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Create and run automated event-based workflows by using HTTP webhooks in Azure Logic Apps

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  • 8 minutes to read

With Azure Logic Apps and the built-in HTTP Webhook connector, you can create automated tasks and workflows that subscribe to a service endpoint, wait for specific events, and run based on those events, rather than regularly checking or polling that endpoint.

Here are some example webhook-based workflows:

  • Wait for an item to arrive from an Azure Event Hub before triggering a logic app run.
  • Wait for an approval before continuing a workflow.

This article shows how to use the Webhook trigger and Webhook action so that your logic app can receive and respond to events at a service endpoint.

How do webhooks work?

A webhook trigger is event-based, which doesn't depend on checking or polling regularly for new items. When you save a logic app that starts with a webhook trigger, or when you change your logic app from disabled to enabled, the webhook trigger subscribes to the specified service endpoint by registering a callback URL with that endpoint. The trigger then waits for that service endpoint to call the URL, which starts running the logic app. Similar to the Request trigger, the logic app fires immediately when the specified event happens. The webhook trigger unsubscribes from the service endpoint if you remove the trigger and save your logic app, or when you change your logic app from enabled to disabled.

A webhook action is also event-based and subscribes to the specified service endpoint by registering a callback URL with that endpoint. The webhook action pauses the logic app's workflow and waits until the service endpoint calls the URL before the logic app resumes running. The webhook action unsubscribes from the service endpoint in these cases:

  • When the webhook action successfully finishes
  • If the logic app run is canceled while waiting for a response
  • Before the logic app times out

For example, the Office 365 Outlook connector's Send approval email action is an example of webhook action that follows this pattern. You can extend this pattern into any service by using the webhook action.

For more information, see these topics:

For information about encryption, security, and authorization for inbound calls to your logic app, such as Transport Layer Security (TLS), previously known as Secure Sockets Layer (SSL), or Azure Active Directory Open Authentication (Azure AD OAuth), see Secure access and data - Access for inbound calls to request-based triggers.

Prerequisites

  • An Azure account and subscription. If you don't have an Azure subscription, sign up for a free Azure account.

  • The URL for an already deployed endpoint or API that supports the webhook subscribe and unsubscribe pattern for webhook triggers in logic apps or webhook actions in logic apps as appropriate

  • The logic app where you want to wait for specific events at the target endpoint. To start with the HTTP Webhook trigger, create a blank logic app workflow. To use the HTTP Webhook action, start your logic app with any trigger that you want. This example uses the HTTP trigger as the first step.

Add an HTTP Webhook trigger

This built-in trigger calls the subscribe endpoint on the target service and registers a callback URL with the target service. Your logic app then waits for the target service to send an HTTP POST request to the callback URL. When this event happens, the trigger fires and passes any data in the request along to the workflow.

  1. Sign in to the Azure portal. Open your blank logic app in Logic App Designer.

  2. In the designer's search box, enter http webhook as your filter. From the Triggers list, select the HTTP Webhook trigger.

    Select HTTP Webhook trigger

    This example renames the trigger to HTTP Webhook trigger so that the step has a more descriptive name. Also, the example later adds an HTTP Webhook action, and both names must be unique.

  3. Provide the values for the HTTP Webhook trigger parameters that you want to use for the subscribe and unsubscribe calls.

    In this example, the trigger includes the methods, URIs, and message bodies to use when performing the subscribe and unsubscribe operations.

    Enter HTTP Webhook trigger parameters

    Property Required Description
    Subscription - Method Yes The method to use when subscribing to the target endpoint
    Subscribe - URI Yes The URL to use for subscribing to the target endpoint
    Subscribe - Body No Any message body to include in the subscribe request. This example includes the callback URL that uniquely identifies the subscriber, which is your logic app, by using the @listCallbackUrl() expression to retrieve your logic app's callback URL.
    Unsubscribe - Method No The method to use when unsubscribing from the target endpoint
    Unsubscribe - URI No The URL to use for unsubscribing from the target endpoint
    Unsubscribe - Body No An optional message body to include in the unsubscribe request

    Note: This property doesn't support using the listCallbackUrl() function. However, the trigger automatically includes and sends the headers, x-ms-client-tracking-id and x-ms-workflow-operation-name, which the target service can use to uniquely identify the subscriber.

  4. To add other trigger properties, open the Add new parameter list.

    Add more trigger properties

    For example, if you need to use authentication, you can add the Subscribe - Authentication and Unsubscribe - Authentication properties. For more information about authentication types available for HTTP Webhook, see Add authentication to outbound calls.

  5. Continue building your logic app's workflow with actions that run when the trigger fires.

  6. When you're finished, done, remember to save your logic app. On the designer toolbar, select Save.

    Saving your logic app calls the subscribe endpoint on the target service and registers the callback URL. Your logic app then waits for the target service to send an HTTP POST request to the callback URL. When this event happens, the trigger fires and passes any data in the request along to the workflow. If this operation completes successfully, the trigger unsubscribes from the endpoint, and your logic app continues the remaining workflow.

Add an HTTP Webhook action

This built-in action calls the subscribe endpoint on the target service and registers a callback URL with the target service. Your logic app then pauses and waits for target service to send an HTTP POST request to the callback URL. When this event happens, the action passes any data in the request along to the workflow. If the operation completes successfully, the action unsubscribes from the endpoint, and your logic app continues running the remaining workflow.

  1. Sign in to the Azure portal. Open your logic app in Logic App Designer.

    This example uses the HTTP Webhook trigger as the first step.

  2. Under the step where you want to add the HTTP Webhook action, select New step.

    To add an action between steps, move your pointer over the arrow between steps. Select the plus sign (+) that appears, and then select Add an action.

  3. In the designer's search box, enter http webhook as your filter. From the Actions list, select the HTTP Webhook action.

    Select HTTP Webhook action

    This example renames the action to "HTTP Webhook action" so that the step has a more descriptive name.

  4. Provide the values for the HTTP Webhook action parameters, which are similar to the HTTP Webhook trigger parameters, that you want to use for the subscribe and unsubscribe calls.

    In this example, the action includes the methods, URIs, and message bodies to use when performing the subscribe and unsubscribe operations.

    Enter HTTP Webhook action parameters

    Property Required Description
    Subscription - Method Yes The method to use when subscribing to the target endpoint
    Subscribe - URI Yes The URL to use for subscribing to the target endpoint
    Subscribe - Body No Any message body to include in the subscribe request. This example includes the callback URL that uniquely identifies the subscriber, which is your logic app, by using the @listCallbackUrl() expression to retrieve your logic app's callback URL.
    Unsubscribe - Method No The method to use when unsubscribing from the target endpoint
    Unsubscribe - URI No The URL to use for unsubscribing from the target endpoint
    Unsubscribe - Body No An optional message body to include in the unsubscribe request

    Note: This property doesn't support using the listCallbackUrl() function. However, the action automatically includes and sends the headers, x-ms-client-tracking-id and x-ms-workflow-operation-name, which the target service can use to uniquely identify the subscriber.

  5. To add other action properties, open the Add new parameter list.

    Add more action properties

    For example, if you need to use authentication, you can add the Subscribe - Authentication and Unsubscribe - Authentication properties. For more information about authentication types available for HTTP Webhook, see Add authentication to outbound calls.

  6. When you're finished, remember to save your logic app. On the designer toolbar, select Save.

    Now, when this action runs, your logic app calls the subscribe endpoint on the target service and registers the callback URL. The logic app then pauses the workflow and waits for the target service to send an HTTP POST request to the callback URL. When this event happens, the action passes any data in the request along to the workflow. If the operation completes successfully, the action unsubscribes from the endpoint, and your logic app continues running the remaining workflow.

Trigger and action outputs

Here is more information about the outputs from an HTTP Webhook trigger or action, which returns this information:

Property name Type Description
headers object The headers from the request
body object The object with the body content from the request
status code int The status code from the request
Status code Description
200 OK
202 Accepted
400 Bad request
401 Unauthorized
403 Forbidden
404 Not Found
500 Internal server error. Unknown error occurred.

Connector reference

For more information about trigger and action parameters, which are similar to each other, see HTTP Webhook parameters.

Next steps