There is an API that Sidekiq provides for programmatically querying the state of the various queues under Sidekiq's control.
If you don't want to expose the web interface to the world then using this API is a must.
Here is some sample code for finding how many items are currently in the retry queue, if you have too many jobs constantly failing there is likely something you need to change in your worker.
retry_queue = Sidekiq::RetrySet.new retry_queue.size
I would encourage you to read more about the API.