private async Task AdvanceSegmentIfNecessary(
bool async,
CancellationToken cancellationToken)
{
// If the current segment has more Events, we don't need to do anything.
if (_currentSegment.HasNext())
{
return;
}
// If the current segment is completed, remove it
if (_segments.Count > 0)
{
_currentSegment = await _segmentFactory.BuildSegment(
async,
_segments.Dequeue()).ConfigureAwait(false);
}
// If _segments is empty, refill it
else if (_segments.Count == 0 && _years.Count > 0)
{
string yearPath = _years.Dequeue();
// Get Segments for first year
_segments = await BlobChangeFeedExtensions.GetSegmentsInYearInternal(
containerClient : _containerClient,
yearPath : yearPath,
startTime : _startTime,
endTime : _endTime,
async : async,
cancellationToken : cancellationToken)
.ConfigureAwait(false);
if (_segments.Count > 0)
{
_currentSegment = await _segmentFactory.BuildSegment(
async,
_segments.Dequeue())
.ConfigureAwait(false);
}
}
}
public async Task <ChangeFeed> BuildChangeFeed(
DateTimeOffset?startTime,
DateTimeOffset?endTime,
string continuation,
bool async,
CancellationToken cancellationToken)
{
DateTimeOffset lastConsumable;
Queue <string> years = new Queue <string>();
Queue <string> segments = new Queue <string>();
ChangeFeedCursor cursor = null;
// Create cursor
if (continuation != null)
{
cursor = JsonSerializer.Deserialize <ChangeFeedCursor>(continuation);
ValidateCursor(_containerClient, cursor);
startTime = cursor.CurrentSegmentCursor.SegmentTime;
endTime = cursor.EndTime;
}
// Round start and end time if we are not using the cursor.
else
{
startTime = startTime.RoundDownToNearestHour();
endTime = endTime.RoundUpToNearestHour();
}
// Check if Change Feed has been abled for this account.
bool changeFeedContainerExists;
if (async)
{
changeFeedContainerExists = await _containerClient.ExistsAsync(cancellationToken : cancellationToken).ConfigureAwait(false);
}
else
{
changeFeedContainerExists = _containerClient.Exists(cancellationToken: cancellationToken);
}
if (!changeFeedContainerExists)
{
throw new ArgumentException("Change Feed hasn't been enabled on this account, or is currently being enabled.");
}
// Get last consumable
BlobClient blobClient = _containerClient.GetBlobClient(Constants.ChangeFeed.MetaSegmentsPath);
BlobDownloadInfo blobDownloadInfo;
if (async)
{
blobDownloadInfo = await blobClient.DownloadAsync(cancellationToken : cancellationToken).ConfigureAwait(false);
}
else
{
blobDownloadInfo = blobClient.Download(cancellationToken: cancellationToken);
}
JsonDocument jsonMetaSegment;
if (async)
{
jsonMetaSegment = await JsonDocument.ParseAsync(
blobDownloadInfo.Content,
cancellationToken : cancellationToken
).ConfigureAwait(false);
}
else
{
jsonMetaSegment = JsonDocument.Parse(blobDownloadInfo.Content);
}
lastConsumable = jsonMetaSegment.RootElement.GetProperty("lastConsumable").GetDateTimeOffset();
// Get year paths
years = await GetYearPathsInternal(
async,
cancellationToken).ConfigureAwait(false);
// Dequeue any years that occur before start time
if (startTime.HasValue)
{
while (years.Count > 0 &&
BlobChangeFeedExtensions.ToDateTimeOffset(years.Peek()) < startTime.RoundDownToNearestYear())
{
years.Dequeue();
}
}
// There are no years.
if (years.Count == 0)
{
return(ChangeFeed.Empty());
}
while (segments.Count == 0 && years.Count > 0)
{
// Get Segments for year
segments = await BlobChangeFeedExtensions.GetSegmentsInYearInternal(
containerClient : _containerClient,
yearPath : years.Dequeue(),
startTime : startTime,
endTime : BlobChangeFeedExtensions.MinDateTime(lastConsumable, endTime),
async : async,
cancellationToken : cancellationToken)
.ConfigureAwait(false);
}
// We were on the last year, and there were no more segments.
if (segments.Count == 0)
{
return(ChangeFeed.Empty());
}
Segment currentSegment = await _segmentFactory.BuildSegment(
async,
segments.Dequeue(),
cursor?.CurrentSegmentCursor)
.ConfigureAwait(false);
return(new ChangeFeed(
_containerClient,
_segmentFactory,
years,
segments,
currentSegment,
lastConsumable,
startTime,
endTime));
}