How to call Azure Functions based on the Function Slots - azure

Question

I had multiple Azure Functions which are deployed in different Azure Function slots. The functions are called based on the CloudStorage QueueMessage as below.
// Get storage account
CloudStorageAccount storageAccount = CloudStorageAccount.Parse(Microsoft.Azure.CloudConfigurationManager.GetSetting("StorageConnectionString"));
// Next, create a queue client
CloudQueueClient queueClient = storageAccount.CreateCloudQueueClient();
// Then retrieve a reference to a queue – here’s where you give your queue a name
CloudQueue queue = queueClient.GetQueueReference(queueName);
// Create the queue if it doesn’t already exist
queue.CreateIfNotExists();
// Penultimate step – create a message and add it to the queue.
CloudQueueMessage message = new CloudQueueMessage(bordereauxId.ToString());
// Finally, add your message to the queue
queue.AddMessage(message);
// Fetch the queue attributes.
queue.FetchAttributes();
Is there any way to queue the message based on the Slots. For example, if the user is using development site then the function queue should call the function that belongs to Devlopment Slot using the same storage account.

Answer 1

As #MurrayFoxcroft suggested, you should use per-slot App Settings to configure your storage accounts per App Slot.
To add, you should replace all the code you are quoting with an Storage Queue output binding:
{
"type": "queue",
"direction": "out",
"name": "$return",
"queueName": "outqueue",
"connection": "StorageConnectionString",
}
Then the function will just return the queue message (you can use out params too).
StorageConnectionString should be an app setting pinned to App Slot.

Answer 2

You can determine if your function is running in a slot by using the following:
var slot = System.Environment.GetEnvironmentVariable("APPSETTING_WEBSITE_SLOT_NAME", EnvironmentVariableTarget.Process);
You can then use the result to direct your code down the correct path.
However, where possible, I'd avoid coding in logic to handle different scenarios based on slot. Try to drive your logic from configuration where possible. For example, in your AppSettings you can configure sticky settings (Slot Settings) to provide configuration per slot.
When running locally you should be using the Azure Functions Core Tools for debugging. See this link. Put your sample app settings in localsettings.json to test your function. Change them appropriately or use multiple files to simulate your slots.

Answer 3

I got the solution by making the queue name based on the slots
So in my console application now the queue name is based on the slot I want to call and added in the config file.
// Then retrieve a reference to a queue – here’s where you give your queue a name
CloudQueue queue = queueClient.GetQueueReference(queueName + "_" + slotname);
And the queue name in the function is defined based on the slot application settings
Hence in the Azure function method the queue name will be defined as below
public static void Run([QueueTrigger("%slot_queue_name%", Connection = "AzureWebJobsStorage")]string myQueueItem)
Where the "slot_queue_name" will be defined in the Azure Function slot Application settings.