Prometheus gate

[iancoffey]

Changes

This adds a new Task prometheus-gate, aimed at for keeping Tasks and Pipelines gated (eg intentionally blocked) until a certain criteria is met. This Task uses Prometheus range query to obtain range data for the provided query, and asserts all values returned by prometheus are at/above/below target for N times, or fails the pipeline task. The source for the simple gate is here.

Is this a good fit for the catalog? I intend to follow with creating a custom task from this once I have learned more. More details in the linked issue.

Submitter Checklist

These are the criteria that every PR should meet, please check them off as you
review them:

• Includes docs (if user facing)
• Commit messages follow commit message best practices
• Yaml file complies with yamllint rules.
• Complies with Catalog Orgainization TEP, see example. Note An issue has been filed to automate this validation

  • File path follows <kind>/<name>/<version>/name.yaml

  • Has README.md at <kind>/<name>/<version>/README.md

  • Has mandatory metadata.labels - app.kubernetes.io/version the same as the <version> of the resource

  • Has mandatory metadata.annotations tekton.dev/pipelines.minVersion

  • mandatory spec.description follows the convention

      ```
    
      spec:
        description: >-
          one line summary of the resource
    
          Paragraph(s) to describe the resource.
      ```
    

See the contribution guide
for more details.

---

[vinamra28]

• It would be nice if you could add the task with all the files in the task directory

  ./task/         👈 the kind of the resource 
      /prometheus-gate       👈 definition file must have same name
        /0.1
          /README.md     👈 [optional] since there can be a fallback
          /prometheus-gate.yaml   👈 the file name must be resource name
          /samples
           /gate.yaml
           /nginx.yaml

Please see : #389

[iancoffey]

This could use another review, thanks!

[vinamra28]

Can we also have something in the README or in samples as how to use this task 🙂

[iancoffey]

@vinamra28 I added a better samples section and readme 👍

[chmouel]

The CI error seems legit and due of some yaml linting issue..

[iancoffey]

@vinamra28 thanks, CI is passing now :)

[vinamra28]

just last one suggestion could you please squash all your commits 😅 otherwise
/lgtm

[chmouel]

Looking good but the squashing please thanks

[vinamra28]

thank you for the PR 👍
/lgtm

[iancoffey]

Re-squashed and ready for re-review

[vinamra28]

/lgtm

[vdemeester]

/meow

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