Workflow and Template status change notification/trigger using Lifecycle Hook

[sarabala1979]

Summary

Inspiration from #4355. We can add workflow and template lifecycle hook

Example:
Lifecycle hook (Workflow level and Template level)
Option 1:

  hooks:
    running:
      template: notify
      arguments:
        parameters:
          - name: status
            value: "{{workflows.status}}"
    failed:
      template: notify-failed
      arguments:
        parameters:
          - name: status
            value: "{{workflows.status}}"
    succeed:
      template: notify-success
      arguments:
        parameters:
          - name: status
            value: "{{workflows.status}}"
    errored:
      template: notify-errord
      arguments:
        parameters:
          - name: status
            value: "{{workflows.status}}"

Option2:

  hooks:
   statusUpdate:
      template: notify
      arguments:
        parameters:
          - name: status
            value: "{{workflows.status}}"

[alexec]

Just a thought: make consistent with pod hooks:

https://kubernetes.io/docs/tasks/configure-pod-container/attach-handler-lifecycle-event/

[sarabala1979]

Sample workflow

apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
  generateName: lifecycle-hook-
spec:
  entrypoint: diamond
  hooks:
    running:
      expression: "{{workflow.status}} == Running"
      template: http
  templates:
    - name: diamond
      dag:
        tasks:
          - name: A
            hooks:
              exit:
                template: http
              success:
                expression: "{{tasks.A.status}} == Succeeded"
                template: http
              failure:
                expression: "{{tasks.A.status}} == Failed"
                template: http
              error:
                expression: "{{tasks.A.status}} == Error"
                template: http
            template: coinflip
          - name: B
            hooks:
              success:
                expression: "{{tasks.B.status}} == Succeeded"
                template: http
            depends: "A"
            template: coinflip
          - name: C
            hooks:
              success:
                expression: "{{tasks.C.status}} == Succeeded"
                template: heads
            depends: "A"
            template: coinflip
          - name: D
            hooks:
              success:
                expression: "{{tasks.D.status}} == Succeeded"
                template: heads
            depends: "B && C"
            template: coinflip
    
    - name: coinflip
      steps:
        #    - - name: flip-coin-1
        #        template: prestart
        - - name: flip-coin
            hooks:
              success:
                expression: "{{steps.flip-coin.status}} == Succeeded"
                template: http
              condition:
                expression: "{{steps.flip-coin.status}} == Succeeded"
                template: http
            template: flip-coin
        - - name: heads
            hooks:
              success:
                expression: "{{steps.flip-coin.outputs.result}} == heads"
                template: heads
            template: http
            when: "{{steps.flip-coin.outputs.result}} == heads"
          - name: tails
      
            template: heads
            when: "{{steps.flip-coin.outputs.result}} == tails"
    
    - name: flip-coin
      script:
        image: python:alpine3.6
        command: [python]
        source: |
          import random
          result = "heads" if random.randint(0,1) == 0 else "tails"
          print(result)
    
    - name: heads
      container:
        image: alpine:3.6
        command: [sh, -c]
        args: ["echo \"it was heads\""]

    - name: http
      http:
        # url: http://dummy.restapiexample.com/api/v1/employees
        url: "https://raw.githubusercontent.com/argoproj/argo-workflows/4e450e250168e6b4d51a126b784e90b11a0162bc/pkg/apis/workflow/v1alpha1/generated.swagger.json"

[alexec]

Fixed I think?