public async ValueTask <bool> MoveNextAsync()
{
this.cancellationToken.ThrowIfCancellationRequested();
if (!await this.crossPartitionEnumerator.MoveNextAsync())
{
this.Current = default;
return(false);
}
TryCatch <CrossPartitionPage <ReadFeedPage, ReadFeedState> > monadicCrossPartitionPage = this.crossPartitionEnumerator.Current;
if (monadicCrossPartitionPage.Failed)
{
this.Current = TryCatch <ReadFeedPage> .FromException(monadicCrossPartitionPage.Exception);
return(true);
}
CrossPartitionPage <ReadFeedPage, ReadFeedState> crossPartitionPage = monadicCrossPartitionPage.Result;
ReadFeedPage backendPage = crossPartitionPage.Page;
CrossPartitionState <ReadFeedState> crossPartitionState = crossPartitionPage.State;
ReadFeedState state;
if (crossPartitionState != null)
{
IReadOnlyList <(FeedRangeInternal, ReadFeedState)> rangesAndStates = crossPartitionState.Value;
List <CosmosElement> changeFeedContinuationTokens = new List <CosmosElement>();
foreach ((FeedRangeInternal range, ReadFeedState readFeedState) in rangesAndStates)
{
this.cancellationToken.ThrowIfCancellationRequested();
ReadFeedContinuationToken readFeedContinuationToken = new ReadFeedContinuationToken(
range,
readFeedState);
CosmosElement cosmosElementChangeFeedContinuationToken = ReadFeedContinuationToken.ToCosmosElement(readFeedContinuationToken);
changeFeedContinuationTokens.Add(cosmosElementChangeFeedContinuationToken);
}
CosmosArray cosmosElementTokens = CosmosArray.Create(changeFeedContinuationTokens);
state = new ReadFeedState(cosmosElementTokens);
}
else
{
state = null;
}
ReadFeedPage compositePage = new ReadFeedPage(backendPage.Content, backendPage.RequestCharge, backendPage.ActivityId, backendPage.Diagnostics, state);
this.Current = TryCatch <ReadFeedPage> .FromResult(compositePage);
return(true);
}
public async ValueTask <bool> MoveNextAsync()
{
this.cancellationToken.ThrowIfCancellationRequested();
if (this.bufferedException.HasValue)
{
this.Current = this.bufferedException.Value;
this.bufferedException = null;
return(true);
}
if (!await this.crossPartitionEnumerator.MoveNextAsync())
{
throw new InvalidOperationException("ChangeFeed should always have a next page.");
}
TryCatch <CrossPartitionPage <ChangeFeedPage, ChangeFeedState> > monadicCrossPartitionPage = this.crossPartitionEnumerator.Current;
if (monadicCrossPartitionPage.Failed)
{
this.Current = TryCatch <ChangeFeedPage> .FromException(monadicCrossPartitionPage.Exception);
return(true);
}
CrossPartitionPage <ChangeFeedPage, ChangeFeedState> crossPartitionPage = monadicCrossPartitionPage.Result;
ChangeFeedPage backendPage = crossPartitionPage.Page;
if (backendPage is ChangeFeedNotModifiedPage)
{
// Keep draining the cross partition enumerator until
// We get a non 304 page or we loop back to the same range or run into an exception
FeedRangeInternal originalRange = this.crossPartitionEnumerator.CurrentRange;
double totalRequestCharge = backendPage.RequestCharge;
do
{
if (!await this.crossPartitionEnumerator.MoveNextAsync())
{
throw new InvalidOperationException("ChangeFeed should always have a next page.");
}
monadicCrossPartitionPage = this.crossPartitionEnumerator.Current;
if (monadicCrossPartitionPage.Failed)
{
// Buffer the exception, since we need to return the request charge so far.
this.bufferedException = TryCatch <ChangeFeedPage> .FromException(monadicCrossPartitionPage.Exception);
}
else
{
crossPartitionPage = monadicCrossPartitionPage.Result;
backendPage = crossPartitionPage.Page;
totalRequestCharge += backendPage.RequestCharge;
}
}while (!(backendPage is ChangeFeedSuccessPage ||
this.crossPartitionEnumerator.CurrentRange.Equals(originalRange) ||
this.bufferedException.HasValue));
// Create a page with the aggregated request charge
if (backendPage is ChangeFeedSuccessPage changeFeedSuccessPage)
{
backendPage = new ChangeFeedSuccessPage(
changeFeedSuccessPage.Content,
totalRequestCharge,
changeFeedSuccessPage.ActivityId,
changeFeedSuccessPage.State);
}
else
{
backendPage = new ChangeFeedNotModifiedPage(
totalRequestCharge,
backendPage.ActivityId,
backendPage.State);
}
}
CrossPartitionState <ChangeFeedState> crossPartitionState = crossPartitionPage.State;
List <CosmosElement> changeFeedContinuationTokens = new List <CosmosElement>();
foreach ((FeedRangeInternal range, ChangeFeedState state)rangeAndState in crossPartitionState.Value)
{
ChangeFeedContinuationToken changeFeedContinuationToken = new ChangeFeedContinuationToken(
rangeAndState.range,
rangeAndState.state);
CosmosElement cosmosElementChangeFeedContinuationToken = ChangeFeedContinuationToken.ToCosmosElement(changeFeedContinuationToken);
changeFeedContinuationTokens.Add(cosmosElementChangeFeedContinuationToken);
}
CosmosArray cosmosElementTokens = CosmosArray.Create(changeFeedContinuationTokens);
ChangeFeedState state = ChangeFeedState.Continuation(cosmosElementTokens);
ChangeFeedPage compositePage;
if (backendPage is ChangeFeedSuccessPage successPage)
{
compositePage = new ChangeFeedSuccessPage(
successPage.Content,
successPage.RequestCharge,
successPage.ActivityId,
state);
}
else
{
compositePage = new ChangeFeedNotModifiedPage(
backendPage.RequestCharge,
backendPage.ActivityId,
state);
}
this.Current = TryCatch <ChangeFeedPage> .FromResult(compositePage);
return(true);
}
// In order to maintain the continuation token for the user we must drain with a few constraints
// 1) We fully drain from the left most partition before moving on to the next partition
// 2) We drain only full pages from the document producer so we aren't left with a partial page
// otherwise we would need to add to the continuation token how many items to skip over on that page.
public async ValueTask <bool> MoveNextAsync()
{
this.cancellationToken.ThrowIfCancellationRequested();
if (!await this.crossPartitionRangePageAsyncEnumerator.MoveNextAsync())
{
this.Current = default;
return(false);
}
TryCatch <CrossPartitionPage <QueryPage, QueryState> > currentCrossPartitionPage = this.crossPartitionRangePageAsyncEnumerator.Current;
if (currentCrossPartitionPage.Failed)
{
this.Current = TryCatch <QueryPage> .FromException(currentCrossPartitionPage.Exception);
return(true);
}
CrossPartitionPage <QueryPage, QueryState> crossPartitionPageResult = currentCrossPartitionPage.Result;
QueryPage backendQueryPage = crossPartitionPageResult.Page;
CrossPartitionState <QueryState> crossPartitionState = crossPartitionPageResult.State;
QueryState queryState;
if (crossPartitionState == null)
{
queryState = null;
}
else
{
// Left most and any non null continuations
List <(PartitionKeyRange, QueryState)> rangesAndStates = crossPartitionState.Value.OrderBy(tuple => tuple.Item1, PartitionKeyRangeComparer.Singleton).ToList();
List <ParallelContinuationToken> activeParallelContinuationTokens = new List <ParallelContinuationToken>();
for (int i = 0; i < rangesAndStates.Count; i++)
{
this.cancellationToken.ThrowIfCancellationRequested();
(PartitionKeyRange range, QueryState state) = rangesAndStates[i];
if ((i == 0) || (state != null))
{
ParallelContinuationToken parallelContinuationToken = new ParallelContinuationToken(
token: state != null ? ((CosmosString)state.Value).Value : null,
range: range.ToRange());
activeParallelContinuationTokens.Add(parallelContinuationToken);
}
}
IEnumerable <CosmosElement> cosmosElementContinuationTokens = activeParallelContinuationTokens
.Select(token => ParallelContinuationToken.ToCosmosElement(token));
CosmosArray cosmosElementParallelContinuationTokens = CosmosArray.Create(cosmosElementContinuationTokens);
queryState = new QueryState(cosmosElementParallelContinuationTokens);
}
QueryPage crossPartitionQueryPage = new QueryPage(
backendQueryPage.Documents,
backendQueryPage.RequestCharge,
backendQueryPage.ActivityId,
backendQueryPage.ResponseLengthInBytes,
backendQueryPage.CosmosQueryExecutionInfo,
backendQueryPage.DisallowContinuationTokenMessage,
queryState);
this.Current = TryCatch <QueryPage> .FromResult(crossPartitionQueryPage);
return(true);
}
