/// <summary>
/// Initializes a new instance of the RetryPolicy class with the specified number of retry attempts and parameters defining the progressive delay between retries.
/// </summary>
/// <param name="errorDetectionStrategy">The <see cref="ITransientErrorDetectionStrategy"/> that is responsible for detecting transient conditions.</param>
/// <param name="retryStrategy">The retry strategy to use for this retry policy.</param>
public RetryPolicy(ITransientErrorDetectionStrategy errorDetectionStrategy, RetryStrategy retryStrategy)
{
ErrorDetectionStrategy = errorDetectionStrategy;
if (errorDetectionStrategy == null)
{
throw new InvalidOperationException("The error detection strategy type must implement the ITransientErrorDetectionStrategy interface.");
}
RetryStrategy = retryStrategy;
}
/// <summary>
/// Repetitively executes the specified action while it satisfies the current retry policy.
/// </summary>
/// <typeparam name="TResult">The type of result expected from the executable action.</typeparam>
/// <param name="func">A delegate representing the executable action which returns the result of type R.</param>
/// <returns>The result from the action.</returns>
public async virtual Task <TResult> ExecuteAction <TResult>(Func <Task <TResult> > func)
{
int retryCount = 0;
TimeSpan delay = TimeSpan.Zero;
Exception lastError;
var shouldRetry = RetryStrategy.GetShouldRetry();
for (; ;)
{
lastError = null;
try
{
return(await func().ConfigureAwait(false));
}
catch (Exception ex)
{
lastError = ex;
if (!(ErrorDetectionStrategy.IsTransient(lastError) && shouldRetry(retryCount++, lastError, out delay)))
{
throw;
}
}
// Perform an extra check in the delay interval. Should prevent from accidentally ending up with the value of -1 that will block a thread indefinitely.
// In addition, any other negative numbers will cause an ArgumentOutOfRangeException fault that will be thrown by Thread.Sleep.
if (delay.TotalMilliseconds < 0)
{
delay = TimeSpan.Zero;
}
OnRetrying(retryCount, lastError, delay);
if (retryCount > 1 || !RetryStrategy.FastFirstRetry)
{
await Task.Delay(delay).ConfigureAwait(false);
}
}
}
