.

Could this be supported?

Maybe related to https://github.com/istio/istio/issues/2857

[maxenglander]

I am also interested in this, would like to have this issue reopened. Thanks!

[Temikus]

Same here. Google is very eager to recommend request hedging to customers, e.g.: https://cloud.google.com/storage/docs/best-practices

Thus it would make a lot of sense if Istio supported it.

[Bennett-Lynch]

Also interested in this feature. Hedging can drastically reduce high-tail latency. Would like to be able to manage this with Istio rather than at the application layer.

[kaiburjack]

We are also interested in this. Currently, we workaround the missing Istio-native configuration via an EnvoyFilter. (here a working filter installed on the sidecar for "Service A" for calls to "Service B"):

apiVersion: networking.istio.io/v1alpha3
kind: EnvoyFilter
metadata:
  name: service-a-to-b-req-hedging
spec:
  workloadSelector:
    labels:
      app: service-a
  configPatches:
    - applyTo: VIRTUAL_HOST
      match:
        context: SIDECAR_OUTBOUND
        routeConfiguration:
          vhost:
            name: service-b.default.svc.cluster.local:80
      patch:
        operation: MERGE
        value:
          hedge_policy:
            hedge_on_per_try_timeout: true