OAuth2 with grant type "client_credentials" is a perfect example of where using custom authentication with token refresh is necessary: when the endpoint is not quite OAuth2, but you still need to get an access token and refresh it. Import Achievers 4.json to see an example where this is implemented.

First, you need to configure the initial token exchange. To do this, create a resource with the Resource Type set to PROVISION AUTH VALIDATION. Do not use ON PROVISION, as it will not set the authentication.time property. 

Configure parameters to save the expires_in and access_token that get returned from this call: 

Next create a new resource with the Resource Type set to ON REFRESH. In this example, the call to refresh the token is the same as the call to get the token the first time, so this resource will by identical to the first one. 

How does it work? 

In this example, you need the two API calls: one with a Resource Type of PROVISION AUTH VALIDATION, and another with ON REFRESH. Beyond that, it is all about the configuration properties:

You need to have authentication.time (this should get added for you) and expires_in. Make sure these are spelled exactly like this example.

When you provision, it will set the authentication.time through the PROVISION AUTH VALIDATION resource. The expires_in will be set by the response of that call.

The next time a call is made our system will check if (expires_in + authentication.time > now). If it is, it will call ON REFRESH, which will restart the process.