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Quickstart: Running the Blob Source and Sink blocks with Managed ID

In this article you learn how to:

  • Create a blob storage account and container
  • Authenticate to the blob storage account from within GNU Radio
  • Simulate a signal in GNU Radio which then gets stored as a blob
  • Pull down the previously stored signal from blob storage and feed it through a GNU Radio flowgraph

The steps in this article will work for applications running on Azure resources that support managed identities.

Prerequisites

  • You must run the Key Vault example on a virtual machine in Azure to take advantage of managed identities. Follow these instructions to confirm your virtual machine is configured properly to use a managed identity.

  • Use the Bash environment in Azure Cloud Shell. For more information, see Azure Cloud Shell Quickstart - Bash

  • If you prefer to run CLI reference commands locally, install the Azure CLI. If you are running on Windows or macOS, consider running Azure CLI in a Docker container. For more information, see How to run the Azure CLI in a Docker container.

    • If you're using a local installation, sign in to the Azure CLI by using the az login command. To finish the authentication process, follow the steps displayed in your terminal. For additional sign-in options, see Sign in with the Azure CLI.

    • When you're prompted, install Azure CLI extensions on first use. For more information about extensions, see Use extensions with the Azure CLI.

    • Run az version to find the version and dependent libraries that are installed. To upgrade to the latest version, run az upgrade.

  • This article requires version 2.29.0 or later of the Azure CLI. If using Azure Cloud Shell, the latest version is already installed.

  • You must install the Azure CLI on the machine that will run the example flowgraph.

  • If running on a virtual machine in Azure, you must not enable a managed identity. The Key Vault block uses the DefaultAzureCredential class for authentication, which will use the managed identity for authentication if it is enabled, ignoring credentials provided by az login. Follow these instructions to confirm whether or not your virtual machine has a managed identity enabled.

Set Up Storage in Azure

To run the examples in this quickstart you must first create the necessary resources in Azure. You can either click the button below to deploy a new storage account and blob container for testing, or you can follow Azure tutorials on how to deploy the blob resources manually.

(Choose One)

  1. Deploy Resources Automatically

    1. Click
    2. You will have to pick a new or existing resource group to assign the new resources to
    3. The default value for Storage Account Name might look confusing but if you leave it as is, it will create a new one with a globally unique name to avoid conflicts, such as storageaccountgeh5jwaddf7tc. You are welcome to replace the entire string with your own unique name, it may contain numbers and lowercase letters only because it will be part of a URL.
    4. The container name does not have to be unique, but make note of what you called it.

  2. Deploy Resources Manually

    1. Set up a storage account in your Azure subscription, see: https://docs.microsoft.com/en-us/azure/storage/common/storage-account-create
    2. Add a container in that storage account, see: https://docs.microsoft.com/en-us/azure/storage/blobs/storage-quickstart-blobs-portal#create-a-container

Next, remote desktop into your VM.

Determine Blob Authentication

You will need to choose how to authenticate to the blob storage account. This example is set up to use the "default" authentication option, which uses the DefaultAzureCredential class to attempt to authenticate to the blob storage backend with a list of credential types in priority order.

The instructions below use the Azure CLI to configure access to Azure storage. See https://docs.microsoft.com/en-us/cli/azure/get-started-with-azure-cli to get started with the Azure CLI, or use the browser accessible Azure Cloud Shell to start using the Azure CLI without installing any dependencies: https://docs.microsoft.com/en-us/azure/cloud-shell/overview

In this quickstart it is assuming you are on a VM with a managed identity enabled, you can give the VM permissions to use the storage account using the following steps. For a different version of this quickstart where managed identity disabled, or you are not running on an Azure VM, see this quickstart.

In a terminal on your VM:

  1. Get the service principal ID for the VM's managed identity by running: 
    spID=$(az vm identity show --name MyVirtualMachine --resource-group myResourceGroup --query principalId --out tsv)
  2. Get the Azure ID of your storage account by running: 
    storageID=$(az resource list --name MyStorageAccountName --query [*].id --out tsv)
  3. Give the VM full permissions to read and write to the storage account by assigning it the "Storage Blob Data Owner" role: 
    az role assignment create --assignee $spID --role 'Storage Blob Data Owner' --scope $storageID

See https://docs.microsoft.com/en-us/azure/active-directory/managed-identities-azure-resources/howto-assign-access-cli for more details on using the Azure CLI to manage access to resources.

Next, open GNU Radio using:

gnuradio-companion

Run the Blob Sink Example

Open blob-sink-example.grc.

To run the flowgraph, you must:

  • Change the blob_url variable to use your actual storage account URL
  • Change the blob_container_name variable to use the container name you created

Run the flowgraph for a few seconds, then stop it (e.g., by closing the window that popped up). Navigate to your blob container in the Azure portal and you should see a new blob object named "test-signal.dat". The number of samples simulated and stored depends on how long you ran the flowgraph, but the blob_block_length defines the maximum (defaults to 10M samples).

Run the Blob Source Example

Open blob-source-example.grc.

To run the flowgraph, you must:

  • Change the blob_url variable to use your actual storage account URL
  • Change the blob_container_name variable to use the container name you created
  • Change the blob_name to point to an existing blob object, which is test-signal.dat assuming you did the previous section to completion.

Run the flowgraph and you should see the QT GUI Sink block showing the contents of your blob object, which is the signal we simulated in the previous section.

Once you are done with running the examples, delete the resources you created to ensure you do not incur ongoing charges for storage.

Recommended content

Azure Blob storage overview