TEP-0069: Support retries for custom task in a pipeline.

[ScrapCodes]

Changes

1. Add field Retries to RunSpec, an integer count which acts as a FYI to
   custom task controller.
2. Add a new RunRetry, in addition to RunCancelled status to RunSpecStatus
   i.e. v1alpha1.RunSpecStatusRetry
3. Add a field RetriesStatus to RunStatusFields, to maintain the retry
   history for a Run, similar to v1beta1.TaskRunStatusFields.RetriesStatus
4. Add a config map entry (default-short-timeout-seconds) to config-defaults in
   order to make short timeout configurable.

Proposed algorithm for performing a retry for custom task.

• Step 1. A pipelineTask consisting of a custom task X, is configured with
  retries count.

• Step 2. On failure of task X, pipelinerun controller sees a request for a
  retry. It then communicates the same to custom task Run by patching
  /spec/status with a v1alpha1.RunSpecStatusRetry i.e. RunRetry. Similar
  to request a custom task to cancel.

• Step 3. In addition to patching the pipelinerun controller also enqueue a timer
  time.After(default-short-timeout-seconds) (default: 30 seconds).
  On completion of timeout (i.e. 30s), it checks if /spec/status is RunRetry,
  then it assumes that custom task does not support retry.

  • a) if custom task does not supports retry as above, It sets no. of retry done
    to the retries count configured - i.e. exhaust all retries.
  • b) if custom task does support retry, update retry history.

• Step 4. The custom task that wants to support the retry, has to update

  • a) status.conditions to indicate it is Running.
  • b) clear /spec/status if it is RunRetry.

A task may retry and immediately fail, so controller cannot fully rely on
status.conditions.

Docs changes

1. Removed the limitation that retries are not supported for custom task.
2. Add a short user guide for custom task developer.

/kind feature

Submitter Checklist

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

• Docs included if any changes are user facing
• Tests included if any functionality added or changed
• Follows the commit message standard
• Meets the Tekton contributor standards (including
  functionality, content, code)
• Release notes block below has been filled in or deleted (only if no user facing changes)

Release Notes

Custom task can be configured with retry. e.g.

            spec:
              pipelineSpec:
                tasks:
                  - name: task-loop-with-retry
                    retries: 2 # retries parameter of a PipelineTask in Pipeline definition.
                    runAfter:
                      - first-task
                    params:
                      - name: word
                        value:
                          - jump
                          - land
                          - roll
                      - name: suffix
                        value: ing
                    taskRef:
                      apiVersion: custom.tekton.dev/v1alpha1
                      kind: TaskLoop
                      name: simpletaskloop

[tekton-robot]

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[tekton-robot]

The following is the coverage report on the affected files.
Say /test pull-tekton-pipeline-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/apis/config/default.go	82.8%	73.5%	-9.2
pkg/apis/pipeline/v1alpha1/run_types.go	43.8%	47.1%	3.3
pkg/apis/pipeline/v1beta1/pipeline_types.go	95.9%	95.8%	-0.1
pkg/reconciler/pipelinerun/pipelinerun.go	83.4%	83.8%	0.4
pkg/reconciler/pipelinerun/resources/pipelinerunresolution.go	92.2%	92.3%	0.1
pkg/reconciler/pipelinerun/resources/pipelinerunstate.go	73.4%	73.5%	0.0

[ScrapCodes]

Currently, I am using time.AfterFunc in this PR. Which is not so ideal performance wise, once the PR #4131 is merged, I will be able to switch to NewRequeueKey .

[tekton-robot]

@ScrapCodes: PR needs rebase.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[afrittoli]

Thanks @ScrapCodes - I look forward to the new PR then!

[ScrapCodes]

Yeah @afrittoli, I have proposed a new approach see tektoncd/community#491