Fetching and Publishing Settings for Azure Functions with Azure Functions Core Tools Command Line

#azure #azurefunctions #tooling #webdev

During my daily activities I develop a lot of Azure Functions. Every time I struggle to synchronize my local settings to the remote settings on Azure.

In this article, I will show you how to use the Core Tools to fetch and publish settings for Azure Functions. By using the Core Tools, you can ensure that your local and remote environments are consistent and avoid errors due to missing or outdated settings.

Let’s get started!

Fetching Settings from Azure

If you have already deployed your Azure Functions project to Azure, you may want to fetch the settings from the cloud and apply them to your local project. This can help you ensure that your local and remote environments are consistent and avoid errors due to missing or outdated settings.

To fetch settings from Azure, you can use the func azure functionapp fetch-app-settings command. This command downloads the settings from your Azure Function App and stores them in a local file named local.settings.json. This file is used by the Core Tools to load the settings when you run your functions locally.

The syntax of the command is:

func azure functionapp fetch-app-settings <function-app-name>

where <function-app-name> is the name of your Azure Function App.

For example, if your Azure Function App is named my-function-app, you can run the following command:

func azure functionapp fetch-app-settings my-function-app

This will download the settings from my-function-app and save them in local.settings.json.

You can view the contents of local.settings.json using any text editor. The file has the following structure:

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "<storage-account-connection-string>",
    "FUNCTIONS_WORKER_RUNTIME": "<worker-runtime>",
    "FUNCTIONS_EXTENSION_VERSION": "<extension-version>",
    // other app settings
  },
  "ConnectionStrings": {
    // connection strings
  },
  "Host": {
    // host settings
  }
}

The Values section contains the app settings, such as the storage account connection string, the worker runtime, the extension version, and any custom settings you have defined. The ConnectionStrings section contains the connection strings for your data sources, such as Azure SQL Database, Cosmos DB, Service Bus, etc. The Host section contains the host settings, such as the HTTP route prefix, the CORS policy, the logging level, etc.

Note that the IsEncrypted property is set to false, which means that the settings are stored in plain text. This is fine for local development, but you should not commit this file to source control or share it with others. If you want to encrypt the settings, you can use the func settings encrypt command.

Publishing Settings to Azure

If you have made changes to your local settings and want to apply them to your Azure Function App, you can use the func azure functionapp publish command. This command deploys your Azure Functions project to Azure and optionally updates the settings on the cloud.

The syntax of the command is:

func azure functionapp publish <function-app-name> [options]

where <function-app-name> is the name of your Azure Function App and [options] are optional parameters that control the behavior of the command.

Some of the options that are relevant for publishing settings are:

-publish-local-settings: This option publishes all the settings in local.settings.json to your Azure Function App. This will overwrite any existing settings on the cloud with the same name. If you want to exclude some settings from being published, you can use the -publish-settings-only option instead and specify the settings you want to publish.
-overwrite-settings: This option forces the command to overwrite the settings on the cloud even if they have been modified since the last fetch. By default, the command will prompt you to confirm the overwrite if it detects any changes.
-nozip: This option disables the zip deployment method and uses the run-from-package method instead. This can improve the performance and reliability of your Azure Function App, but it requires that your project folder is accessible from the cloud. For more information, see [here].

For example, if you want to publish your local project and settings to my-function-app using the run-from-package method and overwrite any existing settings, you can run the following command:

func azure functionapp publish my-function-app --publish-local-settings --overwrite-settings --nozip

This will deploy your project and settings to my-function-app and display the output of the command.

Conclusion

In this article, I have shown you how to use the Azure Functions Core Tools to fetch and publish settings for Azure Functions.
You can use the Core Tools to download the settings from your Azure Function App and save them in a local file named local.settings.json. You can also use the Core Tools to deploy your project and settings to your Azure Function App and optionally overwrite the existing settings on the cloud. By using the Core Tools, you can ensure that your local and remote environments are consistent and avoid errors due to missing or outdated settings.

Thanks for reading and keep learning!

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