private RemoteImageRequest AttemptRetry(RemoteImageRequest failedRequest, string imageUrl, ImageOptions options)
{
if (!failedRequest.IsRequestCompleted)
{
throw new ArgumentException("The request has not completed.", nameof(failedRequest));
}
if (failedRequest.Task.Result.ResultCode == ServiceResultCode.Success)
{
throw new ArgumentException("The request was successful, no retry needed.", nameof(failedRequest));
}
if (failedRequest.Task.Result.ResultCode == ServiceResultCode.ResourceNotFound ||
failedRequest.RetryCounter == this.maxRetryAttempts)
{
return(failedRequest);
}
int retryCounter = failedRequest.RetryCounter;
if (failedRequest.Task.Result.ResultCode != ServiceResultCode.NetworkUnavailable)
{
// If the network is unavailable we will keep retrying until it becomes available.
// It is assumed that the underlying remote client is optimized to handle network status
// so that a call to make repeated remote request is cheap.
retryCounter++;
}
string requestKey = this.GetRequestKey(imageUrl, options);
this.TryRemoveRequest(requestKey);
return(this.TryStartImageRequest(imageUrl, options, retryCounter));
}
private RemoteImageRequest TryStartImageRequest(string imageUrl, ImageOptions options, int retryCounter = 0)
{
string requestKey = this.GetRequestKey(imageUrl, options);
RemoteImageRequest requestToStart =
this.imageRequests.GetOrAdd(
requestKey,
_ =>
new RemoteImageRequest(
() => this.resourceDownloader.DownloadImage(imageUrl, options),
result => this.DownloadComplete(requestKey, result),
imageData => this.imageCache.Put(requestKey, imageData),
retryCounter));
this.StartPendingDownloadsAsync();
return(requestToStart);
}