Per this documentation, I am using the Azure Function consumption plan and am trying to limit the parallelism of one of the queue-triggered functions so that only one instance runs at a time:
{
"queues": {
"batchSize": 1
}
}
The queue is part of a Microsoft Storage Account, and isn't a service bus.
However, my problem is that the function is still being run in parallel if there are multiple items on the queue at once. I read in the fine print of the documentation above:
If you want to avoid parallel execution for messages received on one queue, you can set batchSize to 1. However, this setting eliminates concurrency only so long as your function app runs on a single virtual machine (VM). If the function app scales out to multiple VMs, each VM could run one instance of each queue-triggered function.
Since I am using a consumption plan, how do I know if the function app is running on a single VM or on multiple? How can I successfully limit this function's batch size to one?
In consumption plan, a single function app only scales up to a maximum of 200 instances. A single instance may process more than one message or request at a time though, so there isn't a set limit on number of concurrent executions.
Also, when you're using a Consumption plan, instances of the Azure Functions host are dynamically added and removed based on the number of incoming events.
As you want to limit the parallelism of one of the queue-triggered functions, so I suggest that you could use Azure App Service Plan to achieve it.
For more details, you could refer to this article.