Mirroring traffic to multiple service subsets


I am trying to integrate Istio’s traffic mirroring feature with Spinnaker’s automated canary analysis deployment model; to this end I am deploying a baseline deployment of my application (the same as my production deployment) together with a canary deployment and analysing metrics collected by the two over a period of time to decide whether to promote the canary to production.

To improve the metrics collected, I want to mirror traffic from production to both the baseline and canary, however the only way I can do this is by splitting the traffic between the baseline and canary rather than sending the same traffic to both the baseline and the canary (i.e. mirroring to two service subsets).

Is this possible to achieve with Istio at the moment? Or is there a canary deployment model that would be better to achieve what I want? My SO post on the same issue might provide extra detail.