Added signal handling in SidecarLog results to support Kubernetes-native sidecar functionality

[pritidesai]

Changes

In the native Kubernetes sidecar model, sidecars are implemented as init containers with a RestartPolicy: Always, which means they run for the entire duration of the pod's lifecycle. However, the current Tekton sidecar log results implementation doesn't account for this behavior and exits after processing results, causing the container to restart repeatedly.

This PR enhances the sidecarlogresults binary to support Kubernetes native sidecars by:

• Adding a new -kubernetes-sidecar-mode flag that, when enabled, prevents the sidecar from exiting after processing results
• Implementing proper signal handling to ensure a graceful shutdown when the pod is terminated

A sample pipelineRun with DinD and task results:

Before:

kubectl get pod large-result-pipeline-run6pvd8-large-task-pod -o json | jq '.status.initContainerStatuses[] | {name: .name, exitCode: .state.terminated.exitCode, restartCount: .restartCount}'  

{
  "name": "prepare",
  "exitCode": 0,
  "restartCount": 0
}
{
  "name": "place-scripts",
  "exitCode": 0,
  "restartCount": 0
}
{
  "name": "sidecar-server",
  "exitCode": 0,
  "restartCount": 0
}
{
  "name": "sidecar-tekton-log-results",
  "exitCode": 0,
  "restartCount": 8
}

After:

kubectl get pod large-result-pipeline-rundnpvb-large-task-pod -o json | jq '.status.initContainerStatuses[] | {name: .name, exitCode: .state.terminated.exitCode, restartCount: .restartCount}'  

{
  "name": "prepare",
  "exitCode": 0,
  "restartCount": 0
}
{
  "name": "place-scripts",
  "exitCode": 0,
  "restartCount": 0
}
{
  "name": "sidecar-server",
  "exitCode": 0,
  "restartCount": 0
}
{
  "name": "sidecar-tekton-log-results",
  "exitCode": 0,
  "restartCount": 0
}

/kind bug

Submitter Checklist

As the author of this PR, please check off the items in this checklist:

• Has Docs if any changes are user facing, including updates to minimum requirements e.g. Kubernetes version bumps
• Has Tests included if any functionality added or changed
• pre-commit Passed
• Follows the commit message standard
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• Release notes contains the string "action required" if the change requires additional action from users switching to the new release

Release Notes

Added signal handling to SidecarLog to support Kubernetes-native sidecar functionality, preventing repeated restarts of the init container.

[tekton-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: vdemeester

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[pritidesai]

Thank you @vdemeester for approving this PR.

@afrittoli, @waveywaves, @twoGiants - I would appreciate it if you could review this PR as well.

I would like to have this PR included in the 1.6 release.

[vdemeester]

/lgtm