/// <summary>
/// Tries to the move to the next page in the document producer.
/// </summary>
/// <param name="token">The cancellation token.</param>
/// <returns>Whether the operation was successful.</returns>
private async Task <bool> MoveNextPageAsync(CancellationToken token)
{
token.ThrowIfCancellationRequested();
if (this.itemsLeftInCurrentPage != 0)
{
throw new InvalidOperationException("Tried to move onto the next page before finishing the first page.");
}
// We need to buffer pages if empty, since that how we know there are no more pages left.
await this.BufferMoreIfEmptyAsync(token);
if (this.bufferedPages.Count == 0)
{
return(false);
}
// Pull a FeedResponse using TryMonad (we could have buffered an exception).
TryMonad <DocumentFeedResponse <CosmosElement> > tryMonad = await this.bufferedPages.TakeAsync(token);
DocumentFeedResponse <CosmosElement> feedResponse = tryMonad.Match <DocumentFeedResponse <CosmosElement> >(
onSuccess: ((page) =>
{
return(page);
}),
onError: (exceptionDispatchInfo) =>
{
exceptionDispatchInfo.Throw();
return(null);
});
// Update the state.
this.PreviousContinuationToken = this.currentContinuationToken;
this.currentContinuationToken = feedResponse.ResponseContinuation;
this.currentPage = feedResponse.GetEnumerator();
this.IsAtBeginningOfPage = true;
this.itemsLeftInCurrentPage = feedResponse.Count;
// Prime the enumerator,
// so that current is pointing to the first document instead of one before.
if (this.MoveToFirstDocumentInPage())
{
this.IsAtBeginningOfPage = true;
return(true);
}
else
{
// We got an empty page
if (this.currentContinuationToken != null)
{
return(await this.MoveNextPageAsync(token));
}
return(false);
}
}
/// <summary>
/// Tries to the move to the next page in the document producer.
/// </summary>
/// <param name="token">The cancellation token.</param>
/// <returns>Whether the operation was successful.</returns>
private async Task <bool> MoveNextPageAsync(CancellationToken token)
{
token.ThrowIfCancellationRequested();
if (this.bufferedPages.Count == 0)
{
return(false);
}
if (this.itemsLeftInCurrentPage != 0)
{
throw new InvalidOperationException("Tried to move onto the next page before finishing the first page.");
}
TryMonad <DocumentFeedResponse <CosmosElement> > tryMonad = await this.bufferedPages.TakeAsync(token);
DocumentFeedResponse <CosmosElement> feedResponse = tryMonad.Match <DocumentFeedResponse <CosmosElement> >(
onSuccess: ((page) =>
{
return(page);
}),
onError: (exceptionDispatchInfo) =>
{
exceptionDispatchInfo.Throw();
return(null);
});
this.previousContinuationToken = this.currentContinuationToken;
this.currentContinuationToken = feedResponse.ResponseContinuation;
this.currentPage = feedResponse.GetEnumerator();
this.itemsLeftInCurrentPage = feedResponse.Count;
if (this.MoveNextDocumentWithinCurrentPage())
{
this.isAtBeginningOfPage = true;
return(true);
}
else
{
return(false);
}
}
/// <summary>
/// Buffers more documents in the producer.
/// </summary>
/// <param name="token">The cancellation token.</param>
/// <returns>A task to await on.</returns>
public async Task BufferMoreDocumentsAsync(CancellationToken token)
{
token.ThrowIfCancellationRequested();
try
{
await this.fetchSemaphore.WaitAsync();
if (!this.HasMoreBackendResults)
{
// Just NOP
return;
}
this.fetchSchedulingMetrics.Start();
this.fetchExecutionRangeAccumulator.BeginFetchRange();
int pageSize = (int)Math.Min(this.pageSize, (long)int.MaxValue);
using (DocumentServiceRequest request = this.createRequestFunc(this.PartitionKeyRange, this.backendContinuationToken, pageSize))
{
IDocumentClientRetryPolicy retryPolicy = this.createRetryPolicyFunc();
// Custom backoff and retry
while (true)
{
int retries = 0;
try
{
DocumentFeedResponse <CosmosElement> feedResponse = await this.executeRequestFunc(request, retryPolicy, token);
this.fetchExecutionRangeAccumulator.EndFetchRange(
this.PartitionKeyRange.Id,
feedResponse.ActivityId,
feedResponse.Count,
retries);
this.fetchSchedulingMetrics.Stop();
this.hasStartedFetching = true;
this.backendContinuationToken = feedResponse.ResponseContinuation;
this.activityId = Guid.Parse(feedResponse.ActivityId);
await this.bufferedPages.AddAsync(TryMonad <DocumentFeedResponse <CosmosElement> > .FromResult(feedResponse));
Interlocked.Add(ref this.bufferedItemCount, feedResponse.Count);
QueryMetrics queryMetrics = QueryMetrics.Zero;
if (feedResponse.ResponseHeaders[HttpConstants.HttpHeaders.QueryMetrics] != null)
{
queryMetrics = QueryMetrics.CreateFromDelimitedStringAndClientSideMetrics(
feedResponse.ResponseHeaders[HttpConstants.HttpHeaders.QueryMetrics],
new ClientSideMetrics(
retries,
feedResponse.RequestCharge,
this.fetchExecutionRangeAccumulator.GetExecutionRanges(),
new List <Tuple <string, SchedulingTimeSpan> >()));
}
if (!this.HasMoreBackendResults)
{
queryMetrics = QueryMetrics.CreateWithSchedulingMetrics(
queryMetrics,
new List <Tuple <string, SchedulingTimeSpan> >
{
new Tuple <string, SchedulingTimeSpan>(
this.PartitionKeyRange.Id,
this.fetchSchedulingMetrics.Elapsed)
});
}
this.produceAsyncCompleteCallback(
this,
feedResponse.Count,
feedResponse.RequestCharge,
queryMetrics,
feedResponse.ResponseLengthBytes,
token);
break;
}
catch (Exception exception)
{
// See if we need to retry or just throw
ShouldRetryResult shouldRetryResult = await retryPolicy.ShouldRetryAsync(exception, token);
if (!shouldRetryResult.ShouldRetry)
{
Exception exceptionToBuffer;
if (shouldRetryResult.ExceptionToThrow != null)
{
exceptionToBuffer = shouldRetryResult.ExceptionToThrow;
}
else
{
// Propagate original exception.
exceptionToBuffer = exception;
}
// Buffer the exception instead of throwing, since we don't want an unobserved exception.
await this.bufferedPages.AddAsync(TryMonad <DocumentFeedResponse <CosmosElement> > .FromException(exceptionToBuffer));
// null out the backend continuation token,
// so that people stop trying to buffer more on this producer.
this.hasStartedFetching = true;
this.backendContinuationToken = null;
break;
}
else
{
await Task.Delay(shouldRetryResult.BackoffTime);
retries++;
}
}
}
}
}
finally
{
this.fetchSchedulingMetrics.Stop();
this.fetchSemaphore.Release();
}
}
public void SetUp()
{
sut = new TryMonad();
}
