Tries
Solidify your code and retry on petty exceptions.
Tries lets you retry a block of code multiple times, which is convenient for example when communicating with external APIs that might return an error the one second but work fine the next.
You can specify exactly how often the block of code is retried and which exceptions are caught.
Requirements
Tests run on Ruby >= 2.5 is tested, older versions might work as well.
Installation
Add this line to your application's Gemfile:
gem 'tries'
And then execute:
$ bundle
Or install it yourself as:
$ gem install tries
Usage
3.tries on: Timeout::Error do
Mechanize.new.get 'https://www.google.com/'
end
Detailed usage
Helper code to explain how it works
FooError = Class.new(StandardError)
BarError = Class.new(StandardError)
@error_counter = 0
def method_that_raises_exception
@error_counter += 1
puts "Counter is #{@error_counter}"
case @error_counter
when 1 then raise FooError, 'retry'
when 2 then raise FooError, 'retry'
when 3 then raise BarError
when 4 then raise StandardError
end
puts 'You made it through!'
end
Rescue all errors
4.tries do
method_that_raises_exception
end
# => Counter is 1
# => Counter is 2
# => Counter is 3
# => Counter is 4
# => Counter is 5
# => You made it through!
Rescue a specific error
3.tries on: FooError do
method_that_raises_exception
end
# => Counter is 1
# => Counter is 2
# => Counter is 3
# => BarError
Rescue multiple errors
3.tries on: [FooError, BarError] do
method_that_raises_exception
end
# => Counter is 1
# => Counter is 2
# => Counter is 3
# => Counter is 4
# => StandardError
Rescue error on condition
3.tries if: ->(error) { error.message == 'retry' } do
method_that_raises_exception
end
# => Counter is 1
# => Counter is 2
# => Counter is 3
# => BarError
Delay execution after error
delay
is in seconds, fractions are possible
Static delay
4.tries delay: 1.5 do
method_that_raises_exception
end
# => Counter is 1
# waits 1.5 seconds...
# => Counter is 2
# waits 1.5 seconds...
# => Counter is 3
# waits 1.5 seconds...
# => Counter is 4
# waits 1.5 seconds...
# => Counter is 5
# => You made it through!
Incremental delay
4.tries delay: 1.5, incremental: true do
method_that_raises_exception
end
# => Counter is 1
# waits 1.5 seconds...
# => Counter is 2
# waits 3 seconds...
# => Counter is 3
# waits 4.5 seconds...
# => Counter is 4
# waits 6 seconds...
# => Counter is 5
# => You made it through!
Callback on error
You can set a method or Proc to be called every time an exception occurs. Either set it globally in an initializer, e.g. to log all exceptions to a service like Airbrake, or locally when calling tries
. If both a global callback and a local callback are set, both are called, the global one first.
Global callback
# config/initializers/tries.rb
Tries.configure do |config|
config.on_error = lambda do |exception, attempts, next_delay|
puts "Whow, a #{exception.class} just occurred! It was attempt nr. #{attempts} to do whatever I was doing."
if next_delay
puts "I'm gonna wait #{next_delay} seconds and try again."
else
puts "A delay was not configured so I'm gonna go for it again immediately."
end
end
end
3.tries delay: 0.5, incremental: true do
method_that_raises_exception
end
# => Counter is 1
# => Whow, a FooError just occurred! It was attempt nr. 1 to do whatever I was doing.
# => I'm gonna wait 0.5 seconds and try again.
# waits 0.5 seconds...
# => Counter is 2
# => Whow, a FooError just occurred! It was attempt nr. 2 to do whatever I was doing.
# => I'm gonna wait 1.0 seconds and try again.
# waits 1 second...
# => Counter is 3
# => Whow, a BarError just occurred! It was attempt nr. 3 to do whatever I was doing.
# => I'm gonna wait 1.5 seconds and try again.
# waits 1.5 seconds...
# => Counter is 4
# => StandardError
When using Rails, a global callback also lets you effectively disable Tries in development environment:
# config/initializers/tries.rb
Tries.configure do |config|
config.on_error = lambda do |exception, attempts, next_delay|
raise exception if Rails.env.development?
end
end
Local callback
callback = lambda do |exception, attempts, next_delay|
puts "Local callback! Exception: #{exception.class}, attempt: #{attempts}, next_delay: #{next_delay}"
end
3.tries delay: 0.5, incremental: true, on_error: callback do
method_that_raises_exception
end
# => Counter is 1
# => Local callback! Exception: FooError, attempt: 1, next_delay: 0.5
# waits 0.5 seconds...
# => Counter is 2
# => Local callback! Exception: FooError, attempt: 2, next_delay: 1.0
# waits 1 second...
# => Counter is 3
# => Local callback! Exception: BarError, attempt: 3, next_delay: 1.5
# waits 1.5 seconds...
# => Counter is 4
# => StandardError
Contributing
- Fork it
- Create your feature branch (
git checkout -b my-new-feature
) - Commit your changes (
git commit -am 'Add some feature'
) - Push to the branch (
git push origin my-new-feature
) - Create new Pull Request
Support
If you like this project, consider buying me a coffee! :)