Traffic mirroring is a pre-stage for canary deployments. When mirroring
is enabled, at the beginning of a canary deployment traffic is mirrored
to the canary instead of shifted for one canary period. The service
mesh should mirror by copying the request and sending one copy to the
primary and one copy to the canary; only the response from the primary
is sent to the user. The response from the canary is only used for
collecting metrics.
Once the mirror period is over, the canary proceeds as usual, shifting
traffic from primary to canary until complete.
Added TestScheduler_Mirroring unit test.
SetupMocks() currently takes a bool switch that tells it to configure
against either a shifting canary or an A-B canary. I'll need a third
canary that has mirroring turned on so I changed this to an interface
that just takes the canary to configure (and configs the default
shifting canary if you pass nil).
If port discovery is enabled, Flagger scans the deployment pod template and extracts the container ports excluding the port specified in the canary service spec and Istio proxy ports. All the extra ports will be used when generation the ClusterIP services.
