The wait gem executes a block until there's a result. Useful for blocking script execution until:

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

Add to your Gemfile:

gem 'wait', :git => '[email protected]:foursquare/wait.git'

wait = Wait.new
# => #<Wait>
wait.until { Time.now.sec.even? }
# Rescued exception while waiting: Wait::NoResultError: result was false
# Attempt 1/5 failed, delaying for 1s
# => 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
# Rescued exception while waiting: Wait::NoResultError: result was nil
# Attempt 1/5 failed, delaying for 1s
# Rescued exception while waiting: RuntimeError: RuntimeError
# Attempt 2/5 failed, delaying for 2s
# => "foo"

:attempts

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

:timeout

Seconds until the block times out. Default is 15.

:delay

Initial (grows exponentially) delay (in seconds) to wait in between attempts. Default is 1.

:rescue

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

:debug

If true, logs debugging output. Default is false.

RDoc-generated documentation available here.