AnyRetry

A simple CSharp library for retrying operations with backoff and async support.

Description

AnyRetry allows you to retry operations that may fail such as database operations, network or anything which may throw an unexpected temporary exception. It supports auto-backoff using different available algorithms which is real handy for retrying network operations. Support is available for .Net Framework 4+ and .Net Standard 2.0+

Installation

Install AnyRetry from the Package Manager Console:

PM> Install-Package AnyRetry

Usage

Basic usage would be to retry execution of a method if it throws an exception. If any exception is thrown, it will retry up to 10 times every 5 seconds (configurable). If it exceeds the maximum number of retries, a RetryTimeoutException will be thrown.

using AnyRetry;

var maxRetries = 10;
var retryEvery = TimeSpan.FromSeconds(5);
Retry.Do(() =>
{
    DoMyNetworkOperation();
}, retryEvery, maxRetries);

To only retry if a specific known exception is thrown, but you want to abort if any other type of exception is thrown:

var maxRetries = 10;
var retryEvery = TimeSpan.FromSeconds(5);
Retry.Do(() =>
{
    DoMyNetworkOperation();
}, retryEvery, maxRetries, typeof(SocketException), typeof(IOException));

To use a backoff schedule (to increase your retry timeouts exponentially for example) simply specify the retry policy:

var maxRetries = 10;
var retryEvery = TimeSpan.FromSeconds(5);
Retry.Do(() =>
{
    DoMyNetworkOperation();
}, retryEvery, maxRetries, RetryPolicy.ExponentialBackoff);

Retry Policies

There are 3 types of policies available: StaticDelay, ExponentialBackoff, EasedBackoff.

StaticDelay specifies that the retry time is always the same. ExponentialBackoff will multiply the retryEvery exponentially on every failure (a maximum can also be specified). EasedBackoff allows you to choose a standard easing algorithm, such as ExponentialEaseOut or QuadraticEaseOut for example.

Specifying policy options:

var maxRetries = 10;
var retryEvery = TimeSpan.FromSeconds(5);
var policyOptions = new RetryPolicyOptions { 
    EasingFunction = EasingFunction.QuadraticEaseOut,
    MaxRetryInterval = TimeSpan.FromSeconds(30),
    // optional: specify we want to ease over 5 retries, not the default of maxRetries=10
    MaxRetrySteps = 5
};
Retry.Do(() =>
{
    DoMyNetworkOperation();
}, retryEvery, maxRetries, RetryPolicy.EasedBackoff, policyOptions);

If you wish to specify easing over a period shorter than the maximum number of retries, use the MaxRetrySteps option and specify a value shorter than the maximum number of retries. When it hits this limit it will plateau and use the MaxRetryInterval for the remaining retries.

Asynchronous usage

Async usage is identical to the synchronous examples:

var maxRetries = 10;
var retryEvery = TimeSpan.FromSeconds(5);
await Retry.DoAsync(async () =>
{
    await DoMyNetworkOperationAsync();
}, retryEvery, maxRetries);

Advanced tips

If you need access to the retry information, you can specify access as follows:

var maxRetries = 10;
var retryEvery = TimeSpan.FromSeconds(5);
 Retry.Do((retryIteration, maxRetryCount) =>
{
    Console.WriteLine($"Retry #: {retryIteration}");
    Console.WriteLine($"MaxRetries #: {maxRetryCount}");
    DoMyNetworkOperation();
}, retryEvery, maxRetries);

If you want to run some code when a retry fails, use the onFailure handler:

var maxRetries = 10;
var retryEvery = TimeSpan.FromSeconds(5);
 Retry.Do(() =>
{
    DoMyNetworkOperation();
}, retryEvery, maxRetries, RetryPolicy.StaticDelay, RetryPolicyOptions.None, (retryIteration, maxRetryCount) => {
  // add your custom error code here
});

A rarely useful feature is being able to always retry if a condition is true, and if a condition is false it will retry up to the maximum number of retries. This can be useful if you want to always retry based on some condition like a status check, but if that condition isn't met to retry until failure.

var maxRetries = 1;
var retryEvery = TimeSpan.FromMilliseconds(100);
var i = 0;
Retry.Do(() =>
{
    i++;
    DoMyNetworkOperation();
}, retryEvery, 
    maxRetries, 
    RetryPolicy.StaticDelay, 
    RetryPolicyOptions.None, 
    (retryIteration, maxRetryCount) => {},
    () => {
        // this must return true otherwise it will retry forever!
        // the result of this is it will retry until i is 10, no matter the maxRetries value.
        return i != 10;
    }
);