Sample: Load data from SQL using Python and Azure Functions

• Code Sample
• 05/04/2023
• 2 contributors

How do I transfer data from Azure SQL Database in Python every day?

• Scenario 1: Generate .txt files from data currently stored in Azure SQL Database and send the files to an FTP server
• Scenario 2: Take data from the Azure SQL Database and send the data to an API endpoint

Contents

Prerequisites to local development

1. Complete the Configure your environment steps to setup your local development environment for Azure Functions.
2. If you don't have a SQL database, either run SQL Server in a container or create an Azure SQL Database.

Setup

1. Clone this repository to your local machine.
2. Open the folder in Visual Studio Code.
3. Copy local.settings.json.sample to local.settings.json and update the values for SqlConnectionString, FTP_HOST, FTP_USER, and FTP_PASS with your own values.

Running the sample

1. Start the function locally by pressing F5 in Visual Studio Code or the Run and Debug icon in the left-hand side Activity bar.
2. Manually invoke the timer triggers using the built-in HTTP endpoint.

Scenario 1: write to an FTP server

To write data to an FTP server, we can use the built-in library ftplib in Python.

• More about ftplib: https://docs.python.org/3/library/ftplib.html
• More about pandas to_csv: https://pandas.pydata.org/docs/reference/api/pandas.DataFrame.to_csv.html
• Test FTP server: https://dlptest.com/ftp-test/
• Sample function code: SendDataToFTP

def main(everyDayAt5AM: func.TimerRequest, products: func.SqlRowList) -> func.HttpResponse:
    logging.info('Python HTTP trigger function processed a request.')
    filename = "products.txt"
    filesize = 0

    # convert the SQL data to comma separated text
    product_list = pandas.DataFrame(products)
    product_csv = product_list.to_csv(index=False)
    datatosend = io.BytesIO(product_csv.encode('utf-8'))

    # get FTP connection details from app settings
    FTP_HOST = os.environ['FTP_HOST']
    FTP_USER = os.environ['FTP_USER']
    FTP_PASS = os.environ['FTP_PASS']

    # connect to the FTP server
    try:
        with ftplib.FTP(FTP_HOST, FTP_USER, FTP_PASS, encoding="utf-8") as ftp:
            logging.info(ftp.getwelcome())
            # use FTP's STOR command to upload the data
            ftp.storbinary(f"STOR {filename}", datatosend)
            filesize = ftp.size(filename)
            ftp.quit()
    except Exception as e:
        logging.error(e)

    logging.info(f"File {filename} uploaded to FTP server. Size: {filesize} bytes")

Scenario 2: send data to an API endpoint

To send the data from the SQL input binding to an API endpoint from the Azure Function, we can import the requests library and use it to make a POST request to the API endpoint.

• More about requests: https://requests.readthedocs.io/en/latest/user/quickstart/
• Sample function code: SendDataToAPI

def main(everyDayAt5AM: func.TimerRequest, products: func.SqlRowList) -> None:
    logging.info('Python timer trigger function started')
    # convert the SQL data to JSON in memory
    rows = list(map(lambda r: json.loads(r.to_json()), products))

    # get the API endpoint from app settings
    api_url = os.environ['API_URL']

    # send the data to the API
    response = requests.post(api_url, json=rows)
    # check for 2xx status code
    if response.status_code // 100 != 2:
        logging.error(f"API response: {response.status_code} {response.reason}")
    else:
        logging.info(f"API response: {response.status_code} {response.reason}")

Key concepts

Get data from Azure SQL Database in Azure Functions

With Azure SQL bindings for Azure Functions, we can easily retrieve data from an Azure SQL Database in an Azure Function.

We retrieve data from SQL using an input binding for Azure Functions by adding the following to the function.json file:

{
    "name": "products",
    "type": "sql",
    "direction": "in",
    "commandText": "SELECT [ProductID],[Name],[ProductModel],[Description] FROM [SalesLT].[vProductAndDescription]",
    "commandType": "Text",
    "connectionStringSetting": "SqlConnectionString"
}

In this input binding, we are specifying a query to run against the database in the commandText property. We also specify the connectionStringSetting which is the name of the connection string in the local.settings.json file and Azure Functions app settings.

The output of that query is passed to the Azure Function as the parameter products, specified by the json property name.

Azure Functions timer trigger

For tasks that need to run on a schedule, we can use the timer trigger for Azure Functions.

A few notes:

• The timer trigger assumes UTC time, and the WEBSITE_TIME_ZONE app setting is available only for certain hosts.
• Timer triggers use NCRONTAB expressions to set the schedule, which is similar to CRON but with an additional field for seconds ({second} {minute} {hour} {day} {month} {day-of-week}).

{
    "name": "everyDayAt5AM",
    "type": "timerTrigger",
    "direction": "in",
    "schedule": "0 0 5 * * *"
}