public async Task <IListener> CreateAsync(CancellationToken cancellationToken)
{
// Note that these clients are intentionally for the storage account rather than for the dashboard account.
// We use the storage, not dashboard, account for the blob receipt container and blob trigger queues.
IStorageQueueClient primaryQueueClient = _hostAccount.CreateQueueClient();
IStorageBlobClient primaryBlobClient = _hostAccount.CreateBlobClient();
// Important: We're using the storage account of the function target here, which is the account that the
// function the listener is for is targeting. This is the account that will be used
// to read the trigger blob.
IStorageBlobClient targetBlobClient = _dataAccount.CreateBlobClient();
IStorageQueueClient targetQueueClient = _dataAccount.CreateQueueClient();
string hostId = await _hostIdProvider.GetHostIdAsync(cancellationToken);
string hostBlobTriggerQueueName = HostQueueNames.GetHostBlobTriggerQueueName(hostId);
IStorageQueue hostBlobTriggerQueue = primaryQueueClient.GetQueueReference(hostBlobTriggerQueueName);
SharedQueueWatcher sharedQueueWatcher = _sharedContextProvider.GetOrCreateInstance <SharedQueueWatcher>(
new SharedQueueWatcherFactory(_messageEnqueuedWatcherSetter));
SharedBlobListener sharedBlobListener = _sharedContextProvider.GetOrCreateInstance <SharedBlobListener>(
new SharedBlobListenerFactory(hostId, _hostAccount, _exceptionHandler, _blobWrittenWatcherSetter));
// Register the blob container we wish to monitor with the shared blob listener.
await RegisterWithSharedBlobListenerAsync(hostId, sharedBlobListener, primaryBlobClient,
hostBlobTriggerQueue, sharedQueueWatcher, cancellationToken);
// Create a "bridge" listener that will monitor the blob
// notification queue and dispatch to the target job function.
SharedBlobQueueListener sharedBlobQueueListener = _sharedContextProvider.GetOrCreateInstance <SharedBlobQueueListener>(
new SharedBlobQueueListenerFactory(_hostAccount, sharedQueueWatcher, hostBlobTriggerQueue,
_queueConfiguration, _exceptionHandler, _trace, _loggerFactory, sharedBlobListener.BlobWritterWatcher));
var queueListener = new BlobListener(sharedBlobQueueListener);
// determine which client to use for the poison queue
// by default this should target the same storage account
// as the blob container we're monitoring
var poisonQueueClient = targetQueueClient;
if (_dataAccount.Type != StorageAccountType.GeneralPurpose ||
_blobsConfiguration.CentralizedPoisonQueue)
{
// use the primary storage account if the centralize flag is true,
// or if the target storage account doesn't support queues
poisonQueueClient = primaryQueueClient;
}
// Register our function with the shared blob queue listener
RegisterWithSharedBlobQueueListenerAsync(sharedBlobQueueListener, targetBlobClient, poisonQueueClient);
// check a flag in the shared context to see if we've created the singleton
// shared blob listener in this host instance
object singletonListenerCreated = false;
if (!_sharedContextProvider.TryGetValue(SingletonBlobListenerScopeId, out singletonListenerCreated))
{
// Create a singleton shared blob listener, since we only
// want a single instance of the blob poll/scan logic to be running
// across host instances
var singletonBlobListener = _singletonManager.CreateHostSingletonListener(
new BlobListener(sharedBlobListener), SingletonBlobListenerScopeId);
_sharedContextProvider.SetValue(SingletonBlobListenerScopeId, true);
return(new CompositeListener(singletonBlobListener, queueListener));
}
else
{
// We've already created the singleton blob listener
// so just return our queue listener. Note that while we want the
// blob scan to be singleton, the shared queue listener needs to run
// on ALL instances so load can be scaled out
return(queueListener);
}
}