Azure Logic Apps: Using HTTP Webhooks

In this post, let's see how we can use a HTTP Webhook in an Azure Logic App to wait for an external event. Note: I am using Azure Logic App Standard model for the purpose of this post.

Imagine we have the following requirement.

• There's a parent workflow and it publishes a Webhook, where consumers can call
• Once the Webhook gets called by a consumer, the parent workflow needs to resume its execution
• There is a consumer, once the consumer received the Webhook information, they can invoke the Webhook at their own decretion,

Let's start by creating the consumer side of things first. Here, in this case, the consumer is another workflow that has a Trigger of type "Request".

Consumer Workflow: When a HTTP request is received

So here my Consumer Workflow accepts a payload that contains the above JSON Schema. The webhookUrl property expects the URL that this consumer will call. Then I have some dummy Delay and then finally I have a HTTP action to make the call to the Webhook.

Consumer Workflow: HTTP Action to call the Webhook

Code

{
  "inputs": {
    "method": "POST",
    "uri": "@{triggerBody()?['webhookUrl']}",
    "body": {
      "messageFromWebhookConsumer": "Name formatting is completed",
      "fullName": "@concat(triggerBody()?['reqObject']?['firstName'], ' ', triggerBody()?['reqObject']?['lastName'])"
    }
  }
}

Here when the Consumer calls the Webhook, I am doing some data transformation and sending that as the payload for the Webhook.

Now we are all good with the consumer workflow.

Next, let's create the parent workflow.

Parent Workflow: When a HTTP request is received

Here in the Parent Workflow, I again have an HTTP trigger. It accepts a payload of the above schema. And the idea is, that we pass this data to the Webhook Consumer, and wait for our Webhook to be called after doing its job.

Now let's add the HTTP Webhook action.

Parent Workflow: HTTP Webhook

Code

{
  "inputs": {
    "subscribe": {
      "method": "POST",
      "uri": "https://logic-ju-test-001.azurewebsites.net:443/api/Webhook-Consumer/triggers/manual/invoke?api-version=2022-05-01&sp=%2Ftriggers%2Fmanual%2Frun&sv=1.0&sig=4rklm9-OkOiRHtj2A_cbW-Lifq6jd",
      "body": {
        "reqObject": "@triggerBody()",
        "webhookUrl": "@listCallbackUrl()"
      }
    },
    "unsubscribe": {}
  }
}

Here for the Subscribe - URI, I have specified the URI for the Consumer Workflow Trigger, and I am passing through the request object that was received for the current workflow along with the Webhook URL (callbackUrl), so the Consumer knows what to call. 

To make things simpler, I am not using any Unsubscribe settings.

Now finally I am introducing a dummy variable assignment to capture the request received to the Webhook.

Parent Workflow: Initialize variable

Code

{
  "inputs": {
    "variables": [
      {
        "name": "reqReceivedToWebhook",
        "type": "object",
        "value": "@body('HTTP_Webhook')"
      }
    ]
  }
}

And that's all about it. 

Now we can call the Parent Workflow via an HTTP Request and see how things are integrating together.

Parent Workflow: Run with payload

Now I can see the Parent Workflow is running for some time. Because it has to call the Consumer and wait for it to call the exposed Webhook.

Parent Workflow: Running

And when the Webhook is called, Parent workflow will complete the execution.

Parent Workflow: Succeeded

And now when we checked the Parent workflow run, we can see the final output.

Parent Workflow: Run Details

Hope this helps.

Happy Coding.

Regards,
Jaliya