introduce explicit factor to exponent backoff strategy

[myronmarston]

Looks good besides the mutation concern.

[myronmarston]

One other thought: if you dislike the interface of the exponential method that is forced upon you by backwards compatibility concerns, you could just create a new method, such as exponential_with_factor or exponential_with_base or whatever and make that method have whatever argument interface you want. Then exponential can be left alone.

I have no preference for which direction you take (changing exponential or defining a new method) but thought I'd mention it as an option since you expressed a dislike for the interface.

[vadim-ex]

Thank you. In this particular case duplicating method is not an option. The purpose of breaking compatibility is to force change of bad code, and an additional method would defeat it.

[vadim-ex]

PTAL

[vadim-ex]

PTAL

[myronmarston]

LGTM