Azure function app goes into sleep , manual intervention is required to wakeup

Question

Hi,

I have an azure function app v4 - in process with Blob trigger as you see below. This is hosted on app service with consumption plan. Time to time it goes into sleep - meaning it stops receiving the events from Blob until I manually wake it up.

To wake up - all that I need to do is navigate to the function app in portal. Then it starts processing the events. Appreciate any help to resolve this.

 [FunctionName("ArchiveFunction")]  
         public static async Task RunAsync([BlobTrigger("%BlobContainer%/{name}", Connection = "StorageConnection")] Stream myBlob, string name,  
             [CosmosDB(  
         databaseName: "PCArchive",  
         collectionName: "PCEvents",  
         ConnectionStringSetting = "CosmosDbConnectionString")]IAsyncCollector<dynamic> documentsOut, ILogger log,  
         [CosmosDB(  
         databaseName: "PCArchive",  
         collectionName: "Online_Event",  
         CreateIfNotExists =true,  
         ConnectionStringSetting = "CosmosDbConnectionString")]IAsyncCollector<dynamic> leaseSBOOut)  

         I have few other function app with isolated process, there's no problem with them.   

/Daniel

Answer 1

Function app running on consumption plan using the blob triggers rely on the Scale Controller to start up the app. The Scale Controller will poll the storage logs to determine if there are any changes/additions to the blobs. However, using the storage logs isn't 100% reliable.

Reference : https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-storage-blob-trigger?tabs=in-process%2Cextensionv5&pivots=programming-language-csharp#polling-and-latency

Answer 2

Does this help?

https://learn.microsoft.com/en-us/azure/azure-functions/functions-scale#cold-start-behavior

Answer 3

I have the same problem although with a Queue trigger.
My function app stops processing queue messages and only wakes up when I go to its blade in the portal.
Also on Consumption plan.
Is this normal behavior ?

Answer 4

We have an InProcess .NET 7 Isolated function(with Blob Trigger) running on Consumption plan that exhibited this same behavior. We had to upgrade our plan to "Function Premium" and then the issue went away.