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docs/debugging/application-debugging-guide.md

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Application Debugging Guide

You deployed your app to Knative Serving, but it isn't working as expected. Go through this step by step guide to understand what failed.

Check command line output

Check your deploy command output to see whether it succeeded or not. If your deployment process was terminated, there should be an error message showing up in the output that describes the reason why the deployment failed.

This kind of failure is most likely due to either a misconfigured manifest or wrong command. For example, the following output says that you must configure route traffic percent to sum to 100:

Error from server (InternalError): error when applying patch:
{"metadata":{"annotations":{"kubectl.kubernetes.io/last-applied-configuration":"{\"apiVersion\":\"serving.knative.dev/v1alpha1\",\"kind\":\"Route\",\"metadata\":{\"annotations\":{},\"name\":\"route-example\",\"namespace\":\"default\"},\"spec\":{\"traffic\":[{\"configurationName\":\"configuration-example\",\"percent\":50}]}}\n"}},"spec":{"traffic":[{"configurationName":"configuration-example","percent":50}]}}
to:
&{0xc421d98240 0xc421e77490 default route-example STDIN 0xc421db0488 264682 false}
for: "STDIN": Internal error occurred: admission webhook "webhook.knative.dev" denied the request: mutation failed: The route must have traffic percent sum equal to 100.
ERROR: Non-zero return code '1' from command: Process exited with status 1

Check application logs

Knative Serving provides default out-of-the-box logs for your application. After entering kubectl proxy, you can go to the Kibana UI to search for logs. (See telemetry guide for more information on logging and monitoring features of Knative Serving.)

Stdout/stderr logs

To find the logs sent to stdout/stderr from your application in the Kibana UI:

  1. Click Discover on the left side bar.
  2. Choose logstash-* index pattern on the left top.
  3. Input tag: kubernetes* in the top search bar then search.

Request logs

To find the request logs of your application in the Kibana UI :

  1. Click Discover on the left side bar.
  2. Choose logstash-* index pattern on the left top.
  3. Input tag: "requestlog.logentry.istio-system" in the top search bar then search.

Check Route status

Run the following command to get the status of the Route object with which you deployed your application:

kubectl get route <route-name> -o yaml

The conditions in status provide the reason if there is any failure. For details, see Knative Error Conditions and Reporting(currently some of them are not implemented yet).

Check Istio routing

Compare your Knative Route object's configuration (obtained in the previous step) to the Istio RouteRule object's configuration.

Enter the following, replacing <routerule-name> with the appropriate value:

kubectl get routerule <routerule-name> -o yaml

If you don't know the name of your route rule, use the kubectl get routerule command to find it.

The command returns the configuration of your route rule. Compare the domains between your route and route rule; they should match.

Check ingress status

Enter:

kubectl get ingress

The command returns the status of the ingress. You can see the name, age, domains, and IP address.

Check Revision status

If you configure your Route with Configuration, run the following command to get the name of the Revision created for you deployment (look up the configuration name in the Route .yaml file):

kubectl get configuration <configuration-name> -o jsonpath="{.status.latestCreatedRevisionName}"

If you configure your Route with Revision directly, look up the revision name in the Route yaml file.

Then run

kubectl get revision <revision-name> -o yaml

A ready Revision should has the following condition in status:

conditions:
  - reason: ServiceReady
    status: "True"
    type: Ready

If you see this condition, check the following to continue debugging:

If you see other conditions, to debug further:

Check Pod status

To get the Pods for all your deployments:

kubectl get pods

This should list all Pods with brief status. For example:

NAME                                                      READY     STATUS             RESTARTS   AGE
configuration-example-00001-deployment-659747ff99-9bvr4   2/2       Running            0          3h
configuration-example-00002-deployment-5f475b7849-gxcht   1/2       CrashLoopBackOff   2          36s

Choose one and use the following command to see detailed information for its status. Some useful fields are conditions and containerStatuses:

kubectl get pod <pod-name> -o yaml

Check Build status

If you are using Build to deploy, run the following command to get the Build for your Revision:

kubectl get build $(kubectl get revision <revision-name> -o jsonpath="{.spec.buildName}") -o yaml

The conditions in status provide the reason if there is any failure. To access build logs, first execute kubectl proxy and then open Kibana UI. Use any of the following filters within Kibana UI to see build logs. (See telemetry guide for more information on logging and monitoring features of Knative Serving.)

  • All build logs: _exists_:"kubernetes.labels.build-name"
  • Build logs for a specific build: kubernetes.labels.build-name:"<BUILD NAME>"
  • Build logs for a specific build and step: kubernetes.labels.build-name:"<BUILD NAME>" AND kubernetes.container_name:"build-step-<BUILD STEP NAME>"