/// <summary>
/// Updates the checkpoint using the given information for the associated partition and consumer group in the storage blob service.
/// </summary>
///
/// <param name="checkpoint">The checkpoint containing the information to be stored.</param>
///
/// <returns>A task to be resolved on when the operation has completed.</returns>
///
public override async Task UpdateCheckpointAsync(Checkpoint checkpoint)
{
var blobName = $"{ checkpoint.FullyQualifiedNamespace }/{ checkpoint.EventHubName }/{ checkpoint.ConsumerGroup }/{ checkpoint.PartitionId }";
BlobClient blobClient = _containerClient.GetBlobClient(blobName);
BlobProperties currentBlob;
try
{
currentBlob = (await blobClient.GetPropertiesAsync().ConfigureAwait(false)).Value;
}
catch (StorageRequestFailedException ex) when(ex.ErrorCode == BlobErrorCode.BlobNotFound)
{
Log($"Checkpoint with partition id = '{ checkpoint.PartitionId }' could not be updated because no associated ownership was found.");
return;
}
// In case this key does not exist, ownerIdentifier is set to null. The OwnerIdentifier in Checkpoint cannot
// be null as well, so we won't be able to update the associated ownership.
currentBlob.Metadata.TryGetValue(BlobMetadataKey.OwnerIdentifier, out var ownerIdentifier);
if (ownerIdentifier == checkpoint.OwnerIdentifier)
{
var metadata = new Dictionary <string, string>()
{
{ BlobMetadataKey.OwnerIdentifier, checkpoint.OwnerIdentifier },
{ BlobMetadataKey.Offset, checkpoint.Offset.ToString() },
{ BlobMetadataKey.SequenceNumber, checkpoint.SequenceNumber.ToString() }
};
var accessConditions = new BlobAccessConditions
{
HttpAccessConditions = new HttpAccessConditions {
IfMatch = currentBlob.ETag
}
};
try
{
await blobClient.SetMetadataAsync(metadata, accessConditions).ConfigureAwait(false);
Log($"Checkpoint with partition id = '{ checkpoint.PartitionId }' updated.");
}
catch (StorageRequestFailedException ex) when(ex.ErrorCode == BlobErrorCode.ConditionNotMet)
{
Log($"Checkpoint with partition id = '{ checkpoint.PartitionId }' could not be updated because eTag has changed.");
}
}
else
{
Log($"Checkpoint with partition id = '{ checkpoint.PartitionId }' could not be updated because owner has changed.");
}
}
/// <summary>
/// Attempts to claim ownership of partitions for processing.
/// </summary>
///
/// <param name="partitionOwnership">An enumerable containing all the ownership to claim.</param>
///
/// <returns>An enumerable containing the successfully claimed ownership.</returns>
///
public override async Task <IEnumerable <PartitionOwnership> > ClaimOwnershipAsync(IEnumerable <PartitionOwnership> partitionOwnership)
{
var claimedOwnership = new List <PartitionOwnership>();
var metadata = new Dictionary <string, string>();
Response <BlobContentInfo> contentInfoResponse;
Response <BlobInfo> infoResponse;
foreach (var ownership in partitionOwnership)
{
metadata[BlobMetadataKey.OwnerIdentifier] = ownership.OwnerIdentifier;
metadata[BlobMetadataKey.Offset] = ownership.Offset?.ToString() ?? String.Empty;
metadata[BlobMetadataKey.SequenceNumber] = ownership.SequenceNumber?.ToString() ?? String.Empty;
var blobAccessConditions = new BlobAccessConditions();
var blobName = $"{ ownership.EventHubName }/{ ownership.ConsumerGroup }/{ ownership.PartitionId }";
var blobClient = ContainerClient.GetBlobClient(blobName);
try
{
// Even though documentation states otherwise, we cannot use UploadAsync when the blob already exists in
// the current storage SDK. For this reason, we are using the specified ETag as an indication of what
// method to use.
if (ownership.ETag == null)
{
blobAccessConditions.HttpAccessConditions = new HttpAccessConditions {
IfNoneMatch = new ETag("*")
};
MemoryStream blobContent = null;
try
{
blobContent = new MemoryStream(new byte[0]);
contentInfoResponse = await blobClient.UploadAsync(blobContent, metadata : metadata, blobAccessConditions : blobAccessConditions).ConfigureAwait(false);
}
catch (StorageRequestFailedException ex) when(ex.ErrorCode == BlobErrorCode.BlobAlreadyExists)
{
// A blob could have just been created by another Event Processor that claimed ownership of this
// partition. In this case, there's no point in retrying because we don't have the correct ETag.
Log($"Ownership with partition id = '{ ownership.PartitionId }' is not claimable.");
continue;
}
finally
{
blobContent?.Dispose();
}
ownership.LastModifiedTime = contentInfoResponse.Value.LastModified;
ownership.ETag = contentInfoResponse.Value.ETag.ToString();
}
else
{
blobAccessConditions.HttpAccessConditions = new HttpAccessConditions {
IfMatch = new ETag(ownership.ETag)
};
try
{
infoResponse = await blobClient.SetMetadataAsync(metadata, blobAccessConditions).ConfigureAwait(false);
}
catch (StorageRequestFailedException ex) when(ex.ErrorCode == BlobErrorCode.BlobNotFound)
{
// No ownership was found, which means the ETag should have been set to null in order to
// claim this ownership. For this reason, we consider it a failure and don't try again.
Log($"Ownership with partition id = '{ ownership.PartitionId }' is not claimable.");
continue;
}
ownership.LastModifiedTime = infoResponse.Value.LastModified;
ownership.ETag = infoResponse.Value.ETag.ToString();
}
// Small workaround to retrieve the eTag. The current storage SDK returns it enclosed in
// double quotes ('"ETAG_VALUE"' instead of 'ETAG_VALUE').
var match = DoubleQuotesExpression.Match(ownership.ETag);
if (match.Success)
{
ownership.ETag = match.Groups[1].ToString();
}
claimedOwnership.Add(ownership);
Log($"Ownership with partition id = '{ ownership.PartitionId }' claimed.");
}
catch (StorageRequestFailedException ex) when(ex.ErrorCode == BlobErrorCode.ConditionNotMet)
{
Log($"Ownership with partition id = '{ ownership.PartitionId }' is not claimable.");
}
}
return(claimedOwnership);
}