As HIgher Logic Partners, we use Higher Logic's API to index your organization's discussion forum content. We'll need your organization's HLIAMKey to get started (you can get this from your Higher Logic handler/representative). We get metadata over the webservice that we can use as filters in your search like the names of the forums, dates, and authors.
More details can be found in this PDF (.83 MB) of Higher Logic's API documentation.
Of note, we also used to connect to Higher Logic competitor Socious until Higher Logic acquired them in early 2017!