write to file sequentially using azure queue

Question

new to queues here.

I have many tasks in a queue where each of them consist in appending data to a file through a function app. I want to perform those tasks sequentially.

My understanding from the docs is that I need to set batchSize to 1 in host.json in order to get the messages processed sequentially:

{  
  "version": "2.0",  
  "extensions": {  
    "queues": {  
      "maxDequeueCount" : 3,  
      "batchSize": 1,  
      "newBatchThreshold": 1000,  
      "messageEncoding" :"none"  
    }  
      
  },  
  "extensionBundle": {  
    "id": "Microsoft.Azure.Functions.ExtensionBundle",  
    "version": "[2.*, 3.0.0)"  
  }  
}  

Is this the correct way of achieving sequential processing of the tasks?

Answer 1

Hi @javier
There is also the problem o parallelism and queue storage does not support fifo (first in first out)
This article has a very good explanation on how far you can go with storage queues:
https://laurakokkarinen.com/forcing-an-azure-function-to-process-queue-storage-messages-one-at-a-time/

if you need to guarantee sequential processing, you will be better with azure service bus using the convoy pattern:
https://learn.microsoft.com/en-us/azure/architecture/patterns/sequential-convoy

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Answer 2

@Bruno Lucas this is great. I am not looking for FIFO processing, just one-at-a-time processing your answer should work perfectly. thanks