azure-webjobs Azure Webjobs SDK Scaling
Example
Azure Webjobs run on an Azure App Service. If we scale our App Service horizontally (add new instances), each instance will have its own JobHost.
Note that this only applies to WebJobs running in Continuous mode. On-demand and scheduled WebJobs are not affected by horizontal scaling, they always run a single instance.
If you have a continuous WebJob processing queue messages, and you scale the App Service Plan to 3 instances, you will have 3 instances of the WebJob running.
There might be WebJobs that you want to run in a single instance, because you might need to ensure that exactly one processing pipeline exists. For those WebJobs, you can add the Singleton attribute.
[Singleton]
public static void SingletonQueueProcessing([QueueTrigger("my_queue")] MyPOCOClass aMessage)
{
//...
}
This is achieved by Azure Blob Leases for distributed locking.
