public async Task <FunctionResult> ExecuteAsync(IStorageQueueMessage value, CancellationToken cancellationToken)
{
BlobTriggerMessage message = JsonConvert.DeserializeObject <BlobTriggerMessage>(value.AsString, JsonSerialization.Settings);
if (message == null)
{
throw new InvalidOperationException("Invalid blob trigger message.");
}
string functionId = message.FunctionId;
if (functionId == null)
{
throw new InvalidOperationException("Invalid function ID.");
}
// Ensure that the function ID is still valid. Otherwise, ignore this message.
FunctionResult successResult = new FunctionResult(true);
BlobQueueRegistration registration;
if (!_registrations.TryGetValue(functionId, out registration))
{
return(successResult);
}
IStorageBlobContainer container = registration.BlobClient.GetContainerReference(message.ContainerName);
string blobName = message.BlobName;
IStorageBlob blob;
switch (message.BlobType)
{
case StorageBlobType.PageBlob:
blob = container.GetPageBlobReference(blobName);
break;
case StorageBlobType.BlockBlob:
default:
blob = container.GetBlockBlobReference(blobName);
break;
}
// Ensure the blob still exists with the same ETag.
string possibleETag = await _eTagReader.GetETagAsync(blob, cancellationToken);
if (possibleETag == null)
{
// If the blob no longer exists, just ignore this message.
return(successResult);
}
// If the blob still exists but the ETag is different, delete the message but do a fast path notification.
if (!String.Equals(message.ETag, possibleETag, StringComparison.Ordinal))
{
_blobWrittenWatcher.Notify(blob);
return(successResult);
}
//// If the blob still exists and its ETag is still valid, execute.
//// Note: it's possible the blob could change/be deleted between now and when the function executes.
Guid?parentId = await _causalityReader.GetWriterAsync(blob, cancellationToken);
TriggeredFunctionData input = new TriggeredFunctionData
{
ParentId = parentId,
TriggerValue = blob
};
return(await registration.Executor.TryExecuteAsync(input, cancellationToken));
}
public async Task <FunctionResult> ExecuteAsync(IStorageBlob value, CancellationToken cancellationToken)
{
// Avoid unnecessary network calls for non-matches. First, check to see if the blob matches this trigger.
IReadOnlyDictionary <string, object> bindingData = _input.CreateBindingData(value.ToBlobPath());
if (bindingData == null)
{
// Blob is not a match for this trigger.
return(new FunctionResult(true));
}
// Next, check to see if the blob currently exists (and, if so, what the current ETag is).
string possibleETag = await _eTagReader.GetETagAsync(value, cancellationToken);
if (possibleETag == null)
{
// If the blob doesn't exist and have an ETag, don't trigger on it.
return(new FunctionResult(true));
}
IStorageBlockBlob receiptBlob = _receiptManager.CreateReference(_hostId, _functionId, value.Container.Name,
value.Name, possibleETag);
// Check for the completed receipt. If it's already there, noop.
BlobReceipt unleasedReceipt = await _receiptManager.TryReadAsync(receiptBlob, cancellationToken);
if (unleasedReceipt != null && unleasedReceipt.IsCompleted)
{
return(new FunctionResult(true));
}
else if (unleasedReceipt == null)
{
// Try to create (if not exists) an incomplete receipt.
if (!await _receiptManager.TryCreateAsync(receiptBlob, cancellationToken))
{
// Someone else just created the receipt; wait to try to trigger until later.
// Alternatively, we could just ignore the return result and see who wins the race to acquire the
// lease.
return(new FunctionResult(false));
}
}
string leaseId = await _receiptManager.TryAcquireLeaseAsync(receiptBlob, cancellationToken);
if (leaseId == null)
{
// If someone else owns the lease and just took over this receipt or deleted it;
// wait to try to trigger until later.
return(new FunctionResult(false));
}
ExceptionDispatchInfo exceptionInfo;
try
{
// Check again for the completed receipt. If it's already there, noop.
BlobReceipt receipt = await _receiptManager.TryReadAsync(receiptBlob, cancellationToken);
Debug.Assert(receipt != null); // We have a (30 second) lease on the blob; it should never disappear on us.
if (receipt.IsCompleted)
{
await _receiptManager.ReleaseLeaseAsync(receiptBlob, leaseId, cancellationToken);
return(new FunctionResult(true));
}
// We've successfully acquired a lease to enqueue the message for this blob trigger. Enqueue the message,
// complete the receipt and release the lease.
// Enqueue a message: function ID + blob path + ETag
BlobTriggerMessage message = new BlobTriggerMessage
{
FunctionId = _functionId,
BlobType = value.BlobType,
ContainerName = value.Container.Name,
BlobName = value.Name,
ETag = possibleETag
};
await _queueWriter.EnqueueAsync(message, cancellationToken);
// Complete the receipt & release the lease
await _receiptManager.MarkCompletedAsync(receiptBlob, leaseId, cancellationToken);
await _receiptManager.ReleaseLeaseAsync(receiptBlob, leaseId, cancellationToken);
return(new FunctionResult(true));
}
catch (Exception exception)
{
exceptionInfo = ExceptionDispatchInfo.Capture(exception);
}
Debug.Assert(exceptionInfo != null);
await _receiptManager.ReleaseLeaseAsync(receiptBlob, leaseId, cancellationToken);
exceptionInfo.Throw();
FunctionResult result = new FunctionResult(exceptionInfo.SourceException);
return(result); // Keep the compiler happy; we'll never get here.
}