Exponential Backoff

This is a Dart port of the exponential backoff algorithm from Google's HTTP Client Library for Java.

Exponential backoff is an algorithm that uses feedback to multiplicatively decrease the rate of some process, in order to gradually find an acceptable rate. The retries exponentially increase and stop increasing when a certain threshold is met.

Features

• Exponentially backoff operations
• Retries

Getting started

Add the package to your codebase

dart pub add backoff

Usage

1. Import the code

import 'package:backoff/backoff.dart';

2. Create an instance of ExponentialBackOff

ExponentialBackOff backOff = ExponentialBackOff();

You can customize the parameters during instantiation:

ExponentialBackOff customBackOff = ExponentialBackOff(
  initialIntervalMillis: 1000,
  randomizationFactor: 0.2,
  multiplier: 2.0,
  maxIntervalMillis: 60000,
  maxElapsedTimeMillis: 180000,
);

3. Use the backoff strategy in your retry logic

int backOffMillis = backOff.nextBackOffMillis();

if (backOffMillis == BackOff.STOP) {
  // Do not retry operation
} else {
  // Sleep for backOffMillis milliseconds and retry operation
  await Future.delayed(Duration(milliseconds: backOffMillis));
  // Retry operation here
}

4. Reset the backoff

If you want to reset the backoff to its initial state, you can use the reset method:

backOff.reset();

5. Additional Information

Available Properties You can retrieve the values of various properties:

print("Initial Interval: ${backOff.getInitialIntervalMillis()} milliseconds");
print("Randomization Factor: ${backOff.getRandomizationFactor()}");
print("Current Interval: ${backOff.getCurrentIntervalMillis()} milliseconds");
print("Multiplier: ${backOff.getMultiplier()}");
print("Max Interval: ${backOff.getMaxIntervalMillis()} milliseconds");
print("Max Elapsed Time: ${backOff.getMaxElapsedTimeMillis()} milliseconds");

Elapsed Time If you want to know the elapsed time since the backoff started:

int elapsedMillis = backOff.getElapsedTimeMillis();
print("Elapsed Time: $elapsedMillis milliseconds");

Constants

The BackOff class provides two constants for special cases:

• BackOff.ZERO_BACKOFF: A fixed backoff policy with zero wait time.
• BackOff.STOP_BACKOFF: A fixed backoff policy that always returns BackOff.STOP, indicating that the operation should not be retried.

These can be used when you have specific requirements for immediate retries or no retries.

Contributing

• I would like to keep this library as small as possible.
• Please don't send a PR without opening an issue and discussing it first.
• If proposed change is not a common use case, I will probably not accept it.