Add support for postStart events in DevWorkspaces

[amisevsk]

What does this PR do?

Adds basic support for postStart events in DevWorkspaces by utilizing Kubernetes pod lifecycle hooks. Hooks allow for running commands after a container starts, with the caveats:

• There's no guarantee the container's entrypoint has run
• The command is re-run on every container start (i.e. if a container crashes the hook executes again)
• If the hook returns a non-zero exit code, container startup fails

This PR has some additional limitations:

• Only exec-type commands are supported (perhaps we could also support composite commands if they're all exec...)
• The workingDir field is supported via cd <workingDir> but other fields (e.g. env) are currently not
• Only one postStart event can be tied to each component, we don't join commands

The limitations above can be improved later if necessary.

What issues does this PR fix or reference?

Closes #629
Closes #655

Is it tested? How?

1. Create a DevWorkspace that specifies a postStart event:

   cat <<EOF | kubectl apply -f -
   kind: DevWorkspace
   apiVersion: workspace.devfile.io/v1alpha2
   metadata:
     name: test-poststart
   spec:
     started: true
     template:
       projects:
         - name: web-nodejs-sample
           git:
             remotes:
               origin: "https://github.com/che-samples/web-nodejs-sample.git"
       components:
         - name: theia
           plugin:
             uri: https://che-plugin-registry-main.surge.sh/v3/plugins/eclipse/che-theia/next/devfile.yaml
             components:
               - name: theia-ide
                 container:
                   env:
                     - name: THEIA_HOST
                       value: 0.0.0.0
       commands:
         - id: say-hello
           exec:
             component: theia-ide
             commandLine: echo "Hello from postStart!" > postStart-event.log
             workingDir: ${PROJECTS_ROOT}
       events:
         postStart:
           - say-hello
   EOF

2. Wait for workspace to enter running state
3. Check that postStart-event.log file is created:

   WKSP_ID=$(kubectl get dw test-poststart -o json | jq -r '.status.devworkspaceId')
   kubectl exec deploy/${WKSP_ID} -c theia-ide -- cat '/projects/postStart-event.log'

   should output Hello from postStart!

PR Checklist

• E2E tests pass (when PR is ready, comment /test v8-devworkspace-operator-e2e, v8-che-happy-path to trigger)
  • v8-devworkspace-operator-e2e: DevWorkspace e2e test
  • v8-che-happy-path: Happy path for verification integration with Che

[sleshchenko]

Changes LGTM but it does not seem to work ideally for Che case, or for devfile case in general, but seems to may work in happy path )
Failure and edge cases seems to become more complex to investigate (instead of checking logs, you would need to build your process in a way it reports logs onto filesystem, and you should design your postStart events to start in not-blocking manner. In case it crashed - no one will take care of it and you would need to do exec and analyze processes and their logs on file system)

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: amisevsk, sleshchenko

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[benoitf]

FYI I tried with this DevWorkspace: https://gist.github.com/benoitf/541ffeac548fd33d91f91fbe2232de2d

$ kubectl apply -f https://gist.githubusercontent.com/benoitf/541ffeac548fd33d91f91fbe2232de2d/raw/f8f006a4f8617aedfeb9e6a94e94901ce40472ef/devworkspace-post-start.yaml

when I do oc get dw I've the following output:

NAME               DEVWORKSPACE ID             PHASE      INFO
my-dummy-project   workspace10131a939b7f4b05   Starting   Waiting for editor to start

but trying the route that can be grabbed using

$ oc get dwr -o yaml | grep 'url:'
        url: https://workspace10131a939b7f4b05.apps.cluster-4ad3.4ad3.sandbox1894.opentlc.com/che-code/

I'm able to connect to the IDE

[benoitf]

My DevWorkspace has one init-container which is used as a preStart command: it copy IDE content to a volume
Then postStart event is used to start the IDE from the mounted volume

The ide is running and I'm able to connect on the DevWorkspaceRoute but I still have the state Waiting for editor to start

[amisevsk]

The issue is that the editor is returning 400 Bad Request for the /healthz endpoint, breaking the health check that marks a workspace as running. I can add it to ignored reasons (our health checks are generally pretty fragile currently), but that failure does appear to be unrelated to this PR.

[amisevsk]

Waiting on editor to start error should be fixed by #662

Side note on usability: the editor's URL can always be grabbed via oc get dw -o json | jq '.status.mainUrl', even if the workspace is not running.

[openshift-ci]

New changes are detected. LGTM label has been removed.

[sleshchenko]

/test v8-devworkspace-operator-e2e, v8-che-happy-path

[amisevsk]

Rebased to include #662, which should fix @benoitf's use case.

[amisevsk]

/test v8-devworkspace-operator-e2e, v8-che-happy-path