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); } }