Function Compute:Create a web application with a web function

Step 1: Develop and test the application

1. Open a new command-line window on your local machine and run the following command to install the required Flask and tabulate libraries.

   pip install Flask tabulate

2. Create a folder named code and a file named app.py within it. Paste the following sample code into the file. This code implements a simple calendar service that is packaged as an API. The API accepts a year and month, such as January 2025, and returns a calendar table for that month.

   import calendar
   from flask import Flask, request
   from tabulate import tabulate
   import logging
   import json
   
   logger = logging.getLogger()
   app = Flask(__name__)
   
   
   @app.route("/", methods=["POST"])
   def get_month_calendar():
       # Get the request ID and print the log.
       requestId = request.headers.get('x-fc-request-id', '')
       logger.info("FC Invoke Start RequestId: " + requestId)
       # Get the request content and check the request format.
       data = json.loads(request.stream.read().decode('utf-8'))
       if not ('year' in data and 'month' in data):
           message = "Request must be in format like {'year': '1999', 'month': '12'}"
           return message
   
       # Get the calendar table.
       result = print_calendar(year=int(data['year']), month=int(data['month']))
       # Print the log that indicates the function execution is complete before the result is returned.
       logger.info("FC Invoke End RequestId: " + requestId)
       return result
   
   
   def print_calendar(year, month):
       # Get the calendar matrix for the specified year and month.
       cal = calendar.monthcalendar(year, month)
       # Change the dates that do not belong to the month from 0 to empty strings.
       cal = list(map(lambda sublist: list(map(lambda x: '' if x == 0 else x, sublist)), cal))
       # Create table headers.
       headers = ["Mo", "Tu", "We", "Th", "Fr", "Sa", "Su"]
   
       # Use tabulate to print the calendar table.
       return tabulate(cal, headers=headers, tablefmt="grid", stralign='center', numalign='center')
   
   
   if __name__ == "__main__":
       app.run(host='0.0.0.0', port=9000)
   

3. Run the python3 app.py command to run your Flask application. If the output Running on http://127.0.0.1:9000 is displayed, the Flask application is running. You can then use a cURL command to test the application.

   python3 app.py 
    * Serving Flask app 'app'
    * Debug mode: off
   WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead.
    * Running on http://127.0.0.1:9000
    * Running on http://47.100.XX.XX:9000
   Press CTRL+C to quit

4. Open a new terminal window and use cURL to send a sample request. A successful command returns a calendar table.

   curl -X POST http://127.0.0.1:9000 -d '{"year": "2000", "month": "1"}'

   

You have now created and tested the project locally.

Step 2: Generate a code package

You will build a code package locally that is suitable for Function Compute. The code package must contain the following content:

• The project files required by the web application.

• If your application has dependencies that are not included in the runtime, you must add them to the code package. For information about the built-in dependencies for runtimes, see Built-in dependencies.

1. Install dependencies: In the root directory of your web application project, run the following command to install the required dependencies (in this example, tabulate) into that directory. This command installs the dependencies into your project's root directory.

   Note

   The Python web function runtime already includes the Flask library. You only need to install the tabulate library for the sample application to work.

   pip install -t . tabulate

2. Package all files in the project root directory.

   Linux or macOS

   In the project root directory, run the zip code.zip -r ./* command. This command packages the project files and dependencies into a ZIP file, creating the code package.

   Note

   Make sure that you have read and write permissions on the directory.

   Windows

   Go to the project directory, select all files, right-click the files, and then package them into a ZIP file. This packages the project files and dependencies into a ZIP file, creating the code package.

Step 3: Create and deploy the function

1. Select the web function type: Sign in to the Function Compute console. In the left-side navigation pane, click Function Management > Functions. In the top navigation bar, select the region where you want to create the function. On the page that appears, click Create Function, and then follow the on-screen instructions to create a Web Function.

2. Select a runtime: As shown in the following figure, select Custom Runtime. This runtime has the dependencies that are required by the Flask framework.

   Note

   • We recommend using a Custom Runtime for your web function. A Custom Runtime lets you specify a startup command and a listening port, and supports concurrent request handling. A Built-in Runtimes does not provide these features and is more suitable for handling events that are generated by other cloud services.

   • If you prefer containerized deployment, you can use a Custom Container to create a web function. This runtime also supports concurrent request handling, but you must manage the dependencies yourself.

   • For a detailed comparison of runtimes, see Select a runtime.

3. Deploy the code package: As shown in the figure, upload the ZIP code package that you created in Step 2. Set the startup command to python3 app.py and the listening port to 9000. If you are migrating an existing Flask application, modify the configuration based on the actual startup command and port. For example, Flask's default port is 5000.

   Click Create and wait for the function to be created.

Step 4: Test the function

1. Obtain the function URL: On the details page of the newly created function, click the Trigger tab. In the HTTP trigger configuration, copy the public endpoint.

   If you are in a test environment and do not need authentication, you can change the Authentication Method to No Authentication in the HTTP trigger's configuration when or after creating the trigger.

   

2. Test the function: You can use cURL, Postman, or any HTTP client to invoke the function and verify that the Flask application works as expected. The following example uses a cURL command. Replace the URL with the endpoint that you copied in the previous step.

   curl https://******.cn-hangzhou.fcapp.run -d '{"year": "2025", "month": "1"}' 

   The web API returns the calendar information for January 2025. The following output is a sample.

   

   Note

   • If you use the default HTTP trigger configuration, the command returns a "MissingRequiredHeader" error. If you are in a test environment, you can change the Authentication Method of the trigger to No Authentication.

   • The sample command and output in this step apply only to the sample code. If you migrate an existing application, invoke the service based on the actual API name and parameters. For more information, see Use cURL to test a function.

3. (Optional) Access the function from a browser: The public endpoint provided by the HTTP trigger cannot be opened directly in a browser (which may trigger a forced download) and is intended for testing purposes only. We recommend that you bind a custom domain name to the function to enable browser access and for use in a production environment. For more information, see Configure a custom domain name.

(Optional) Step 5: Clean up resources

For more information about how to add dependency packages for different languages, see the following topics: