Fix Port discovery with multiple port services

[fcantournet]

This fixes issue #263

We actually don't need to specify any ports in the VirtualService
and DestinationRules.
Istio will create clusters/listerners for each named port we have declared in
the kubernetes services and the router can be shared as it operates only on L7 criterias

Also contains a tiny clean-up of imports

k get canaries.flagger.app -o yaml places

    autoscalerRef:
      apiVersion: autoscaling/v2beta1
      kind: HorizontalPodAutoscaler
      name: places
    canaryAnalysis:
      interval: 5s
      maxWeight: 50
      metrics:
      - interval: 1m
        name: request-success-rate
        threshold: 99
      - interval: 1m
        name: request-duration
        threshold: 500
      stepWeight: 10
      threshold: 10
      webhooks:
      - metadata:
          cmd: test places --cleanup
          type: helm
        name: helm test
        timeout: 3m
        type: pre-rollout
        url: http://flagger-helmtester.kube-system/
    progressDeadlineSeconds: 60
    service:
      port: 8080
      portDiscovery: true
      trafficPolicy:
        tls:
          mode: DISABLE
    skipAnalysis: true
    targetRef:
      apiVersion: apps/v1
      kind: Deployment
      name: places

k get destinationrules.networking.istio.io -o yaml

- apiVersion: networking.istio.io/v1alpha3
  kind: DestinationRule
  metadata:
    creationTimestamp: "2019-07-23T16:30:35Z"
    generation: 1
    name: places-canary
    namespace: trip
    ownerReferences:
    - apiVersion: flagger.app/v1alpha3
      blockOwnerDeletion: true
      controller: true
      kind: Canary
      name: places
      uid: 30d633f1-ad67-11e9-a8c3-4201c0a8800a
    resourceVersion: "65133888"
    selfLink: /apis/networking.istio.io/v1alpha3/namespaces/trip/destinationrules/places-canary
    uid: 32f65ab0-ad67-11e9-8566-4201c0a8800b
  spec:
    host: places-canary
    trafficPolicy:
      tls:
        mode: DISABLE
- apiVersion: networking.istio.io/v1alpha3
  kind: DestinationRule
  metadata:
    creationTimestamp: "2019-07-23T16:30:35Z"
    generation: 1
    name: places-primary
    namespace: trip
    ownerReferences:
    - apiVersion: flagger.app/v1alpha3
      blockOwnerDeletion: true
      controller: true
      kind: Canary
      name: places
      uid: 30d633f1-ad67-11e9-a8c3-4201c0a8800a
    resourceVersion: "65133889"
    selfLink: /apis/networking.istio.io/v1alpha3/namespaces/trip/destinationrules/places-primary
    uid: 32f916f2-ad67-11e9-8566-4201c0a8800b
  spec:
    host: places-primary
    trafficPolicy:
      tls:
        mode: DISABLE

k get virtualservices.networking.istio.io -o yaml places

kind: VirtualService
metadata:
  creationTimestamp: "2019-07-23T16:30:36Z"
  generation: 6
  name: places
  namespace: trip
  ownerReferences:
  - apiVersion: flagger.app/v1alpha3
    blockOwnerDeletion: true
    controller: true
    kind: Canary
    name: places
    uid: 30d633f1-ad67-11e9-a8c3-4201c0a8800a
  resourceVersion: "70400304"
  selfLink: /apis/networking.istio.io/v1alpha3/namespaces/trip/virtualservices/places
  uid: 32faef14-ad67-11e9-8566-4201c0a8800b
spec:
  gateways:
  - mesh
  hosts:
  - places
  http:
  - route:
    - destination:
        host: places-primary
      weight: 100
    - destination:
        host: places-canary
      weight: 0

istioctl pc route $(k get pods -l app=synapse-trip -o jsonpath='{.items[0].metadata.name}') --name 8080 -o json

...
                "name": "places.trip.svc.cluster.local:8080",
                "domains": [
                    "places.trip.svc.cluster.local",
                    "places.trip.svc.cluster.local:8080",
                    "places",
                    "places:8080",
                    "places.trip.svc.cluster",
                    "places.trip.svc.cluster:8080",
                    "places.trip.svc",
                    "places.trip.svc:8080",
                    "places.trip",
                    "places.trip:8080",
                    "10.250.134.101",
                    "10.250.134.101:8080"
                ],
                "routes": [
                    {
                        "match": {
                            "prefix": "/"
                        },
                        "route": {
                            "cluster": "outbound|8080||places-primary.trip.svc.cluster.local",
...

istioctl pc route $(k get pods -l app=synapse-trip -o jsonpath='{.items[0].metadata.name}') --name 6565 -o json

...
                "name": "places.trip.svc.cluster.local:6565",
                "domains": [
                    "places.trip.svc.cluster.local",
                    "places.trip.svc.cluster.local:6565",
                    "places",
                    "places:6565",
                    "places.trip.svc.cluster",
                    "places.trip.svc.cluster:6565",
                    "places.trip.svc",
                    "places.trip.svc:6565",
                    "places.trip",
                    "places.trip:6565",
                    "10.250.134.101",
                    "10.250.134.101:6565"
                ],
                "routes": [
                    {
                        "match": {
                            "prefix": "/"
                        },
                        "route": {
                            "cluster": "outbound|6565||places-primary.trip.svc.cluster.local",
...

[stefanprodan]

This looks great! Can you please change the FAQ and remove the but the virtual service will point to the port specified in spec.service.port.

Next step would be to turn on port discovery in the Istio e2e and add --port-metrics=9797 to podinfo. This way the e2e testing will be running with multiple ports and validate your PR.

[stefanprodan]

LGTM

Thanks @fcantournet