Lifecycle-Hook¶

v3.3 and after

Introduction¶

A LifecycleHook triggers an action based on a conditional expression or on completion of a step or template. It is configured either at the workflow-level or template-level, for instance as a function of the workflow.status or steps.status, respectively. A LifecycleHook executes during execution time and executes once. It will execute in parallel to its step or template once the expression is satisfied.

In other words, a LifecycleHook functions like an exit handler with a conditional expression. You must not name a LifecycleHook exit or it becomes an exit handler; otherwise the hook name has no relevance.

Workflow-level LifecycleHook: Executes the template when a configured expression is met during the workflow.

Workflow-level Lifecycle-Hook example

Template-level Lifecycle-Hook: Executes the template when a configured expression is met during the step in which it is defined.

Template-level Lifecycle-Hook example

Supported conditions¶

Exit handler variables: workflow.status and workflow.failures
template
templateRef
arguments

Unsupported conditions¶

outputs are not usable since LifecycleHook executes during execution time and outputs are not produced until the step is completed. You can use outputs from previous steps, just not the one you're hooking into. If you'd like to use outputs create an exit handler instead - all the status variable are available there so you can still conditionally decide what to do.

Notification use case¶

A LifecycleHook can be used to configure a notification depending on a workflow status change or template status change, like the example below:

apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
 generateName: lifecycle-hook-
spec:
 entrypoint: main
 hooks:
   exit:
     template: http
   running:
     expression: workflow.status == "Running"
     template: http
 templates:
   - name: main
     steps:
       - - name: step1
           template: heads

   - 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

Put differently, an exit handler is like a workflow-level LifecycleHook with an expression of workflow.status == "Succeeded" or workflow.status == "Failed" or workflow.status == "Error".

Have a question?

Search on GitHub Discussions and Slack.