Adding support for performing the indexing in real time in case an error occurs when enqueueing the job.

[guilleva]

In my case, sometimes the enqueue fails because or redis timeouts (Redis::TimeoutError: Connection timed out) and because indexing jobs are critical this gives us a way to not lose them and to index the element is real time (which in most of the cases is better than just not indexing them).

[gaffneyc]

Thank you for the pull request and sorry for the long wait on a response. While I like the idea in general it reaches a bit too much into each implementation.

What I would suggest instead is a fallback backend which would be given the appropriate backend.

e.g.

backend = Sunspot::Queue::Fallback::Backend.new(Sunspot::Queue::Sidekiq::Backend.new)
Sunspot.session = Sunspot::Queue::SessionProxy.new(Sunspot.session, backend)

The fallback backend should be able to hold the logic for retrying the enqueue or doing an immediate index should there be a network hiccup.