Runs a code block, and retries it when an exception occurs. It's great when working with flakey webservices (for example).
It's configured using four optional parameters :tries, :on, :sleep, :matching, :ensure and
runs the passed block. Should an exception occur, it'll retry for (n-1) times.
Should the number of retries be reached without success, the last exception will be raised.
Open an URL, retry up to two times when an OpenURI::HTTPError occurs.
require "open-uri"
Retryable.retryable(:tries => 3, :on => OpenURI::HTTPError) do
xml = open("http://example.com/test.xml").read
endDo something, retry up to four times for either ArgumentError or
TimeoutError exceptions.
Retryable.retryable(:tries => 5, :on => [ArgumentError, TimeoutError]) do
# some crazy code
endEnsure that block of code is executed, regardless of whether an exception was raised. It doesn't matter if the block exits normally, if it retries to execute block of code, or if it is terminated by an uncaught exception -- the ensure block will get run.
f = File.open("testfile")
ensure_cb = Proc.new do |retries|
puts "total retry attempts: #{retries}"
f.close
end
Retryable.retryable(:ensure => ensure_cb) do
# process file
end:tries => 2, :on => StandardError, :sleep => 1, :matching => /.*/, :ensure => Proc.new { }By default Retryable waits for one second between retries. You can change this and even provide your own exponential backoff scheme.
Retryable.retryable(:sleep => 0) { } # don't pause at all between retries
Retryable.retryable(:sleep => 10) { } # sleep ten seconds between retries
Retryable.retryable(:sleep => lambda { |n| 4**n }) { } # sleep 1, 4, 16, etc. each tryYou can also retry based on the exception message:
Retryable.retryable(:matching => /IO timeout/) do |retries, exception|
raise "yo, IO timeout!" if retries == 0
endYour block is called with two optional parameters: the number of tries until now, and the most recent exception.
Retryable.retryable do |retries, exception|
puts "try #{retries} failed with exception: #{exception}" if retries > 0
pick_up_soap
endRetryble.enabled?
=> true
Retryble.disable
Retryble.enabled?
=> falseTo add retryable to both Kernel and the global namespace:
require "retryable/core_ext/kernel"
require "open-uri"
Kernel.retryable(:tries => 3, :on => OpenURI::HTTPError) do
xml = open("http://example.com/test.xml").read
end
# Or..
retryable(:tries => 3, :on => OpenURI::HTTPError) do
xml = open("http://example.com/test.xml").read
endInstall the gem:
$ gem install retryableAdd it to your Gemfile:
gem 'retryable'