When indexing on a cluster, the database status page in the admin consoles starts failing. I'm indexing a timestamp on indexing priority 2 in a billion documents and this may take a week or two.
What is the best way to get an idea about the indexing progress?
Use the Management API's GET /manage/v2/databases/{id|name}?view=status page. You'll send an HTTP request, such as:
http://localhost:8002/manage/v2/databases/Documents?view=status
to check out the Documents database on localhost. One part of the information retrieved will be reindexing status.