The wait gem executes a block until there's a valid (by default, truthy) result. Useful for blocking script execution until:

• an HTTP request was successful
• a port has opened
• a process has started
• etc.

Add to your Gemfile:

gem "wait", "~> 0.5.3"

wait = Wait.new
# => #<Wait>
wait.until { Time.now.sec.even? }
# [Counter] attempt 1/5
# [Tester]  result: false
# [Rescuer] rescued: Wait::ResultInvalid
# [Raiser]  not raising: Wait::ResultInvalid
# [Delayer] delaying for 1s
# [Counter] attempt 2/5
# [Tester]  result: true
# => true

If you wish to handle an exception by attempting the block again, pass one or an array of exceptions with the :rescue option.

wait = Wait.new(:rescue => RuntimeError)
# => #<Wait>
wait.until do |attempt|
  case attempt
  when 1 then nil
  when 2 then raise RuntimeError
  when 3 then "foo"
  end
end
# [Counter] attempt 1/5
# [Tester]  result: nil
# [Rescuer] rescued: Wait::ResultInvalid
# [Raiser]  not raising: Wait::ResultInvalid
# [Delayer] delaying for 1s
# [Counter] attempt 2/5
# [Rescuer] rescued: RuntimeError
# [Raiser]  not raising: RuntimeError
# [Delayer] delaying for 1s
# [Counter] attempt 3/5
# [Tester]  result: "foo"
# => "foo"

attempts

Number of times to attempt the block. Default is 5.

timeout

Seconds until the block times out. Default is 15.

delay

Seconds to delay in between attempts. Default is 1.

rescue

One or an array of exceptions to rescue. Default is nil.

debug

If true, debug logging is enabled. Default is false.

logger

Ruby logger used. Default is Wait::BaseLogger.

counter

Strategy used to count attempts. Default is Wait::BaseCounter.

delayer

Strategy used to delay in between attempts. Default is Wait::RegularDelayer.

rescuer

Strategy used to rescue exceptions. Default is Wait::BaseRescuer.

tester

Strategy used to test the result. Default is Wait::TruthyTester.

raiser

Strategy used to raise specific exceptions. Default is Wait::SignalRaiser.

RDoc-generated documentation available here.