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docs/debugging/application-debugging-guide.md

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Application Debugging Guide

You deployed your app to Elafros but it is not 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 error message showing up in the output and describing the reason why the deployment failed.

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

Error from server (InternalError): error when applying patch:
{"metadata":{"annotations":{"kubectl.kubernetes.io/last-applied-configuration":"{\"apiVersion\":\"elafros.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.elafros.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 Route status

Run the following command to get status of the Route 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 Elafro Error Conditions and Reporting(currently some of them are not implemented yet).

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

kebuctl 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, to debug further:

  1. Check Pod status
  2. Check application logs
  3. Check Istio routing

If you see other conditions, to debug further:

  1. Look up the meaning of the conditions in Elafro Error Conditions and Reporting. Note: some of them are not implemented yet. An alternation is to check Pod status.
  2. If you are using BUILD to deploy and the BuidComplete condition is not True, check BUILD status.

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.

Check application logs

Elafros provides default out-of-box logs for your application. After executing kubectl proxy, you can go to the Kibana UI to search for logs. You need to do create an index when you open Kibana for the first time. See this instruction for details.

Stdout/stderr logs

You can find the logs emitted to stdout/stderr from your application on Kibana UI by following steps:

  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

You can find the request logs of your application on Kibana UI by following steps:

  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 Istio routing

TBD.