Invoke a private on‑prem, Compute Engine, GKE, or other endpoint

Calling or invoking a private on‑premises, Compute Engine, Google Kubernetes Engine (GKE), or other Google Cloud endpoint from Workflows is done through an HTTP request. The most common HTTP request methods have a call shortcut (such as http.get and, but you can make any type of HTTP request by setting the call field to http.request and specifying the type of request using the method field. For more information, see Make an HTTP request.

Enable IAP

You must enable Identity-Aware Proxy (IAP) for the private endpoint so that Workflows can invoke the endpoint. IAP is used to enforce access control policies, and it lets you establish a central authorization layer for applications accessed by HTTPS, so that you can use an application-level access control model instead of relying on network-level firewalls. For more information, see the IAP overview and the following:

Use a service account with the required permissions

When making requests to other Google Cloud services, your workflow must be associated with a service account that has been granted one or more Identity and Access Management (IAM) roles containing the required permissions to access the requested resources. To learn what service account is associated with an existing workflow, see Verify a workflow's associated service account.

When setting up a service account, you associate the requesting identity with the resource you wish to give it access to—you make the requesting identity a principal, or user, of the resource—and then assign it the appropriate role. The role defines what permissions the identity has in the context of the resource. When an application or resource is protected by IAP, it can only be accessed through the proxy by principals who have the correct role.

For example, after authentication, IAP applies the relevant allow policy to check if the principal is authorized to access the requested resource. If the principal has the IAP-secured Web App User role (roles/iap.httpsResourceAccessor) on the console project where the resource exists, they're authorized to access the application.

You can configure access to your IAP-secured resource through the IAP page by adding the Workflows service account as a principal. For more information, see Managing access to IAP-secured resources.

Add authentication information to your workflow

By default, HTTP requests do not contain identity or access tokens for security reasons. You must explicitly add authentication information to your workflow definition. When making requests to a private endpoint, use OIDC to authenticate through IAP.

To make an HTTP request using OIDC, add an auth section to the args section of your workflow's definition, after you specify the URL.


  - step_A:
      call: http.get
              someValue: "Hello World"
              anotherValue: 123
              type: OIDC
              audience: OIDC_AUDIENCE


        "step_A": {
          "call": "http.get",
          "args": {
            "url": "",
            "body": {
              "someValue": "Hello World",
              "anotherValue": 123
            "auth": {
              "type": "OIDC",
              "audience": "OIDC_AUDIENCE"

You can use the audience parameter to specify the OIDC audience for the token. When invoking an IAP-enabled endpoint, you must specify the OAuth 2.0 client ID that you have configured for your application. This can be obtained from the Credentials page.

What's next