K
Q

istio routing between two pods

8/30/2018

trying to get into istio on kubernetes but it seems i am missing either some fundamentals, or i am doing things back to front. I am quite experienced in kubernetes, but istio and its virtualservice confuses me a bit.

I created 2 deployments (helloworld-v1/helloworld-v2). Both have the same image, the only thing thats different is the environment variables - which output either version: "v1" or version: "v2". I am using a little testcontainer i wrote which basically returns the headers i got into the application. A kubernetes service named "helloworld" can reach both.

I created a Virtualservice and a Destinationrule

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: helloworld
spec:
  hosts:
  - helloworld
http:
  - route:
     - destination:
       host: helloworld
       subset: v1
     weight: 90
     - destination:
       host: helloworld
       subset: v2
     weight: 10
---
apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: helloworld
spec:
  host: helloworld
  subsets:
  - name: v1
    labels:
      version: v1
  - name: v2
    labels:
      version: v2

According to the docs not mentioning any gateway should use the internal "mesh" one. Sidecar containers are successfully attached:

kubectl -n demo get all
NAME                                 READY     STATUS    RESTARTS   AGE
pod/curl-6657486bc6-w9x7d            2/2       Running   0          3h
pod/helloworld-v1-d4dbb89bd-mjw64    2/2       Running   0          6h
pod/helloworld-v2-6c86dfd5b6-ggkfk   2/2       Running   0          6h

NAME                 TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)    AGE
service/helloworld   ClusterIP   10.43.184.153   <none>        80/TCP     6h

NAME                            DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/curl            1         1         1            1           3h
deployment.apps/helloworld-v1   1         1         1            1           6h
deployment.apps/helloworld-v2   1         1         1            1           6h

NAME                                       DESIRED   CURRENT   READY     AGE
replicaset.apps/curl-6657486bc6            1         1         1         3h
replicaset.apps/helloworld-v1-d4dbb89bd    1         1         1         6h
replicaset.apps/helloworld-v2-6c86dfd5b6   1         1         1         6h

Everything works quite fine when i access the application from "outside" (istio-ingressgateway), v2 is called one times, v1 9 nine times:

curl --silent -H 'host: helloworld' http://localhost
{"host":"helloworld","user-agent":"curl/7.47.0","accept":"*/*","x-forwarded-for":"10.42.0.0","x-forwarded-proto":"http","x-envoy-internal":"true","x-request-id":"a6a2d903-360f-91a0-b96e-6458d9b00c28","x-envoy-decorator-operation":"helloworld:80/*","x-b3-traceid":"e36ef1ba2229177e","x-b3-spanid":"e36ef1ba2229177e","x-b3-sampled":"1","x-istio-attributes":"Cj0KF2Rlc3RpbmF0aW9uLnNlcnZpY2UudWlkEiISIGlzdGlvOi8vZGVtby9zZXJ2aWNlcy9oZWxsb3dvcmxkCj8KGGRlc3RpbmF0aW9uLnNlcnZpY2UuaG9zdBIjEiFoZWxsb3dvcmxkLmRlbW8uc3ZjLmNsdXN0ZXIubG9jYWwKJwodZGVzdGluYXRpb24uc2VydmljZS5uYW1lc3BhY2USBhIEZGVtbwooChhkZXN0aW5hdGlvbi5zZXJ2aWNlLm5hbWUSDBIKaGVsbG93b3JsZAo6ChNkZXN0aW5hdGlvbi5zZXJ2aWNlEiMSIWhlbGxvd29ybGQuZGVtby5zdmMuY2x1c3Rlci5sb2NhbApPCgpzb3VyY2UudWlkEkESP2t1YmVybmV0ZXM6Ly9pc3Rpby1pbmdyZXNzZ2F0ZXdheS01Y2NiODc3NmRjLXRyeDhsLmlzdGlvLXN5c3RlbQ==","content-length":"0","version":"v1"}
"version": "v1",
"version": "v1",
"version": "v2",
"version": "v1",
"version": "v1",
"version": "v1",
"version": "v1",
"version": "v1",
"version": "v1",

But as soon as i do the curl from within a pod (in this case just byrnedo/alpine-curl) against the service things start to get confusing:

curl --silent -H 'host: helloworld' http://helloworld.demo.svc.cluster.local
{"host":"helloworld","user-agent":"curl/7.61.0","accept":"*/*","version":"v1"}
"version":"v2"
"version":"v2"
"version":"v1"
"version":"v1"
"version":"v2"
"version":"v2"
"version":"v1"
"version":"v2“
"version":"v1"

Not only that i miss all the istio attributes (which i understand in a service to service communication because as i understand it they are set when the request first enters the mesh via gateway), but the balance for me looks like the default 50:50 balance of a kubernetes service.

What do i have to do to achieve the same 1:9 balance on an inter-service communication? Do i have to create a second, "internal" gateway to use instead the service fqdn? Did i miss a definition? Should calling a service fqdn from within a pod respect a virtualservice routing?

used istio version is 1.0.1, used kubernetes version v1.11.1.

UPDATE deployed the sleep-pod as suggested, (this time not relying on the auto-injection of the demo namespace) but manually as described in the sleep sample

kubectl -n demo get deployment sleep -o wide
NAME      DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE       CONTAINERS          IMAGES                                     SELECTOR
sleep     1         1         1            1           2m        
sleep,istio-proxy   tutum/curl,docker.io/istio/proxyv2:1.0.1   app=sleep

Also changed the Virtualservice to 0/100 to see if it works at first glance . Unfortunately this did not change much:

export SLEEP_POD=$(kubectl get -n demo pod -l app=sleep -o jsonpath={.items..metadata.name})
kubectl -n demo exec -it $SLEEP_POD -c sleep curl http://helloworld
{"user- agent":"curl/7.35.0","host":"helloworld","accept":"*/*","version":"v2"}
kubectl -n demo exec -it $SLEEP_POD -c sleep curl http://helloworld
{"user-agent":"curl/7.35.0","host":"helloworld","accept":"*/*","version":"v1"}
kubectl -n demo exec -it $SLEEP_POD -c sleep curl http://helloworld
{"user-agent":"curl/7.35.0","host":"helloworld","accept":"*/*","version":"v2"}
kubectl -n demo exec -it $SLEEP_POD -c sleep curl http://helloworld
{"user-agent":"curl/7.35.0","host":"helloworld","accept":"*/*","version":"v1"}
kubectl -n demo exec -it $SLEEP_POD -c sleep curl http://helloworld
{"user-agent":"curl/7.35.0","host":"helloworld","accept":"*/*","version":"v2"
-- sapien99
istio
kubernetes

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2 Answers

8/30/2018

Routing rules are evaluated on the client side, so you need to make sure that the pod you are running curl from has an Istio sidecar attached to it. If it just calls the service directly, it can't evaluate the 90-10 rule that you set, but instead will just fall through to default kube round-robin routing.

The Istio sleep sample is a good one to use as a test client pod.

-- Frank B
Source: StackOverflow
9/5/2018

Found the solution, one of the prerequisites (i forgot) is that a proper routing requires named ports: @see https://istio.io/docs/setup/kubernetes/spec-requirements/.

Wrong:

spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 3000

Right:

spec:
  ports:
  - name: http
    port: 80
    protocol: TCP
    targetPort: 3000

After using name http everything works like a charm

-- sapien99
Source: StackOverflow