Polly.Contrib.WaitAndRetry examples

oldway.cs

var transientErrors = new HashSet<WebExceptionStatus>(new[]
{
    WebExceptionStatus.ConnectFailure,
    WebExceptionStatus.ConnectionClosed,
    WebExceptionStatus.KeepAliveFailure,
    WebExceptionStatus.Pending,
    WebExceptionStatus.PipelineFailure,
    WebExceptionStatus.ProtocolError,
    WebExceptionStatus.ReceiveFailure,
    WebExceptionStatus.RequestCanceled,
    WebExceptionStatus.SecureChannelFailure,
    WebExceptionStatus.SendFailure,
    WebExceptionStatus.Timeout
});

var retryTimes = new List<TimeSpan>
{
    TimeSpan.FromMilliseconds(0),
    TimeSpan.FromMilliseconds(50),
    TimeSpan.FromMilliseconds(100),
    TimeSpan.FromMilliseconds(150)
};

var retryPolicy = Policy
    .Handle<WebException>(ex => transientErrors.Contains(ex.Status))
    .OrInner<WebException>(ex => transientErrors.Contains(ex.Status))
    .Or<TimeoutException>()
    .OrInner<TimeoutException>()
    .WaitAndRetry(retryTimes,
        (exception, timeSpan, retryCount, context) =>
        {
            LogTo.Warning(
                exception,
                "WARNING: Unable to save to Raven, will retry after {RetryTimeSpan}, Retry attempt {RetryCount}",
                timeSpan,
                retryCount);
        });

polly examples.cs

var constant = Backoff.ConstantBackoff(TimeSpan.FromMilliseconds(100), retryCount: 5, fastFirst: true);

var constantPolicy = Policy
    .Handle<FooException>()
    .WaitAndRetryAsync(constant);

var linear = Backoff.LinearBackoff(TimeSpan.FromMilliseconds(50), retryCount: 5, fastFirst: true);

var linearPolicy = Policy
    .Handle<FooException>()
    .WaitAndRetryAsync(linear);

var exponential = Backoff.ExponentialBackoff(TimeSpan.FromMilliseconds(20), retryCount: 5, fastFirst: true);

var exponentialPolicy = Policy
    .Handle<FooException>()
    .WaitAndRetryAsync(exponential);

var jittered = Backoff.DecorrelatedJitterBackoffV2(
    medianFirstDelay: TimeSpan.FromMilliseconds(50) 
    retryCount: 5, 
    fastFirst: true);

var jitteredPolicy = Policy
    .Handle<FooException>()
    .WaitAndRetryAsync(jittered);

Hi,

Should the transientErrors contain the WebExceptionStatus.NameResolutionFailure? I tried the list and upon disconnecting the internet I get this status code of NameResolutionFailure.

Regards, Haris

It definitely sounds like it should @HarisMQ. Good catch. The code above only deals with intermittent connectivity issues to upstream services and doesn't account for issues like DNS name resolution. You could add it or add a specific policy for things that may take longer to resolve and then use Policy.Wrap to combine them.

It's also worth exploring the circuit-breaker pattern and the support for that in Polly as you might want to break on something like your internet connection being down so you can provide better messaging back to your users.