retry

Retry an execution that terminates with an error

Overview

The Retry library provides basic retry functionality with a clear and simple API. It supports:

Retrying on any error
Retrying on a specific error
Retrying based on a list of possible errors
Retrying once or many times
Backoff intervals that allow delaying between retries

Examples

Retry on Any Error

Any error will cause the block to retry. The block will only retry once.

tries = 0

Retry.() do
  tries += 1

  # RuntimeError will be raised during the first iteration
  # The block will be executed once again without raising an error
  # for a total of 2 executions
  if tries == 1
    raise RuntimeError
  end
end

puts tries
# => 2

Retry on a Specific Error

The block will be retried only if the specified error is raised in the block. The block will only retry once.

SomeError = Class.new(RuntimeError)

tries = 0

Retry.(SomeError) do
  tries += 1

  puts tries

  # SomeError will be raised during the first iteration
  # and the block will be executed once again
  if tries == 1
    raise SomeError
  end

  # Will raise RuntimeError in the second iteration
  # RuntimeError is not retried, and so the program
  # terminates with here RuntimeError
  raise RuntimeError
end

# => 1
# => 2
# => RuntimeError

Retry on Multiple Specific Errors

The block will be retried if any of the the specified errors are raised in the block. The block will only retry once.

SomeError = Class.new(RuntimeError)
SomeOtherError = Class.new(RuntimeError)

tries = 0

Retry.(SomeError, SomeOtherError) do
  tries += 1

  puts tries

  # SomeOtherError will be raised during the first iteration
  # and the block will be executed once again
  if tries == 1
    raise SomeOtherError
  end

  # Will raise RuntimeError in the second iteration
  # RuntimeError is not retried, and so the program
  # terminates here with RuntimeError
  raise RuntimeError
end

# => 1
# => 2
# => RuntimeError

Retry and Back Off

The millisecond_intervals parameter can be used without specifying a specific error, when specifying a specific error, or when specifying a list of possible errors.

The block will be retried up to the number of delay intervals specified.

SomeError = Class.new(RuntimeError)
SomeOtherError = Class.new(RuntimeError)

tries = 0

Retry.(SomeError, SomeOtherError, millisecond_intervals: [100, 200]) do
  tries += 1

  puts tries

  raise SomeError
end

# => 1 (first attempt)
# => 2 (second attempt, after 100 ms delay)
# => 3 (third attempt, after 200 ms delay)
# => SomeError

License

The retry library is released under the MIT License.

evt-retry

Development

Runtime