callback-basic

Basic callback endpoint sample

In this sample, you will see to create a callback endpoint within your workflow that can receive HTTP GET or POST requests and in a later step wait for a request to arrive at that endpoint.

Enable services

First, enable required services:

gcloud services enable workflows.googleapis.com

Define workflow

Create a workflow-get.yaml and [worklow-post.yaml](workflow-post.yaml] to define workflows accepting HTTP GET or POST.

In the create_callback step, create an endpoint with GET:

- create_callback:
    call: events.create_callback_endpoint
    args:
        http_callback_method: "GET"
    result: callback_details

Or you could create an endpoint with POST:

- create_callback:
    call: events.create_callback_endpoint
    args:
        http_callback_method: "POST"
    result: callback_details

In the second step, print the url for the callback endpoint:

- print_callback_details:
    call: sys.log
    args:
        severity: "INFO"
        text: ${"Listening for callbacks on " + callback_details.url}

In the third step, wait for the callback to be called with a timeout:

- await_callback:
    call: events.await_callback
    args:
        callback: ${callback_details}
        timeout: 3600
    result: callback_request

In the last step, print the callback result:

- print_callback_result:
    return: ${callback_request.http_request}

Deploy and execute workflow

Deploy workflows:

gcloud workflows deploy callback-basic-get --source=workflow-get.yaml
gcloud workflows deploy callback-basic-post --source=workflow-post.yaml

Run workflows:

gcloud workflows run callback-basic-get
gcloud workflows run callback-basic-post

The workflow should be in waiting state right now. Check the logs to find the url of the callback.

Test

Assuming that you have Workflows Editor or Workflows Admin roles, you can call the workflow with gcloud.

To test the workflow waiting for GET:

CALLBACK_URL=https://workflowexecutions.googleapis.com/v1/projects/...
curl -X GET -H "Authorization: Bearer $(gcloud auth print-access-token)" $CALLBACK_URL

To test the workflow waiting for POST:

CALLBACK_URL=https://workflowexecutions.googleapis.com/v1/projects/...
curl -X POST -H "Content-Type: application/json" -H "Authorization: Bearer $(gcloud auth print-access-token)" -d '{"foo" : "bar"}' $CALLBACK_URL

You should see the workflow execution succeed.