Deploying a Flask Application to AWS Elastic Beanstalk
This tutorial walks through the deployment of a simple Flask website to an Elastic Beanstalk environment running Python 2.7. The tutorial uses the EB CLI as a deployment mechanism, but you can also use the AWS Management Console to deploy a ZIP file containing your project's contents. The EB CLI is an interactive command line interface written in Python that uses the Python SDK for AWS (boto).
To use any Amazon Web Service (AWS), including Elastic Beanstalk, you need to have an AWS account and credentials. To learn more and to sign up, visit https://aws.amazon.com/.
To follow this tutorial, you should have all of the Common Prerequisites for Python installed, including the following packages:
The Flask framework will be installed as part of the tutorial.
Creating environments with the EB CLI requires a service role. You can create a service role by creating an environment in the Elastic Beanstalk
Management Console. If you don't have a service role, the EB CLI will attempt to create one when
Set Up a Python Virtual Environment with Flask
Create a virtual environment with virtualenv and use it to install Flask and its dependencies. By using a virtual environment, you can discern exactly which packages are needed by your application so that the required packages are installed on the EC2 instances that are running your application.
To set up your virtual environment
Create a virtual environment named
Activate the virtual environment:
source ~/eb-virt/bin/activate(eb-virt) ~$
You will see
(eb-virt)prepended to your command prompt, indicating that you're in a virtual environment.
Use pip to install Flask by typing:
pip install flask==0.10.1
To verify that Flask has been installed, type:
pip freezeFlask==0.10.1 itsdangerous==0.24 Jinja2==2.7.3 MarkupSafe==0.23 Werkzeug==0.10.1
This command lists all of the packages installed in your virtual environment. Later you will use the output of this command to configure your project for use with Elastic Beanstalk.
Create a Flask Application
Next, create an application that you'll deploy using Elastic Beanstalk. We'll create a "Hello World" RESTful web service.
To create the Hello World Flask application
Activate your virtual environment:
Create a directory for your project named
Create a new text file in this directory named
application.pywith the following contents:
from flask import Flask # print a nice greeting. def say_hello(username = "World"): return '<p>Hello %s!</p>\n' % username # some bits of text for the page. header_text = ''' <html>\n<head> <title>EB Flask Test</title> </head>\n<body>''' instructions = ''' <p><em>Hint</em>: This is a RESTful web service! Append a username to the URL (for example: <code>/Thelonious</code>) to say hello to someone specific.</p>\n''' home_link = '<p><a href="/">Back</a></p>\n' footer_text = '</body>\n</html>' # EB looks for an 'application' callable by default. application = Flask(__name__) # add a rule for the index page. application.add_url_rule('/', 'index', (lambda: header_text + say_hello() + instructions + footer_text)) # add a rule when the page is accessed with a name appended to the site # URL. application.add_url_rule('/<username>', 'hello', (lambda username: header_text + say_hello(username) + home_link + footer_text)) # run the app. if __name__ == "__main__": # Setting debug to True enables debug output. This line should be # removed before deploying a production app. application.debug = True application.run()
This example prints a customized greeting that varies based on the path used to access the service.
application.debug = Truebefore running the application, debug output is enabled in case something goes wrong. It's a good practice for development, but you should remove debug statements in production code, since debug output can reveal internal aspects of your application.
application.pyas the filename and providing a callable
applicationobject (the Flask object, in this case) allows Elastic Beanstalk to easily find your application's code.
Flask will start a web server and display the URL to access your application with. For example:
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit) * Restarting with stat
Open the URL in your web browser. You should see the application running, showing the index page:
Check the server log to see the output from your request. You can stop the web server and return to your virtual environment by typing Ctrl+C.
If you got debug output instead, fix the errors and make sure the application is running locally before configuring it for Elastic Beanstalk.
Configure Your Flask Application for Elastic Beanstalk
With your application running locally, you're now ready to configure it to deploy with Elastic Beanstalk.
To configure your site for Elastic Beanstalk
Activate your virtual environment:
pip freezeand save the output to a file named
pip freeze > requirements.txt
Elastic Beanstalk uses to
requirements.txtto determine which package to install on the EC2 instances that run your application.
Deactivate your virtual environment by with the
Reactivate your virtual environment whenever you need to add additional packages to your application or run your application locally.
Deploy Your Site With the EB CLI
You've added everything you need to deploy your application on Elastic Beanstalk. Your project directory should now look like this:
~/eb-flask/ |-- application.py `-- requirements.txt
Next, you'll create your application environment and deploy your configured application with Elastic Beanstalk.
To create an environment and deploy your Flask application
Initialize your EB CLI repository with the
eb init -p python2.7 flask-tutorialApplication flask-tutorial has been created.
This command creates a new application named
flask-tutorialand configures your local repository to create environments with the latest Python 2.7 platform configuration.
eb initagain to configure a default keypair so that you can connect to the EC2 instance running your application with SSH:
eb initDo you want to set up SSH for your instances? (y/n):
ySelect a keypair. 1) my-keypair 2) [ Create new KeyPair ]
Select a key pair if you have one already, or follow the prompts to create a new one. If you don't see the prompt or need to change your settings later, run
eb init -i.
Create an environment and deploy you application to it with
eb create flask-env
If you see a "service role required" error message, run
eb createinteractively (without specifying an environment name) and the EB CLI will create the role for you.
This command creates a load balanced Elastic Beanstalk environment named
flask-env. Creating an environment takes about 5 minutes. As Elastic Beanstalk creates the resources necessary to run your application, it outputs informational messages that the EB CLI relays to your terminal.
When the environment creation process completes, open your web site with
This will open a browser window using the domain name created for your application. You should see the same Flask website that you created and tested locally.
If you don't see your application running, or get an error message, see Troubleshooting deployments for help with how to determine the cause of the error.
If you do see your application running, then congratulations, you've deployed your first Flask application with Elastic Beanstalk!
Clean Up and Next Steps
To save instance hours and other AWS resources between development sessions, terminate
your Elastic Beanstalk environment with
eb terminate flask-env
This command terminates the environment and all of the AWS resources that run within it.
It does not delete the application, however, so you can always create more environments with
the same configuration by running
eb create again. For more information on EB CLI
commands, see Managing Elastic Beanstalk Environments with the EB CLI.
If you are done with the sample application, you can also remove the project folder and virtual environment:
rm -rf ~/eb-virt~$
rm -rf ~/eb-flask
For more information about Flask, including an in-depth tutorial, visit the official documentation.
If you'd like to try out another Python web framework, check out Deploying a Django Application to Elastic Beanstalk.