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--- title: Tutorial - Trigger a Batch job using Azure Functions description: Learn how to apply OCR to scanned documents as they're added to a storage blob by using Azure Function Apps. ms.devlang: csharp ms.topic: tutorial ms.date: 06/16/2026 ms.custom: mvc, devx-track-csharp # Customer intent: As a developer, I want to create an Azure Function that triggers a Batch job for OCR processing, so that I can automate the conversion of scanned documents into searchable text files upon upload. --- # Tutorial: Trigger a Batch job using Azure Functions In this tutorial, you learn how to trigger a Batch job using [Azure Functions](../azure-functions/functions-overview.md). This article walks through an example that takes documents added to an Azure Storage blob container and applies optical character recognition (OCR) to them by using Azure Batch. To streamline the OCR processing, this example configures an Azure function that runs a Batch OCR job each time a file is added to the blob container. You learn how to: * Use the Azure portal to create pools and jobs. * Create blob containers and a shared access signature (SAS). * Create a blob-triggered Azure Function. * Upload input files to Storage. * Monitor task execution. * Retrieve output files. ## Prerequisites * An Azure account with an active subscription. [Create an account for free](https://azure.microsoft.com/pricing/purchase-options/azure-account?cid=msft_learn). * An Azure Batch account and a linked Azure Storage account. For more information on how to create and link accounts, see [Create a Batch account](quick-create-portal.md#create-a-batch-account). ## Sign in to Azure Sign in to the [Azure portal](https://portal.azure.com). ## Create a Batch pool and Batch job using the Azure portal In this section, you use the Azure portal to create the Batch pool and Batch job that runs OCR tasks. ### Create a pool 1. Sign in to the Azure portal using your Azure credentials. 1. Create a pool by selecting **Pools** on the left side navigation, and then select the **Add** button above the search form. :::image type="content" source="./media/tutorial-batch-functions/add-pool.png" alt-text="Screenshot of the Pools page in a Batch account that highlights the Add button."::: 1. Enter a **Pool ID**. This example names the pool `ocr-pool`. 1. Select **canonical** as the **Publisher**. 1. Select **0001-com-ubuntu-server-jammy** as the **Offer**. 1. Select **22_04-lts** as the **Sku**. 1. Choose `Standard_F2s_v2 - 2 vCPUs, 2 GB Memory` as the **VM size** in the **Node Size** section. 1. Set the **Mode** in the **Scale** section to **Fixed**, and enter 3 for the **Target dedicated nodes**. 1. Set **Start task** to **Enabled** the start task, and enter the command `/bin/bash -c "sudo update-locale LC_ALL=C.UTF-8 LANG=C.UTF-8; sudo apt-get update; sudo apt-get -y install ocrmypdf"` in **Command line**. Be sure to set the **Elevation level** as **Pool autouser, Admin**, which allows start tasks to include commands with `sudo`. 1. Select **OK**. ### Create a job 1. Create a job on the pool by selecting **Jobs** in the left side navigation, and then choose the **Add** button above the search form. 1. Enter a **Job ID**. This example uses `ocr-job`. 1. Select `ocr-pool` for **Current pool**, or whatever name you chose for your pool. 1. Select **OK**. ## Create blob containers Here you create blob containers that store your input and output files for the OCR Batch job. In this example, the input container is named `input` and is where all documents without OCR are initially uploaded for processing. The output container is named `output` and is where the Batch job writes processed documents with OCR. 1. Search for and select **Storage accounts** in the Azure portal. 1. Choose your storage account linked to your Batch account. 1. Select **Containers** from the left side navigation, and create two blob containers (one for input files, one for output files) by following the steps at [Create a blob container](../vs-azure-tools-storage-explorer-blobs.md#create-a-blob-container). 1. Create a shared access signature for your output container by selecting the output container, and on the **Shared access tokens** page, select **Write** in the **Permissions** drop down. No other permissions are necessary. 1. Select **Generate SAS token and URL**, and copy the **Blob SAS URL** to use later for your function. :::image type="content" source="./media/tutorial-batch-functions/shared-access-tokens.png" alt-text="Screenshot of the Shared access tokens page that highlights the Permissions dropdown and the Generate SAS token and URL button."::: ## Create an Azure Function In this section, you create the Azure Function that triggers the OCR Batch job whenever a file is uploaded to your input container. 1. Follow the steps in [Create a function triggered by Azure Blob storage](../azure-functions/functions-create-storage-blob-triggered-function.md) to create a function. 1. For **runtime stack**, choose .NET. This example function uses C# to take advantage of the Batch .NET SDK. 1. On the **Storage** page, use the same storage account that you linked to your Batch account. 1. Select **Review + Create > Create**. The following screenshot the **Create Function App** page on the **Basics** tab using example information. :::image type="content" source="./media/tutorial-batch-functions/create-function-app.png" alt-text="Screenshot of the Create Function App page on the Basics tab using example information." lightbox="./media/tutorial-batch-functions/create-function-app-lightbox.png"::: 1. In your function, select **Functions** from the left side navigation and select **Create**. 1. In the **Create function** pane, select Azure Blob Storage trigger. 1. Enter a name for your function in **New Function**. In this example, the name is OcrTrigger. Enter the path as `input/{name}`, where input in the name of your Blob container. 1. Select **Create**. :::image type="content" source="./media/tutorial-batch-functions/create-azure-blob-storage-trigger.png" alt-text="Screenshot of the Create Function pane that highlights the Azure Blob Storage trigger option and New Function and Path Fields." lightbox="./media/tutorial-batch-functions/create-azure-blob-storage-trigger-lightbox.png"::: 1. Once the blob-triggered function is created, select **Code + Test**. Use the [`run.csx`](https://github.com/Azure-Samples/batch-functions-tutorial/blob/master/run.csx) and [`function.proj`](https://github.com/Azure-Samples/batch-functions-tutorial/blob/master/function.proj) from GitHub in the Function. `function.proj` doesn't exist by default, so select the **Upload** button to upload it into your development workspace. * `run.csx` is run when a new blob is added to your input blob container. * `function.proj` lists the external libraries in your Function code, for example, the Batch .NET SDK. 1. Change the placeholder values of the variables in the `Run()` function of the `run.csx` file to reflect your Batch and storage credentials. You can find your Batch and storage account credentials in the Azure portal in the **Keys** section of your Batch and storage account. ## Trigger the function and retrieve results Upload any or all of the scanned files from the [`input_files`](https://github.com/Azure-Samples/batch-functions-tutorial/tree/master/input_files) directory on GitHub to your input container. You can test your function from Azure portal on the **Code + Test** page of your function. 1. Select **Test/run** on the **Code + Test** page. 1. Enter the path for your input container in **Body** on the **Input** tab. 1. Select **Run**. After a few seconds, the file with OCR applied is added to the output container. Log information outputs to the bottom window. The file is then visible and retrievable on Storage Explorer. Alternatively, you can find the log information on the **Monitor** page: ```console 2019-05-29T19:45:25.846 [Information] Creating job... 2019-05-29T19:45:25.847 [Information] Accessing input container <inputContainer>... 2019-05-29T19:45:25.847 [Information] Adding <fileName> as a resource file... 2019-05-29T19:45:25.848 [Information] Name of output text file: <outputTxtFile> 2019-05-29T19:45:25.848 [Information] Name of output PDF file: <outputPdfFile> 2019-05-29T19:45:26.200 [Information] Adding OCR task <taskID> for <fileName> <size of fileName>... ``` To download the output files to your local machine, go to the output container in your storage account. Select more options on the file you want, and then select **Download**. > [!TIP] > The downloaded files are searchable if opened in a PDF reader. ## Clean up resources You're charged for the pool while the nodes are running, even if no jobs are scheduled. When you no longer need the pool, delete it with the following steps: 1. From the **Pools** page of your Batch account, select more options on your pool. 1. Select **Delete**. When you delete the pool, all task output on the nodes is deleted. However, the output files remain in the storage account. When no longer needed, you can also delete the Batch account and the storage account. ## Next steps For more examples of using the .NET API to schedule and process Batch workloads, see the samples on GitHub. * [Batch C# samples](https://github.com/Azure-Samples/azure-batch-samples/tree/master/CSharp)