Azure Function and queue

Question

I have a function:

    public async static Task Run([QueueTrigger("efs-api-call-last-datetime", Connection = "StorageConnectionString")]DateTime queueItem,
        [Queue("efs-api-call-last-datetime", Connection = "StorageConnectionString")]CloudQueue inputQueue,
        TraceWriter log)
    {

Then I have long process for processing message from queue. Problem is the message will be readded to queue after 30 seconds, while I process this message. I don't need to add this message and process it twice. I would like to have code like:

        try
        {
             // long operation
        }
        catch(Exception ex)
        {
            // something wrong. Readd this message in 1 minute
            await inputQueue.AddMessageAsync(new CloudQueueMessage(
                JsonConvert.SerializeObject(queueItem)),
                timeToLive: null,
                initialVisibilityDelay: TimeSpan.FromMinutes(1),
                options: null,
                operationContext: null
                );
        }

and prevent to readd it automatically. Any way to do it?

Answer 1

There are couple of things here.

1) When there are multiple queue messages waiting, the queue trigger retrieves a batch of messages and invokes function instances concurrently to process them. By default, the batch size is 16. But this is configurable in Host.json. You can set the batch size to 1 if you want to minimize the parallel execution. Microsoft document explains this.

2) As it is long running process so it seems your messages are not complete and the function might timeout and message are visible again. You should try to break down your function into smaller functions. Then you can use durable function which will chain the work you have to do.