How to set Continuous WebJob as Singleton?

Question

I've seen some guidance around using settings.job to set the WebJob as singleton but it's not working - in the console, I see:

 WebJob singleton setting is False

How can I go about preventing scale-outs from running multiple instances of my WebJob?

Answer 1

As far as I know, to set a continuous job as singleton, we could create a file called settings.job with the content: { "is_singleton": true } and put it at the root of the WebJob directory. And we could get continuous job settings to make sure whether it is singleton.

GET /api/continuouswebjobs/{job name}/settings

in the console I see: WebJob singleton setting is False

Please use Kudu tool to check whether the settings.job is existing at the root of the WebJob directory and the actual value of is_singleton property.

Answer 2

If you can use the WebJobs SDK, I prefer to use the Singleton attribute.

How to use the Azure WebJobs SDK for event-driven background processing - Singleton attribute

[Singleton]
public static async Task ProcessImage([BlobTrigger("images")] Stream image)
{
     // Process the image.
}

If you have something like a ServiceBus trigger you should use [Singleton(Mode = SingletonMode.Listener)] in combination with the other host settings.