Verifying Concurrency in Azure Functions Blob Triggers During Local Testing

Question

Methods for verifying concurrency within Azure Functions Blob Triggers while testing locally are needed. Dynamic concurrency has been enabled in host.json, but clarification is sought on how to test this locally.

Reference: Dynamic Concurrency in Azure Functions

Previous Question link: Blob Trigger Azure Function Using Same Queue Name

Answer 1

Hello @Keerthana, D

To test the dynamic concurrency feature of Azure Functions Blob Triggers locally, you can use the Azure Storage Emulator. The Azure Storage Emulator provides a local environment that emulates the Azure Blob, Queue, and Table services for development purposes. To use the Azure Storage Emulator with Azure Functions, you need to configure your function app to use the emulator. You can do this by setting the AzureWebJobsStorage app setting to the connection string for the emulator. Here's an example of how to set the AzureWebJobsStorage app setting to use the Azure Storage Emulator:

{
	"IsEncrypted": false,
	"Values": 
	{ 
		"AzureWebJobsStorage": "UseDevelopmentStorage=true", 
		"FUNCTIONS_WORKER_RUNTIME": "dotnet"
	}

}

Additionally, if you are using VSCode, download and setup Azurite.

Use the Azurite emulator for local Azure Storage development

Once you have configured your function app to use the Azure Storage Emulator, you can test the dynamic concurrency feature by running multiple instances of your function app locally and monitoring the concurrency levels in the logs. To monitor the concurrency levels in the logs, you can look for logs with the Host.Concurrency log category in the traces table.

These logs will show you when various throttles are enabled, and whenever concurrency is adjusted up or down for each function.

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