In this article, we will explore how to create a serverless application using Azure Functions and utilize Azure SQL Database to log messages generated by the function. Serverless applications have become increasingly popular in the world of cloud-based applications, and it is crucial to understand how to design and create them effectively. One important aspect of application design is generating log messages at key steps or operations to aid in troubleshooting and debugging.

Logging is a broad concept in programming, but it is generally recommended to categorize log messages and log each category accordingly. For example, log messages can be classified as information, warning, or error. You can further customize the categorization based on your specific needs. These logged messages can be stored in various ways, such as simple text files, log files, log streams in cloud services like AWS CloudWatch or Azure Monitor. Alternatively, you can choose to build your own custom logger and store log messages in a database or datastore of your choice.

In this article, we will focus on storing log messages from a Function App to an Azure SQL database. We will assume that you have a fair knowledge of writing simple SQL scripts to insert and view data from a database.

Creating an Azure SQL Database

First, let’s create an Azure SQL Database to store our log messages from the Function App. Navigate to the Azure portal (https://portal.azure.com) and search for “SQL Database”. Select SQL databases from the dropdown menu. In the Create SQL Database pane, provide the relevant details to create the SQL database. If necessary, you can also create a new SQL Server Database if you don’t have an existing server. Once you have provided all the necessary details, click on Create. It may take some time to create all the resources. Once done, you will see a deployment success screen. Click Go to resource on this page to proceed.

Connecting to the Azure SQL Database

Once the database has been successfully deployed, we can connect to it. Copy the Server Name from the resources page and use it to connect to the SQL Server using your client application. For example, if you are using Azure Data Studio on MacOS, you can use it to connect to the server. Alternatively, you can also use SQL Server Management Studio to connect. Once logged in, you can navigate through the databases and perform various operations.

Creating a Table for Log Messages

Let’s create a simple table that can be used to store the log messages. You can use the following SQL script to create the table:

CREATE TABLE [dbo].[ApplicationLogs] (
    [Id] [INT] IDENTITY(1,1) NOT NULL,
    [LogMessage] [NVARCHAR](MAX) NULL,
    [CreateDate] [DATETIME] NULL,
    CONSTRAINT [PK_Logs] PRIMARY KEY CLUSTERED ([Id] ASC)
)

INSERT INTO [ApplicationLogs] ([LogMessage], [CreateDate])
VALUES ('This is a test log message.', GETDATE())

SELECT * FROM [ApplicationLogs]

This script creates a table called “ApplicationLogs” with three columns: Id, LogMessage, and CreateDate. It also inserts a dummy record into the table to test if the script works correctly.

Storing the Connection String

Next, we need to store the connection string for the database. Click on Show database connection strings under the database Overview pane. Your connection string will appear in the tab below. Make sure to replace the password with the one you have set.

Creating the Azure Function

Now that our database is ready, let’s create the Azure Function. Navigate to the Azure portal (https://portal.azure.com) and search for “Function App”. Click Create to create a new Azure Function App. In the next pane, select a resource group, provide a name for the function, and choose the publish type, runtime stack, version, and region. These details are required to configure the function app and create the necessary resources. Once you have provided all the required information, click on Review + Create. After the function app is created, you will see a message indicating that the deployment has been completed. Click on Go to resource on this page to proceed.

Configuring the Function

On the Functions page, click on Functions and then on Add to create a new function. Select HTTP Trigger from the right-side pane. You can now create the function code, view and test it. Once you have created the function code, you can obtain the function URL and test it by pasting it into the address bar of your browser. You can also append “&name=yourname” at the end of the query to display a personalized message.

Adding Database Connectivity

To log messages to the Azure SQL Database every time the function is triggered, we need to modify the code and add a few lines of code for database connectivity. You can use the provided code snippet and update the connection string accordingly. Once you deploy this code to the Function App in Azure and run it using the browser, you can check the records inserted by the application into the Azure SQL Database.

Conclusion

In this article, we have learned how to build a serverless application using Azure Functions and log messages to an Azure SQL Database. Logging is an essential part of any live application as it helps troubleshoot issues. Azure provides various options for storing and viewing logs, including pre-built monitoring services and visualization tools. By following the steps outlined in this article, you can create a serverless application that effectively logs messages to an Azure SQL Database.