Doc: How to read log of the steps

[cmoulliard]

Doc feature - How to read log of the steps

When a taskRun or pipelineRun is executed with several steps, then a container is created for the step defined and the log content could be accessed to check what happened.
the doc should explain how to find the containers - steps and how to read the log

Example

kc get taskruns/build-docker-image-from-git-source-task-run -o yaml -n tutorial
apiVersion: tekton.dev/v1alpha1
kind: TaskRun
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"tekton.dev/v1alpha1","kind":"TaskRun","metadata":{"annotations":{},"name":"build-docker-image-from-git-source-task-run","namespace":"tutorial"},"spec":{"inputs":{"params":[{"name":"pathToDockerFile","value":"Dockerfile"},{"name":"pathToContext","value":"/workspace/docker-source/examples/microservices/leeroy-web"}],"resources":[{"name":"docker-source","resourceRef":{"name":"skaffold-git"}}]},"outputs":{"resources":[{"name":"builtImage","resourceRef":{"name":"skaffold-image-leeroy-web"}}]},"taskRef":{"name":"build-docker-image-from-git-source"}}}
  creationTimestamp: "2019-05-23T06:03:56Z"
  generation: 1
  labels:
    tekton.dev/task: build-docker-image-from-git-source
  name: build-docker-image-from-git-source-task-run
  namespace: tutorial
  resourceVersion: "91117"
  selfLink: /apis/tekton.dev/v1alpha1/namespaces/tutorial/taskruns/build-docker-image-from-git-source-task-run
  uid: 8cbe8cb2-7d20-11e9-927b-fa163eaa1b05
spec:
  inputs:
    params:
    - name: pathToDockerFile
      value: Dockerfile
    - name: pathToContext
      value: /workspace/docker-source/examples/microservices/leeroy-web
    resources:
    - name: docker-source
      resourceRef:
        name: skaffold-git
  outputs:
    resources:
    - name: builtImage
      resourceRef:
        name: skaffold-image-leeroy-web
  taskRef:
    kind: Task
    name: build-docker-image-from-git-source
  trigger:
    type: ""
status:
  completionTime: "2019-05-23T06:04:23Z"
  conditions:
  - lastTransitionTime: "2019-05-23T06:04:23Z"
    message: '"build-step-build-and-push" exited with code 1 (image: "docker-pullable://gcr.io/kaniko-project/executor@sha256:d9fe474f80b73808dc12b54f45f5fc90f7856d9fc699d4a5e79d968a1aef1a72");
      for logs run: kubectl -n tutorial logs build-docker-image-from-git-source-task-run-pod-e31c31
      -c build-step-build-and-push'
...

Next, check the log of the pod

kubectl -n tutorial logs build-docker-image-from-git-source-task-run-pod-e31c31
Error from server (BadRequest): a container name must be specified for pod build-docker-image-from-git-source-task-run-pod-e31c31, choose one of: [build-step-git-source-skaffold-git-r7hj8 build-step-build-and-push nop] or one of the init containers: [build-step-credential-initializer-stpr4 build-step-place-tools]

Get container's log

kubectl -n tutorial logs build-docker-image-from-git-source-task-run-pod-e31c31 -c build-step-build-and-push               
INFO[0000] Downloading base image golang:1.10.1-alpine3.7 
2019/05/23 06:04:01 No matching credentials were found, falling back on anonymous
INFO[0000] Executing 0 build triggers                   
INFO[0000] Unpacking rootfs as cmd RUN go build -o /web . requires it. 
INFO[0006] Taking snapshot of full filesystem...        
INFO[0007] Skipping paths under /kaniko, as it is a whitelisted directory 
INFO[0007] Skipping paths under /builder/tools, as it is a whitelisted directory 
...

[vdemeester]

There is several possibilities to do that, but please keep in mind this is still early.

• a taskrun creating a pod, you need to read the pod log as you described. You can use ˋ—all-containers` flag on kubectl to see the logs from all the containers
• tektoncd/cli aims to answer those questions/features, by providing a cli focused on pipeline (and thus not on kubectl constructs)
• tektoncd/dashboard has the same aim but from a web interface instead of a command line

[skaegi]

@vdemeester I sometimes wonder if we should just bite the bullet and do api aggregation to have a common logs endpoint on TaskRuns. e.g. so we could support kubectl logs on TaskRun names.

I was looking at kubernetes/kubernetes#72637 -- and a generic logs sub-resource we can use via CRD does not seem to be imminent.

[vdemeester]

@skaegi yes we may have to go that route at some point 😅

[bobcatfish]

We should definitely document one or more of the current solutions!