RetryHelper

This is a generic helper to help try some action until given condition is met.

Usage

Write retry logic for operations like web request or file operation in a more readable way rather than a try-catch nested in a loop. You can specify end conditions based on return value or exception, config the retry interval, maximum retry count and maximum retry time flexibly, and more.

Examples:

One-line sample

RetryHelper.Instance.Try(() => TryDoSomething()).UntilNoException();

Example 1: Retry until I get a return value < 0.1 from the method TryGetSomething.

// Basic usage
RetryHelper.Instance.Try(() => TryGetSomething()).Until(result => result < 0.1);

// Get the result from the retried method
var resultSmallEnough = RetryHelper.Instance.Try(() => TryGetSomething()).Until(result => result < 0.1);

// Specify interval
RetryHelper.Instance.Try(() => TryGetSomething()).WithTryInterval(100).Until(result => result < 0.1);

// Specify max try count, will throw TimeoutException if exceeded
RetryHelper.Instance.Try(() => TryGetSomething()).WithMaxTryCount(20).Until(result => result < 0.1);

// Can also constrain the total try time
RetryHelper.Instance.Try(() => TryGetSomething()).WithTimeLimit(TimeSpan.FromSeconds(10)).Until(result => result < 0.1);

// Specify the extra success/fail/timeout action
RetryHelper.Instance.Try(() => TryGetSomething())
    .WithMaxTryCount(20)
    .OnSuccess(result => Trace.TraceInformation(string.Format("Get result {0}.", result)))
    .OnFailure(result => Trace.TraceWarning(string.Format("Try failed. Got {0}", result)))
    .OnTimeout(lastResult => Trace.TraceError("Did not get result under 0.1 in 20 times."))
    .Until(result => result < 0.1);

// Also get the tried count.
RetryHelper.Instance.Try(() => TryGetSomething())
    .WithMaxTryCount(20)
    .OnSuccess((result, triedCount) => Trace.TraceInformation(string.Format("Get expected result {0} after {1} times.", result, triedCount)))
    .OnFailure((lastResult, triedCount) => Trace.TraceWarning(string.Format("Try failed after {0} times. Got {1}", triedCount, lastResult)))
    .OnTimeout((lastResult, triedCount) => Trace.TraceError(string.Format("Did not get result under 0.1 in {0} times.", triedCount)))
    .Until(result => result < 0.1);

• OnSuccess: Executed after the condition is met.
• OnFailure: Executed after each failed attempt and before the next attempt.
• OnTimeout: Executed after all allowed attempts are failed.

Example 2: Retry method TryDoSomething until there's no exception thrown.

// Retry on any (non-fatal) exception
RetryHelper.Instance.Try(() => TryDoSomething()).UntilNoException();

// Retry on specific exception
RetryHelper.Instance.Try(() => TryDoSomething()).UntilNoException<ApplicationException>();

// Lambda can be simplified in this case
RetryHelper.Instance.Try(TryDoSomething).UntilNoException();

Change the global default settings

RetryHelper.Instance.DefaultMaxTryCount = 3;
RetryHelper.Instance.DefaultMaxTryTime = TimeSpan.FromSeconds(10);
RetryHelper.Instance.DefaultTryInterval = TimeSpan.FromMilliseconds(100);

Get another RetryHelper instance with custom TraceSource and separate configration

var retryHelper = new RetryHelper(new TraceSource("MyTraceSource"))
{
    DefaultMaxTryCount = 10,
    DefaultMaxTryTime = TimeSpan.FromSeconds(30),
    DefaultTryInterval = TimeSpan.FromMilliseconds(500)
}

LICENSE

Apache 2.0 License