Understand your Mesh with Istioctl Describe

The following information describes an experimental feature, which is intendedfor evaluation purposes only.

In Istio 1.3, we included the istioctl experimental describecommand. This CLI command provides you with the information needed to understandthe configuration impacting a pod. This guide showsyou how to use this experimental sub-command to see if a pod is in the mesh andverify its configuration.

The basic usage of the command is as follows:

  1. $ istioctl experimental describe <pod-name>[.<namespace>]

Appending a namespace to the pod name has the same affect as using the -n optionof istioctl to specify a non-default namespace.

Just like all other istioctl commands, you can replace experimentalwith x for convenience.

This guide assumes you have deployed the Bookinfosample in your mesh. If you haven’t already done so,start the application’s servicesand determine the IP and port of the ingressbefore continuing.

Verify a pod is in the mesh

The istioctl describe command returns a warning if the Envoyproxy is not present in a pod or if the proxy has not started. Additionally, the command warnsif some of the [Istio requirements for pods]/docs/ops/prep/requirements/)are not met.

For example, the following command produces a warning indicating a kubernetes-dashboardpod is not part of the service mesh because it has no sidecar:

  1. $ export DASHBOARD_POD=$(kubectl -n kube-system get pod -l k8s-app=kubernetes-dashboard -o jsonpath='{.items[0].metadata.name}')
  2. $ istioctl x describe pod -n kube-system $DASHBOARD_POD
  3. WARNING: kubernetes-dashboard-7996b848f4-nbns2.kube-system is not part of mesh; no Istio sidecar

The command will not produce such a warning for a pod that is part of the mesh,the Bookinfo ratings service for example, but instead will output the Istio configuration applied to the pod:

  1. $ export RATINGS_POD=$(kubectl get pod -l app=ratings -o jsonpath='{.items[0].metadata.name}')
  2. $ istioctl experimental describe pod $RATINGS_POD
  3. Pod: ratings-v1-f745cf57b-qrxl2
  4. Pod Ports: 9080 (ratings), 15090 (istio-proxy)
  5. --------------------
  6. Service: ratings
  7.    Port: http 9080/HTTP
  8. Pilot reports that pod enforces HTTP/mTLS and clients speak HTTP

The output shows the following information:

  • The ports of the service container in the pod, 9080 for the ratings container in this example.
  • The ports of the istio-proxy container in the pod, 15090 in this example.
  • The protocol used by the service in the pod, HTTP over port 9080 in this example.
  • The mutual TLS settings for the pod.

Verify destination rule configurations

You can use istioctl describe to see whatdestination rules apply to requeststo a pod. For example, apply the Bookinfomutual TLS destination rules:

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  1. $ kubectl apply -f @samples/bookinfo/networking/destination-rule-all-mtls.yaml@

Now describe the ratings pod again:

  1. $ istioctl x describe pod $RATINGS_POD
  2. Pod: ratings-v1-f745cf57b-qrxl2
  3.    Pod Ports: 9080 (ratings), 15090 (istio-proxy)
  4. --------------------
  5. Service: ratings
  6.    Port: http 9080/HTTP
  7. DestinationRule: ratings for "ratings"
  8.    Matching subsets: v1
  9.       (Non-matching subsets v2,v2-mysql,v2-mysql-vm)
  10.    Traffic Policy TLS Mode: ISTIO_MUTUAL
  11. Pilot reports that pod enforces HTTP/mTLS and clients speak mTLS

The command now shows additional output:

  • The ratings destination rule applies to request to the ratings service.
  • The subset of the ratings destination rule that matches the pod, v1 in this example.
  • The other subsets defined by the destination rule.
  • The pod accepts either HTTP or mutual TLS requests but clients use mutual TLS.

Verify virtual service configurations

When virtual services configureroutes to a pod, istioctl describe will also include the routes in its output.For example, apply theBookinfo virtual servicesthat route all requests to v1 pods:

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  1. $ kubectl apply -f @samples/bookinfo/networking/virtual-service-all-v1.yaml@

Then, describe a pod implementing v1 of the reviews service:

  1. $ export REVIEWS_V1_POD=$(kubectl get pod -l app=reviews,version=v1 -o jsonpath='{.items[0].metadata.name}')
  2. $ istioctl x describe pod $REVIEWS_V1_POD
  3. ...
  4. VirtualService: reviews
  5.    1 HTTP route(s)

The output contains similar information to that shown previously for the ratings pod,but it also includes the virtual service’s routes to the pod.

The istioctl describe command doesn’t just show the virtual services impacting the pod.If a virtual service configures the service host of a pod but no traffic will reach it,the command’s output includes a warning. This case can occur if the virtual serviceactually blocks traffic by never routing traffic to the pod’s subset. Forexample:

  1. $ export REVIEWS_V2_POD=$(kubectl get pod -l app=reviews,version=v2 -o jsonpath='{.items[0].metadata.name}')
  2. $ istioctl x describe pod $REVIEWS_V2_POD
  3. ...
  4. VirtualService: reviews
  5.    WARNING: No destinations match pod subsets (checked 1 HTTP routes)
  6.       Route to non-matching subset v1 for (everything)

The warning includes the cause of the problem, how many routes were checked, andeven gives you information about the other routes in place. In this example,no traffic arrives at the v2 pod because the route in the virtual service directs alltraffic to the v1 subset.

If you now delete the Bookinfo destination rules:

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  1. $ kubectl delete -f @samples/bookinfo/networking/destination-rule-all-mtls.yaml@

You can see another useful feature of istioctl describe:

  1. $ istioctl x describe pod $REVIEWS_V1_POD
  2. ...
  3. VirtualService: reviews
  4.    WARNING: No destinations match pod subsets (checked 1 HTTP routes)
  5.       Warning: Route to subset v1 but NO DESTINATION RULE defining subsets!

The output shows you that you deleted the destination rule but not the virtualservice that depends on it. The virtual service routes traffic to the v1subset, but there is no destination rule defining the v1 subset.Thus, traffic destined for version v1 can’t flow to the pod.

If you refresh the browser to send a new request to Bookinfo at thispoint, you would see the following message: Error fetching product reviews.To fix the problem, reapply the destination rule:

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  1. $ kubectl apply -f @samples/bookinfo/networking/destination-rule-all-mtls.yaml@

Reloading the browser shows the app working again andrunning istioctl experimental describe pod $REVIEWS_V1_POD no longer produceswarnings.

Verifying traffic routes

The istioctl describe command shows split traffic weights too.For example, run the following command to route 90% of traffic to the v1 subsetand 10% to the v2 subset of the the reviews service:

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  1. $ kubectl apply -f @samples/bookinfo/networking/virtual-service-reviews-90-10.yaml@

Now describe the reviews v1 pod:

  1. $ istioctl x describe pod $REVIEWS_V1_POD
  2. ...
  3. VirtualService: reviews
  4.    Weight 90%

The output shows that the reviews virtual service has a weight of 90% for thev1 subset.

This function is also helpful for other types of routing. For example, you can deployheader-specific routing:

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  1. $ kubectl apply -f @samples/bookinfo/networking/virtual-service-reviews-jason-v2-v3.yaml@

Then, describe the pod again:

  1. $ istioctl x describe pod $REVIEWS_V1_POD
  2. ...
  3. VirtualService: reviews
  4.    WARNING: No destinations match pod subsets (checked 2 HTTP routes)
  5.       Route to non-matching subset v2 for (when headers are end-user=jason)
  6.       Route to non-matching subset v3 for (everything)

The output produces a warning since you are describing a pod in the v1 subset.However, the virtual service configuration you applied routes traffic to the v2subset if the header contains end-user=jason and to the v3 subset in allother cases.

Verifying strict mutual TLS

Following the mutual TLS migrationinstructions, you can enable strict mutual TLS for the ratings service:

  1. $ kubectl apply -f - <<EOF
  2. apiVersion: "authentication.istio.io/v1alpha1"
  3. kind: "Policy"
  4. metadata:
  5.   name: "ratings-strict"
  6. spec:
  7.   targets:
  8.   - name: ratings
  9.   peers:
  10.   - mtls:
  11.       mode: STRICT
  12. EOF

Run the following command to describe the ratings pod:

  1. $ istioctl x describe pod $RATINGS_POD
  2. Pilot reports that pod enforces mTLS and clients speak mTLS

The output reports that requests to the the ratings pod are now locked down and secure.

Sometimes, however, a deployment breaks when switching mutual TLS to STRICT.The likely cause is that the destination rule didn’t match the new configuration.For example, if you configure the Bookinfo clients to not use mutual TLS using theplain HTTP destination rules:

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  1. $ kubectl apply -f @samples/bookinfo/networking/destination-rule-all.yaml@

If you open Bookinfo in your browser, you see Ratings service is currently unavailable.To learn why, run the following command:

  1. $ istioctl x describe pod $RATINGS_POD
  2. ...
  3. WARNING Pilot predicts TLS Conflict on ratings-v1-f745cf57b-qrxl2 port 9080 (pod enforces mTLS, clients speak HTTP)
  4.   Check DestinationRule ratings/default and AuthenticationPolicy ratings-strict/default

The output includes a warning describing the conflictbetween the destination rule and the authentication policy.

You can restore correct behavior by applying a destination rule that usesmutual TLS:

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  1. $ kubectl apply -f @samples/bookinfo/networking/destination-rule-all-mtls.yaml@

Conclusion and cleanup

Our goal with the istioctl x describe command is to help you understand thetraffic and security configurations in your Istio mesh.

We would love to hear your ideas for improvements!Please join us at https://discuss.istio.io.

To remove the Bookinfo pods and configurations used in this guide, run thefollowing commands:

ZipZipZipZip

  1. $ kubectl delete -f @samples/bookinfo/platform/kube/bookinfo.yaml@
  2. $ kubectl delete -f @samples/bookinfo/networking/bookinfo-gateway.yaml@
  3. $ kubectl delete -f @samples/bookinfo/networking/destination-rule-all-mtls.yaml@
  4. $ kubectl delete -f @samples/bookinfo/networking/virtual-service-all-v1.yaml@

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