What is the Correct way of logging before Retry using Polly

Question

I'm attempting to log something before retrying. What is the correct syntax of logging info before retry happens?

Here's a sample code similar to my actual code:

var policy = Polly.Policy
    .Handle<SomeExceptionType>()
    .WaitAndRetryAsync(
    retryCount: this.maxRetryCount,
    sleepDurationProvider: (_, e, context) =>
    {
        var waitTimeSpan = TimeSpan.FromSeconds(1);
        if (e != null && e is SomeExceptionType someException)
        {
            var retryAfterFromException = someException.Headers?.RetryAfter.Delta;
            if (retryAfterFromException > TimeSpan.Zero)
            {
                waitTimeSpan = retryAfterFromException.GetValueOrDefault();
            }
        }
    
        return waitTimeSpan;
    },
    onRetryAsync: (e, timeSpan, retryCount) => 
       this.logger.LogInfo($"Request failed with {result.Result.StatusCode}. Waiting {timeSpan} before next retry. Retry attempt {retryCount}"));

This gives syntax error because LogInfo returns void. What's the right approach of logging?

Please be aware of this `result.Result.StatusCode` code might throw `NullReferenceException` if an Exception has been thrown during the request. Please use the [null-conditional operator](https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/operators/member-access-operators#null-conditional-operators--and-): `result?.Result?.StatusCode` — Peter Csala, Jun 30 '22 at 14:12

score 2 · Accepted Answer · answered Jun 30 '22 at 14:06

Based on your sleepDurationProvider delegate, you try to use this overload:

public static AsyncRetryPolicy WaitAndRetryAsync(
   this PolicyBuilder policyBuilder, 
   int retryCount,
   Func<int, Exception, Context, TimeSpan> sleepDurationProvider, 
   Func<Exception, TimeSpan, int, Context, Task> onRetryAsync)

That means the expected onRetryAsync should look like this:

(exception, sleepDuration, retry, context) => 
{
  this.logger.LogInfo(...);
  return Task.CompletedTask;
}

user1672994 · Answer 2 · 2022-06-30T15:22:44.120

1

Change it to

onRetryAsync: (e, timeSpan, retryCount, context) => { 
   this.logger.LogInfo($"Request failed with {result.Result.StatusCode}. Waiting 
    {timeSpan} before next retry. Retry attempt {retryCount}"); 
   return Task.CompletedTask; 
});`

as onRetryAsync expects a Task return type

edited Jun 30 '22 at 15:22

answered Jun 30 '22 at 13:09

user1672994

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Unfortunately there is no such overload of `WaitAndRetryAsync` which anticipates this `onRetryAsync` delegate and the OP's `sleepDurationProvider` function. – Peter Csala Jun 30 '22 at 14:07

What is the Correct way of logging before Retry using Polly

2 Answers2