Anticipate¶ ↑

About¶ ↑

Anticipate is a fluent interface for retrying blocks of code:

sleeping(0.1).seconds.between_tries.failing_after(20).tries do

  # Calls block every 0.1 seconds until it stops raising errors

end

Including the Anticipate module into your class gives you:

failing_after(3).tries {}
sleeping(0.1).seconds.between_tries {}
sleeping(123).seconds.between_tries.failing_after(456).tries {}

Blocks should contain an assertion, i.e. raise a descriptive error if some condition is unsatisfied. On the last iteration, any error will be wrapped in an Anticipate::TimeoutError and re-raised.

The first try is attempted immediately, there is no sleep before the first yield.

Defining your own timings¶ ↑

If lots of your code needs to wait for things to happen, you might consider defining your own timing module, e.g:

module Timing
  include Anticipate

  def very_soon
    sleeping(0.1).seconds.between_tries.failing_after(10).tries do
      yield
    end
  end

  def eventually
    sleeping(2).seconds.between_tries.failing_after(5).tries do
      yield
    end
  end
end

…that way you can adjust timing details in one place as the system grows.

Alternatives¶ ↑

I’m aware of a couple of gems performing the begin-rescue-sleep-retry dance, namely ‘retry’ and ‘attempt’. The aim of this library is to offer more expressive syntax.