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      How To Serve Flask Applications with uWSGI and Nginx on Ubuntu 20.04


      Not using Ubuntu 20.04?


      Choose a different version or distribution.

      A previous version of this tutorial was written by Justin Ellingwood

      Introduction

      In this guide, you will build a Python application using the Flask microframework on Ubuntu 20.04. The bulk of this article will be about how to set up the uWSGI application server and how to launch the application and configure Nginx to act as a front-end reverse proxy.

      Prerequisites

      Before starting this guide, you should have:

      • A server with Ubuntu 20.04 installed and a non-root user with sudo privileges. Follow our initial server setup guide for guidance.
      • Nginx installed, following Steps 1 through 3 of How To Install Nginx on Ubuntu 20.04.
      • A domain name configured to point to your server. You can purchase one on Namecheap or get one for free on Freenom. You can learn how to point domains to DigitalOcean by following the relevant documentation on domains and DNS. This tutorial assumes you’ve created the following DNS records:

        • An A record with your_domain pointing to your server’s public IP address.
        • An A record with www.your_domain pointing to your server’s public IP address.

      Additionally, it may be helpful to have some familiarity with uWSGI, the application server you’ll set up in this guide, and the WSGI specification. This discussion of definitions and concepts goes over both in detail.

      Step 1 — Installing the Components from the Ubuntu Repositories

      Your first step will be to install all of the pieces that you need from the Ubuntu repositories. The packages you need to install include pip, the Python package manager, to manage your Python components. You’ll also get the Python development files necessary to build uWSGI.

      First, update the local package index:

      Then install the packages that will allow you to build your Python environment. These will include python3-pip, along with a few more packages and development tools necessary for a robust programming environment:

      • sudo apt install python3-pip python3-dev build-essential libssl-dev libffi-dev python3-setuptools

      With these packages in place, you’re ready to move on to creating a virtual environment for your project.

      Step 2 — Creating a Python Virtual Environment

      A Python virtual environment is a self-contained project directory that contains specific versions of Python and the Python modules required for the given project. This is useful for isolating one application from others on the same system by managing each one’s dependencies separately. In this step, you’ll set up a Python virtual environment from which you’ll run your Flask application.

      Start by installing the python3-venv package, which will install the venv module:

      • sudo apt install python3-venv

      Next, make a parent directory for your Flask project:

      Move into the directory after you create it:

      Create a virtual environment to store your Flask project’s Python requirements by typing:

      • python3.8 -m venv myprojectenv

      This will install a local copy of Python and pip into a directory called myprojectenv within your project directory.

      Before installing applications within the virtual environment, you need to activate it. Do so by typing:

      • source myprojectenv/bin/activate

      Your prompt will change to indicate that you are now operating within the virtual environment. It will look something like this: (myprojectenv)user@host:~/myproject$.

      Step 3 — Setting Up a Flask Application

      Now that you are in your virtual environment, you can install Flask and uWSGI and then get started on designing your application.

      First, install wheel with the local instance of pip to ensure that your packages will install even if they are missing wheel archives:

      Note: Regardless of which version of Python you are using, when the virtual environment is activated, you should use the pip command (not pip3).

      Next, install Flask and uWSGI:

      Creating a Sample App

      Now that you have Flask available, you can create a sample application. Flask is a microframework. It does not include many of the tools that more full-featured frameworks might, and exists mainly as a module that you can import into your projects to assist you in initializing a web application.

      While your application might be more complex, in this example you’ll create your Flask app in a single file, called myproject.py:

      • nano ~/myproject/myproject.py

      The application code will live in this file. It will import Flask and instantiate a Flask object. You can use this to define the functions that you want to be run when a specific route is requested:

      ~/myproject/myproject.py

      from flask import Flask
      app = Flask(__name__)
      
      @app.route("/")
      def hello():
          return "<h1 style="color:blue">Hello There!</h1>"
      
      if __name__ == "__main__":
          app.run(host="0.0.0.0")
      

      Essentially, this defines what content to present to whoever accesses the root domain. Save and close the file when you’re finished. If you used nano to edit the file, as in the previous example, do so by pressing CTRL + X, Y, and then ENTER.

      If you followed the initial server setup guide, you should have a UFW firewall enabled. To test the application, you need to allow access to port 5000:

      Now, you can test your Flask app by typing:

      You will see output like the following, including a helpful warning reminding you not to use this server setup in production:

      Output

      * Serving Flask app "myproject" (lazy loading) * Environment: production WARNING: Do not use the development server in a production environment. Use a production WSGI server instead. * Debug mode: off * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)

      Visit your server’s IP address followed by :5000 in your web browser:

      http://your_server_ip:5000
      

      You will see something like this:

      Flask sample app

      When you are finished, hit CTRL + C in your terminal window to stop the Flask development server.

      Creating the WSGI Entry Point

      Next, create a file that will serve as the entry point for your application. This will tell your uWSGI server how to interact with it.

      Call the file wsgi.py:

      In this file, import the Flask instance from your application and then run it:

      ~/myproject/wsgi.py

      from myproject import app
      
      if __name__ == "__main__":
          app.run()
      

      Save and close the file when you are finished.

      Step 4 — Configuring uWSGI

      Your application is now written with an entry point established. You can move on to configuring uWSGI.

      Testing Whether uWSGI Can Serve the Application

      As a first step, test to make sure that uWSGI can correctly serve your application by passing it the name of your entry point. This is constructed by the name of the module (minus the .py extension) plus the name of the callable within the application. In the context of this tutorial, the name of the entry point is wsgi:app.

      Also, specify the socket so that it will be started on a publicly available interface, as well as the protocol, so that it will use HTTP instead of the uwsgi binary protocol. Use the same port number, 5000, that you opened earlier:

      • uwsgi --socket 0.0.0.0:5000 --protocol=http -w wsgi:app

      Visit your server’s IP address with :5000 appended to the end in your web browser again:

      http://your_server_ip:5000
      

      You will see your application’s output again:

      Flask sample app

      When you have confirmed that it’s functioning properly, press CTRL + C in your terminal window.

      You’re now done with your virtual environment, so you can deactivate it:

      Any Python commands will now use the system’s Python environment again.

      Creating a uWSGI Configuration File

      You have tested that uWSGI is able to serve your application, but ultimately you will want something more robust for long-term usage. You can create a uWSGI configuration file with the relevant options for this.

      Place that file in your project directory and call it myproject.ini:

      • nano ~/myproject/myproject.ini

      Inside, start the file off with the [uwsgi] header so that uWSGI knows to apply the settings. Below that, specify module itself — by referring to the wsgi.py file minus the extension — and the callable within the file, app:

      ~/myproject/myproject.ini

      [uwsgi]
      module = wsgi:app
      

      Next, tell uWSGI to start up in master mode and spawn five worker processes to serve actual requests:

      ~/myproject/myproject.ini

      [uwsgi]
      module = wsgi:app
      
      master = true
      processes = 5
      

      When you were testing, you exposed uWSGI on a network port. However, you’re going to be using Nginx to handle actual client connections, which will then pass requests to uWSGI. Since these components are operating on the same computer, a Unix socket is preferable because it is faster and more secure. Call the socket myproject.sock and place it in this directory.

      Next, change the permissions on the socket. You’ll be giving the Nginx group ownership of the uWSGI process later on, so you need to make sure the group owner of the socket can read information from it and write to it. Also, add the vacuum option and set it to true; this will clean up the socket when the process stops:

      ~/myproject/myproject.ini

      [uwsgi]
      module = wsgi:app
      
      master = true
      processes = 5
      
      socket = myproject.sock
      chmod-socket = 660
      vacuum = true
      

      The last thing to do is set the die-on-term option. This can help ensure that the init system and uWSGI have the same assumptions about what each process signal means. Setting this aligns the two system components, implementing the expected behavior:

      ~/myproject/myproject.ini

      [uwsgi]
      module = wsgi:app
      
      master = true
      processes = 5
      
      socket = myproject.sock
      chmod-socket = 660
      vacuum = true
      
      die-on-term = true
      

      You may have noticed that these lines do not specify a protocol like you did from the command line. That is because by default, uWSGI speaks using the uwsgi protocol, a fast binary protocol designed to communicate with other servers. Nginx can speak this protocol natively, so it’s better to use this than to force communication by HTTP.

      When you are finished, save and close the file.

      With that, uWSGI is configured on your system. In order to give you more flexibility in how you manage your Flask application, you can now configure it to run as a systemd service.

      Step 5 — Creating a systemd Unit File

      Systemd is a suite of tools that provides a fast and flexible init model for managing system services. Creating a systemd unit file will allow Ubuntu’s init system to automatically start uWSGI and serve the Flask application whenever the server boots.

      Create a unit file ending in .service within the /etc/systemd/system directory to begin:

      • sudo nano /etc/systemd/system/myproject.service

      Inside, start with the [Unit] section, which is used to specify metadata and dependencies. Then put a description of the service here and tell the init system to only start this after the networking target has been reached:

      /etc/systemd/system/myproject.service

      [Unit]
      Description=uWSGI instance to serve myproject
      After=network.target
      

      Next, open up the [Service] section. This will specify the user and group that you want the process to run under. Give your regular user account ownership of the process since it owns all of the relevant files. Then give group ownership to the www-data group so that Nginx can communicate easily with the uWSGI processes. Remember to replace the username here with your username:

      /etc/systemd/system/myproject.service

      [Unit]
      Description=uWSGI instance to serve myproject
      After=network.target
      
      [Service]
      User=sammy
      Group=www-data
      

      Next, map out the working directory and set the PATH environmental variable so that the init system knows that the executables for the process are located within your virtual environment. Also, specify the command to start the service. Systemd requires that you give the full path to the uWSGI executable, which is installed within your virtual environment. Here, we pass the name of the .ini configuration file you created in your project directory.

      Remember to replace the username and project paths with your own information:

      /etc/systemd/system/myproject.service

      [Unit]
      Description=uWSGI instance to serve myproject
      After=network.target
      
      [Service]
      User=sammy
      Group=www-data
      WorkingDirectory=/home/sammy/myproject
      Environment="PATH=/home/sammy/myproject/myprojectenv/bin"
      ExecStart=/home/sammy/myproject/myprojectenv/bin/uwsgi --ini myproject.ini
      

      Finally, add an [Install] section. This will tell systemd what to link this service to if you enable it to start at boot. In this case, set the service to start when the regular multi-user system is up and running:

      /etc/systemd/system/myproject.service

      [Unit]
      Description=uWSGI instance to serve myproject
      After=network.target
      
      [Service]
      User=sammy
      Group=www-data
      WorkingDirectory=/home/sammy/myproject
      Environment="PATH=/home/sammy/myproject/myprojectenv/bin"
      ExecStart=/home/sammy/myproject/myprojectenv/bin/uwsgi --ini myproject.ini
      
      [Install]
      WantedBy=multi-user.target
      

      With that, your systemd service file is complete. Save and close it now.

      You can now start the uWSGI service you created:

      • sudo systemctl start myproject

      Then enable it so that it starts at boot:

      • sudo systemctl enable myproject

      Check the status:

      • sudo systemctl status myproject

      You will see output like this:

      Output

      ● myproject.service - uWSGI instance to serve myproject Loaded: loaded (/etc/systemd/system/myproject.service; enabled; vendor preset: enabled) Active: active (running) since Wed 2020-05-20 13:21:39 UTC; 8h ago Main PID: 22146 (uwsgi) Tasks: 6 (limit: 2345) Memory: 25.5M CGroup: /system.slice/myproject.service ├─22146 /home/sammy/myproject/myprojectenv/bin/uwsgi --ini myproject.ini ├─22161 /home/sammy/myproject/myprojectenv/bin/uwsgi --ini myproject.ini ├─22162 /home/sammy/myproject/myprojectenv/bin/uwsgi --ini myproject.ini ├─22163 /home/sammy/myproject/myprojectenv/bin/uwsgi --ini myproject.ini ├─22164 /home/sammy/myproject/myprojectenv/bin/uwsgi --ini myproject.ini └─22165 /home/sammy/myproject/myprojectenv/bin/uwsgi --ini myproject.ini

      If you see any errors, be sure to resolve them before continuing with the tutorial. Otherwise, you can move on to configuring your Nginx installation to pass requests to the myproject.sock socket.

      Step 6 — Configuring Nginx to Proxy Requests

      Your uWSGI application server is now up and running, waiting for requests on the socket file in the project directory. In this step, you’ll configure Nginx to pass web requests to that socket using the uwsgi protocol.

      Begin by creating a new server block configuration file in Nginx’s sites-available directory. To keep in line with the rest of the guide, the following example refers to this as myproject:

      • sudo nano /etc/nginx/sites-available/myproject

      Open up a server block and tell Nginx to listen on the default port 80. Additionally, tell it to use this block for requests for your server’s domain name:

      /etc/nginx/sites-available/myproject

      server {
          listen 80;
          server_name your_domain www.your_domain;
      }
      

      Next, add a location block that matches every request. Within this block, include the uwsgi_params file that specifies some general uWSGI parameters that need to be set. Then pass the requests to the socket you defined using the uwsgi_pass directive:

      /etc/nginx/sites-available/myproject

      server {
          listen 80;
          server_name your_domain www.your_domain;
      
          location / {
              include uwsgi_params;
              uwsgi_pass unix:/home/sammy/myproject/myproject.sock;
          }
      }
      

      Save and close the file when you’re finished.

      To enable the Nginx server block configuration you’ve just created, link the file to the sites-enabled directory:

      • sudo ln -s /etc/nginx/sites-available/myproject /etc/nginx/sites-enabled

      With the file in that directory, you can test for syntax errors by typing:

      If this returns without indicating any issues, restart the Nginx process to read the new configuration:

      • sudo systemctl restart nginx

      Finally, adjust the firewall once again. You no longer need access through port 5000, so you can remove that rule. Then, you can allow access to the Nginx server:

      • sudo ufw delete allow 5000
      • sudo ufw allow 'Nginx Full'

      You will now be able to navigate to your server’s domain name in your web browser:

      http://your_domain
      

      You will see your application output:

      Flask sample app

      If you encounter any errors, trying checking the following:

      • sudo less /var/log/nginx/error.log: checks the Nginx error logs.
      • sudo less /var/log/nginx/access.log: checks the Nginx access logs.
      • sudo journalctl -u nginx: checks the Nginx process logs.
      • sudo journalctl -u myproject: checks your Flask app’s uWSGI logs.

      Step 7 — Securing the Application

      To ensure that traffic to your server remains secure, obtain an SSL certificate for your domain. There are multiple ways to do this, including getting a free certificate from Let’s Encrypt, generating a self-signed certificate, or buying one from a commercial provider. For the sake of expediency, this tutorial explains how to obtain a free certificate from Let’s Encrypt.

      First, install Certbot and its Nginx plugin with apt:

      • sudo apt install certbot python3-certbot-nginx

      Certbot provides a variety of ways to obtain SSL certificates through plugins. The Nginx plugin will take care of reconfiguring Nginx and reloading the config whenever necessary. To use this plugin, type the following:

      • sudo certbot --nginx -d your_domain -d www.your_domain

      This runs certbot with the --nginx plugin, using -d to specify the names you’d like the certificate to be valid for.

      If this is your first time running certbot on this server, you will be prompted to enter an email address and agree to the terms of service. After doing so, certbot will communicate with the Let’s Encrypt server, then run a challenge to verify that you control the domain you’re requesting a certificate for.

      If that’s successful, certbot will ask how you’d like to configure your HTTPS settings:

      Output

      Please choose whether or not to redirect HTTP traffic to HTTPS, removing HTTP access. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1: No redirect - Make no further changes to the webserver configuration. 2: Redirect - Make all requests redirect to secure HTTPS access. Choose this for new sites, or if you're confident your site works on HTTPS. You can undo this change by editing your web server's configuration. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Select the appropriate number [1-2] then [enter] (press 'c' to cancel):

      Select your choice then hit ENTER. The configuration will be updated, and Nginx will reload to pick up the new settings. certbot will wrap up with a message telling you the process was successful and where your certificates are stored:

      Output

      IMPORTANT NOTES: - Congratulations! Your certificate and chain have been saved at: /etc/letsencrypt/live/your_domain/fullchain.pem Your key file has been saved at: /etc/letsencrypt/live/your_domain/privkey.pem Your cert will expire on 2020-08-18. To obtain a new or tweaked version of this certificate in the future, simply run certbot again with the "certonly" option. To non-interactively renew *all* of your certificates, run "certbot renew" - Your account credentials have been saved in your Certbot configuration directory at /etc/letsencrypt. You should make a secure backup of this folder now. This configuration directory will also contain certificates and private keys obtained by Certbot so making regular backups of this folder is ideal. - If you like Certbot, please consider supporting our work by: Donating to ISRG / Let's Encrypt: https://letsencrypt.org/donate Donating to EFF: https://eff.org/donate-le

      If you followed the Nginx installation instructions in the prerequisites, you will no longer need the redundant HTTP profile allowance:

      • sudo ufw delete allow 'Nginx HTTP'

      To verify the configuration, navigate once again to your domain, using https://:

      https://your_domain
      

      You will see your application output once again, along with your browser’s security indicator, which should indicate that the site is secured.

      Conclusion

      In this guide, you created and secured a basic Flask application within a Python virtual environment. Then you created a WSGI entry point so that any WSGI-capable application server can interface with it, and then configured the uWSGI app server to provide this function. Afterwards, you created a systemd service file to automatically launch the application server on boot. You also created an Nginx server block that passes web client traffic to the application server, thereby relaying external requests, and secured traffic to your server with Let’s Encrypt.

      Flask is a simple yet flexible framework meant to provide your applications with functionality without being too restrictive about structure or design. You can use the general stack described in this guide to serve the flask applications that you design.



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      How To Serve Flask Applications with Gunicorn and Nginx on Ubuntu 20.04


      In this guide, you will build a Python application using the Flask microframework on Ubuntu 20.04. The majority of this tutorial is about how to set up the Gunicorn application server to run the application and how to configure Nginx to act as a front-end reverse proxy.

      Introduction

      In this guide, you will build a Python application using the Flask microframework on Ubuntu 20.04. The bulk of this article will be about how to set up the Gunicorn application server and how to launch the application and configure Nginx to act as a front-end reverse proxy.

      Prerequisites

      Before starting this guide, you should have:

      • A server with Ubuntu 20.04 installed and a non-root user with sudo privileges. Follow our initial server setup guide for guidance.
      • Nginx installed, following Steps 1 and 2 of How To Install Nginx on Ubuntu 20.04.
      • A domain name configured to point to your server. You can purchase one on Namecheap or get one for free on Freenom. You can learn how to point domains to DigitalOcean by following the relevant documentation on domains and DNS. Be sure to create the following DNS records:

        • An A record with your_domain pointing to your server’s public IP address.
        • An A record with www.your_domain pointing to your server’s public IP address.
      • Familiarity with the WSGI specification, which the Gunicorn server will use to communicate with your Flask application. This discussion covers WSGI in more detail.

      Step 1 — Installing the Components from the Ubuntu Repositories

      Our first step will be to install all of the pieces we need from the Ubuntu repositories. This includes pip, the Python package manager, which will manage our Python components. We will also get the Python development files necessary to build some of the Gunicorn components.

      First, let’s update the local package index and install the packages that will allow us to build our Python environment. These will include python3-pip, along with a few more packages and development tools necessary for a robust programming environment:

      • sudo apt update
      • sudo apt install python3-pip python3-dev build-essential libssl-dev libffi-dev python3-setuptools

      With these packages in place, let’s move on to creating a virtual environment for our project.

      Step 2 — Creating a Python Virtual Environment

      Next, we’ll set up a virtual environment in order to isolate our Flask application from the other Python files on the system.

      Start by installing the python3-venv package, which will install the venv module:

      • sudo apt install python3-venv

      Next, let’s make a parent directory for our Flask project. Move into the directory after you create it:

      • mkdir ~/myproject
      • cd ~/myproject

      Create a virtual environment to store your Flask project’s Python requirements by typing:

      • python3 -m venv myprojectenv

      This will install a local copy of Python and pip into a directory called myprojectenv within your project directory.

      Before installing applications within the virtual environment, you need to activate it. Do so by typing:

      • source myprojectenv/bin/activate

      Your prompt will change to indicate that you are now operating within the virtual environment. It will look something like this: (myprojectenv)user@host:~/myproject$.

      Step 3 — Setting Up a Flask Application

      Now that you are in your virtual environment, you can install Flask and Gunicorn and get started on designing your application.

      First, let’s install wheel with the local instance of pip to ensure that our packages will install even if they are missing wheel archives:

      Note


      Regardless of which version of Python you are using, when the virtual environment is activated, you should use the pip command (not pip3).

      Next, let’s install Flask and Gunicorn:

      • pip install gunicorn flask

      Creating a Sample App

      Now that you have Flask available, you can create a simple application. Flask is a microframework. It does not include many of the tools that more full-featured frameworks might, and exists mainly as a module that you can import into your projects to assist you in initializing a web application.

      While your application might be more complex, we’ll create our Flask app in a single file, called myproject.py:

      • nano ~/myproject/myproject.py

      The application code will live in this file. It will import Flask and instantiate a Flask object. You can use this to define the functions that should be run when a specific route is requested:

      ~/myproject/myproject.py

      from flask import Flask
      app = Flask(__name__)
      
      @app.route("/")
      def hello():
          return "<h1 style="color:blue">Hello There!</h1>"
      
      if __name__ == "__main__":
          app.run(host="0.0.0.0")
      

      This basically defines what content to present when the root domain is accessed. Save and close the file when you’re finished.

      If you followed the initial server setup guide, you should have a UFW firewall enabled. To test the application, you need to allow access to port 5000:

      Now you can test your Flask app by typing:

      You will see output like the following, including a helpful warning reminding you not to use this server setup in production:

      Output

      * Serving Flask app "myproject" (lazy loading) * Environment: production WARNING: Do not use the development server in a production environment. Use a production WSGI server instead. * Debug mode: off * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)

      Visit your server’s IP address followed by :5000 in your web browser:

      http://your_server_ip:5000
      

      You should see something like this:

      Flask sample app

      When you are finished, hit CTRL-C in your terminal window to stop the Flask development server.

      Creating the WSGI Entry Point

      Next, let’s create a file that will serve as the entry point for our application. This will tell our Gunicorn server how to interact with the application.

      Let’s call the file wsgi.py:

      In this file, let’s import the Flask instance from our application and then run it:

      ~/myproject/wsgi.py

      from myproject import app
      
      if __name__ == "__main__":
          app.run()
      

      Save and close the file when you are finished.

      Step 4 — Configuring Gunicorn

      Your application is now written with an entry point established. We can now move on to configuring Gunicorn.

      Before moving on, we should check that Gunicorn can serve the application correctly.

      We can do this by simply passing it the name of our entry point. This is constructed as the name of the module (minus the .py extension), plus the name of the callable within the application. In our case, this is wsgi:app.

      We’ll also specify the interface and port to bind to so that the application will be started on a publicly available interface:

      • cd ~/myproject
      • gunicorn --bind 0.0.0.0:5000 wsgi:app

      You should see output like the following:

      Output

      [2020-05-20 14:13:00 +0000] [46419] [INFO] Starting gunicorn 20.0.4 [2020-05-20 14:13:00 +0000] [46419] [INFO] Listening at: http://0.0.0.0:5000 (46419) [2020-05-20 14:13:00 +0000] [46419] [INFO] Using worker: sync [2020-05-20 14:13:00 +0000] [46421] [INFO] Booting worker with pid: 46421

      Visit your server’s IP address with :5000 appended to the end in your web browser again:

      http://your_server_ip:5000
      

      You should see your application’s output:

      Flask sample app

      When you have confirmed that it’s functioning properly, press CTRL-C in your terminal window.

      We’re now done with our virtual environment, so we can deactivate it:

      Any Python commands will now use the system’s Python environment again.

      Next, let’s create the systemd service unit file. Creating a systemd unit file will allow Ubuntu’s init system to automatically start Gunicorn and serve the Flask application whenever the server boots.

      Create a unit file ending in .service within the /etc/systemd/system directory to begin:

      • sudo nano /etc/systemd/system/myproject.service

      Inside, we’ll start with the [Unit] section, which is used to specify metadata and dependencies. Let’s put a description of our service here and tell the init system to only start this after the networking target has been reached:

      /etc/systemd/system/myproject.service

      [Unit]
      Description=Gunicorn instance to serve myproject
      After=network.target
      

      Next, let’s open up the [Service] section. This will specify the user and group that we want the process to run under. Let’s give our regular user account ownership of the process since it owns all of the relevant files. Let’s also give group ownership to the www-data group so that Nginx can communicate easily with the Gunicorn processes. Remember to replace the username here with your username:

      /etc/systemd/system/myproject.service

      [Unit]
      Description=Gunicorn instance to serve myproject
      After=network.target
      
      [Service]
      User=sammy
      Group=www-data
      

      Next, let’s map out the working directory and set the PATH environmental variable so that the init system knows that the executables for the process are located within our virtual environment. Let’s also specify the command to start the service. This command will do the following:

      • Start 3 worker processes (though you should adjust this as necessary)
      • Create and bind to a Unix socket file, myproject.sock, within our project directory. We’ll set an umask value of 007 so that the socket file is created giving access to the owner and group, while restricting other access
      • Specify the WSGI entry point file name, along with the Python callable within that file (wsgi:app)

      Systemd requires that we give the full path to the Gunicorn executable, which is installed within our virtual environment.

      Remember to replace the username and project paths with your own information:

      /etc/systemd/system/myproject.service

      [Unit]
      Description=Gunicorn instance to serve myproject
      After=network.target
      
      [Service]
      User=sammy
      Group=www-data
      WorkingDirectory=/home/sammy/myproject
      Environment="PATH=/home/sammy/myproject/myprojectenv/bin"
      ExecStart=/home/sammy/myproject/myprojectenv/bin/gunicorn --workers 3 --bind unix:myproject.sock -m 007 wsgi:app
      

      Finally, let’s add an [Install] section. This will tell systemd what to link this service to if we enable it to start at boot. We want this service to start when the regular multi-user system is up and running:

      /etc/systemd/system/myproject.service

      [Unit]
      Description=Gunicorn instance to serve myproject
      After=network.target
      
      [Service]
      User=sammy
      Group=www-data
      WorkingDirectory=/home/sammy/myproject
      Environment="PATH=/home/sammy/myproject/myprojectenv/bin"
      ExecStart=/home/sammy/myproject/myprojectenv/bin/gunicorn --workers 3 --bind unix:myproject.sock -m 007 wsgi:app
      
      [Install]
      WantedBy=multi-user.target
      

      With that, our systemd service file is complete. Save and close it now.

      We can now start the Gunicorn service we created and enable it so that it starts at boot:

      • sudo systemctl start myproject
      • sudo systemctl enable myproject

      Let’s check the status:

      • sudo systemctl status myproject

      You should see output like this:

      Output

      ● myproject.service - Gunicorn instance to serve myproject Loaded: loaded (/etc/systemd/system/myproject.service; enabled; vendor preset: enabled) Active: active (running) since Wed 2020-05-20 14:15:18 UTC; 1s ago Main PID: 46430 (gunicorn) Tasks: 4 (limit: 2344) Memory: 51.3M CGroup: /system.slice/myproject.service ├─46430 /home/sammy/myproject/myprojectenv/bin/python3 /home/sammy/myproject/myprojectenv/bin/gunicorn --workers 3 --bind unix:myproject.sock -m 007 wsgi:app ├─46449 /home/sammy/myproject/myprojectenv/bin/python3 /home/sammy/myproject/myprojectenv/bin/gunicorn --workers 3 --bind unix:myproject.sock -m 007 wsgi:app ├─46450 /home/sammy/myproject/myprojectenv/bin/python3 /home/sammy/myproject/myprojectenv/bin/gunicorn --workers 3 --bind unix:myproject.sock -m 007 wsgi:app └─46451 /home/sammy/myproject/myprojectenv/bin/python3 /home/sammy/myproject/myprojectenv/bin/gunicorn --workers 3 --bind unix:myproject.sock -m 007 wsgi:app

      If you see any errors, be sure to resolve them before continuing with the tutorial.

      Step 5 — Configuring Nginx to Proxy Requests

      Our Gunicorn application server should now be up and running, waiting for requests on the socket file in the project directory. Let’s now configure Nginx to pass web requests to that socket by making some small additions to its configuration file.

      Begin by creating a new server block configuration file in Nginx’s sites-available directory. Let’s call this myproject to keep in line with the rest of the guide:

      • sudo nano /etc/nginx/sites-available/myproject

      Open up a server block and tell Nginx to listen on the default port 80. Let’s also tell it to use this block for requests for our server’s domain name:

      /etc/nginx/sites-available/myproject

      server {
          listen 80;
          server_name your_domain www.your_domain;
      }
      

      Next, let’s add a location block that matches every request. Within this block, we’ll include the proxy_params file that specifies some general proxying parameters that need to be set. We’ll then pass the requests to the socket we defined using the proxy_pass directive:

      /etc/nginx/sites-available/myproject

      server {
          listen 80;
          server_name your_domain www.your_domain;
      
          location / {
              include proxy_params;
              proxy_pass http://unix:/home/sammy/myproject/myproject.sock;
          }
      }
      

      Save and close the file when you’re finished.

      To enable the Nginx server block configuration you’ve just created, link the file to the sites-enabled directory:

      • sudo ln -s /etc/nginx/sites-available/myproject /etc/nginx/sites-enabled

      With the file in that directory, you can test for syntax errors:

      If this returns without indicating any issues, restart the Nginx process to read the new configuration:

      • sudo systemctl restart nginx

      Finally, let’s adjust the firewall again. We no longer need access through port 5000, so we can remove that rule. We can then allow full access to the Nginx server:

      • sudo ufw delete allow 5000
      • sudo ufw allow 'Nginx Full'

      You should now be able to navigate to your server’s domain name in your web browser:

      http://your_domain
      

      You should see your application’s output:

      Flask sample app

      If you encounter any errors, trying checking the following:

      • sudo less /var/log/nginx/error.log: checks the Nginx error logs.
      • sudo less /var/log/nginx/access.log: checks the Nginx access logs.
      • sudo journalctl -u nginx: checks the Nginx process logs.
      • sudo journalctl -u myproject: checks your Flask app’s Gunicorn logs.

      Step 6 — Securing the Application

      To ensure that traffic to your server remains secure, let’s get an SSL certificate for your domain. There are multiple ways to do this, including getting a free certificate from Let’s Encrypt, generating a self-signed certificate, or buying one from another provider and configuring Nginx to use it by following Steps 2 through 6 of How to Create a Self-signed SSL Certificate for Nginx in Ubuntu 20.04. We will go with option one for the sake of expediency.

      Install Certbot’s Nginx package with apt:

      • sudo apt install python3-certbot-nginx

      Certbot provides a variety of ways to obtain SSL certificates through plugins. The Nginx plugin will take care of reconfiguring Nginx and reloading the config whenever necessary. To use this plugin, type the following:

      • sudo certbot --nginx -d your_domain -d www.your_domain

      This runs certbot with the --nginx plugin, using -d to specify the names we’d like the certificate to be valid for.

      If this is your first time running certbot, you will be prompted to enter an email address and agree to the terms of service. After doing so, certbot will communicate with the Let’s Encrypt server, then run a challenge to verify that you control the domain you’re requesting a certificate for.

      If that’s successful, certbot will ask how you’d like to configure your HTTPS settings:

      Output

      Please choose whether or not to redirect HTTP traffic to HTTPS, removing HTTP access. ------------------------------------------------------------------------------- 1: No redirect - Make no further changes to the webserver configuration. 2: Redirect - Make all requests redirect to secure HTTPS access. Choose this for new sites, or if you're confident your site works on HTTPS. You can undo this change by editing your web server's configuration. ------------------------------------------------------------------------------- Select the appropriate number [1-2] then [enter] (press 'c' to cancel):

      Select your choice then hit ENTER. The configuration will be updated, and Nginx will reload to pick up the new settings. certbot will wrap up with a message telling you the process was successful and where your certificates are stored:

      Output

      IMPORTANT NOTES: - Congratulations! Your certificate and chain have been saved at: /etc/letsencrypt/live/your_domain/fullchain.pem Your key file has been saved at: /etc/letsencrypt/live/your_domain/privkey.pem Your cert will expire on 2020-08-18. To obtain a new or tweaked version of this certificate in the future, simply run certbot again with the "certonly" option. To non-interactively renew *all* of your certificates, run "certbot renew" - Your account credentials have been saved in your Certbot configuration directory at /etc/letsencrypt. You should make a secure backup of this folder now. This configuration directory will also contain certificates and private keys obtained by Certbot so making regular backups of this folder is ideal. - If you like Certbot, please consider supporting our work by: Donating to ISRG / Let's Encrypt: https://letsencrypt.org/donate Donating to EFF: https://eff.org/donate-le

      If you followed the Nginx installation instructions in the prerequisites, you will no longer need the redundant HTTP profile allowance:

      • sudo ufw delete allow 'Nginx HTTP'

      To verify the configuration, navigate once again to your domain, using https://:

      https://your_domain
      

      You should see your application output once again, along with your browser’s security indicator, which should indicate that the site is secured.

      Conclusion

      In this guide, you created and secured a simple Flask application within a Python virtual environment. You created a WSGI entry point so that any WSGI-capable application server can interface with it, and then configured the Gunicorn app server to provide this function. Afterwards, you created a systemd service file to automatically launch the application server on boot. You also created an Nginx server block that passes web client traffic to the application server, relaying external requests, and secured traffic to your server with Let’s Encrypt.

      Flask is a very simple, but extremely flexible framework meant to provide your applications with functionality without being too restrictive about structure and design. You can use the general stack described in this guide to serve the flask applications that you design.



      Source link

      How To Serve Flask Applications with Gunicorn and Nginx on Ubuntu 18.04


      Introdução

      Neste guia, você construirá um aplicativo Python usando o microframework Flask no Ubuntu 18.04. A maior parte deste artigo será sobre como configurar o servidor do aplicativo Gunicorn, como iniciar o aplicativo e configurar o Nginx para atuar como um proxy reverso no front-end.

      Pré-requisitos

      Antes de iniciar este guia, você deve ter:

      • Um servidor com o Ubuntu 18.04 instalado e um usuário não raiz com privilégios sudo. Siga nosso guia de configuração inicial do servidor para orientação.
      • O Nginx instalado, seguindo os Passos 1 e 2 de Como Instalar o Nginx no Ubuntu 18.04.
      • Um nome de domínio configurado para apontar para o seu servidor. Você pode comprar um no Namecheap ou obter um de graça no Freenom. Você pode aprender como apontar domínios para o DigitalOcean seguindo a relevante documentação para domínios e DNS. Certifique-se de criar os seguintes registros DNS:

        • Um registro com o your_domain <^>apontando para o endereço IP público do seu servidor.
        • Um registro A com www.your_domain apontando para o endereço IP público do seu servidor.
      • Familiarize-se com a especificação do WSGI, que o servidor do Gunicorn usará para se comunicar com seu aplicativo Flask. Esta discussãoaborda mais detalhadamente o WSGI.

      Passo 1 — Instalando os componentes dos repositórios do Ubuntu

      Nosso primeiro passo será instalar todas as partes que precisamos dos repositórios do Ubuntu. Isso inclui o pip, o gerenciador de pacotes Python que irá gerenciar nossos componentes Python. Também vamos obter os arquivos de desenvolvimento do Python necessários para construir alguns dos componentes do Gunicorn.

      Primeiramente, vamos atualizar o índice local de pacotes e instalar os pacotes que irão nos permitir construir nosso ambiente Python. Estes incluem o python3-pip, junto com alguns outros pacotes e ferramentas de desenvolvimento necessários para um ambiente de programação robusto:

      • sudo apt update
      • sudo apt install python3-pip python3-dev build-essential libssl-dev libffi-dev python3-setuptools

      Com esses pacotes instalados, vamos seguir em frente para criar um ambiente virtual para nosso projeto.

      Passo 2 — Criando um Ambiente Virtual em Python

      Em seguida, vamos configurar um ambiente virtual para isolar nosso aplicativo Flask dos outros arquivos Python no sistema.

      Inicie instalando o pacote python3-venv, que instalará o módulo venv:

      • sudo apt install python3-venv

      Em seguida, vamos fazer um diretório pai para nosso projeto Flask. Acesse o diretório após criá-lo:

      • mkdir ~/myproject
      • cd ~/myproject

      Crie um ambiente virtual para armazenar os requisitos Python do projeto Flask digitando:

      • python3.6 -m venv myprojectenv

      Isso instalará uma cópia local do Python e do pip para um diretório chamado myprojectenv dentro do diretório do seu projeto.

      Antes de instalar aplicativos no ambiente virtual, você precisa ativá-lo. Faça isso digitando:

      • source myprojectenv/bin/activate

      Seu prompt mudará para indicar que você agora está operando no ambiente virtual. Ele se parecerá com isso: (myprojectenv)user@host:~/myproject$.

      Passo 3 — Configurando um aplicativo Flask

      Agora que você está no seu ambiente virtual, instale o Flask e o Gunicorn e comece a projetar seu aplicativo.

      Primeiramente, vamos instalar o wheel com a instância local do pip para garantir que nossos pacotes sejam instalados mesmo se estiverem faltando arquivos wheel:

      Nota: Independentemente da versão do Python que você estiver usando, quando o ambiente virtual for ativado, você deve usar o comando pip (não o pip3).

      Em seguida, vamos instalar o Flask e o Gunicorn:

      • pip install gunicorn flask

      Criando um app de exemplo

      Agora que você tem o Flask disponível, você pode criar um aplicativo simples. O Flask é um microframework. Ele não inclui muitas das ferramentas que os frameworks mais completos talvez tenham. Ele existe, principalmente, como um módulo que você pode importar para seus projetos para ajudá-lo na inicialização de um aplicativo Web.

      Embora seu aplicativo possa ser mais complexo, vamos criar nosso app Flask em um único arquivo, chamado myproject.py:<^>

      • nano ~/myproject/myproject.py

      O código do aplicativo ficará neste arquivo. Ele importará o Flask e instanciará um objeto Flask. Você pode usar isto para definir as funções que devem ser executadas quando uma rota específica for solicitada:

      ~/myproject/myproject.py

      from flask import Flask
      app = Flask(__name__)
      
      @app.route("/")
      def hello():
          return "<h1 style='color:blue'>Hello There!</h1>"
      
      if __name__ == "__main__":
          app.run(host='0.0.0.0')
      

      Isso define basicamente qual conteúdo apresentar quando o domínio raiz for acessado. Salve e feche o arquivo quando você terminar.

      Se você seguiu o guia de configuração inicial do servidor, você deverá ter um firewall UFW ativado. Para testar o aplicativo, será necessário permitir o acesso à porta 5000:

      Agora é possível testar seu app Flask digitando:

      Você verá um resultado como o seguinte, incluindo um aviso útil lembrando para não usar essa configuração de servidor na produção:

      Output

      * Serving Flask app "myproject" (lazy loading) * Environment: production WARNING: Do not use the development server in a production environment. Use a production WSGI server instead. * Debug mode: off * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)

      Visite o endereço IP do seu servidor seguido de :5000 no seu navegador Web:

      http://your_server_ip:5000
      

      Você deve ver algo como isto:

      Flask sample app

      Quando terminar, tecle CTRL-C na janela do seu terminal para parar o servidor de desenvolvimento Flask.

      Criando o ponto de entrada da WSGI

      Em seguida, vamos criar um arquivo que servirá como o ponto de entrada para nosso aplicativo. Isso dirá ao nosso servidor do Gunicorn como interagir com o aplicativo.

      Vamos chamar o arquivo de wsgi.py:

      Neste arquivo, vamos importar a instância Flask do nosso aplicativo e então executá-lo:

      ~/myproject/wsgi.py

      from myproject import app
      
      if __name__ == "__main__":
          app.run()
      

      Salve e feche o arquivo quando você terminar.

      Passo 4 — Configurando o Gunicorn

      Seu aplicativo agora está gravado com um ponto de entrada estabelecido. Podemos agora seguir em frente para configurar o Gunicorn.

      Antes de continuar, devemos verificar se o Gunicorn pode atender o aplicativo corretamente.

      Podemos fazer essa verificação simplesmente passando o nome do nosso ponto de entrada para o Gunicorn. Criamos esse ponto de entrada como o nome do módulo (menos a extensão .py) mais o nome do objeto callable dentro do aplicativo. No nosso caso, trata-se do wsgi:app.

      Também vamos especificar a interface e a porta a vincular, de modo que o aplicativo seja iniciado em uma interface disponível publicamente:

      • cd ~/myproject
      • gunicorn --bind 0.0.0.0:5000 wsgi:app

      Deverá ver um resultado como o seguinte:

      Output

      [2018-07-13 19:35:13 +0000] [28217] [INFO] Starting gunicorn 19.9.0 [2018-07-13 19:35:13 +0000] [28217] [INFO] Listening at: http://0.0.0.0:5000 (28217) [2018-07-13 19:35:13 +0000] [28217] [INFO] Using worker: sync [2018-07-13 19:35:13 +0000] [28220] [INFO] Booting worker with pid: 28220

      Visite o endereço IP do seu servidor com :5000 anexado ao final no seu navegador Web novamente:

      http://your_server_ip:5000
      

      Você deve ver o resultado do seu aplicativo:

      Flask sample app

      Quando você tiver confirmado que ele está funcionando corretamente, pressione CTRL-C na janela do seu terminal.

      Acabamos agora o nosso ambiente virtual, para que possamos desativá-lo:

      Agora, qualquer comando Python voltará a usar o ambiente do sistema Python.

      Em seguida, vamos criar o arquivo da unidade de serviço systemd. Criar um arquivo de unidade systemd permitirá que o sistema init do Ubuntu inicie automaticamente o Gunicorn e atenda o aplicativo Flask sempre que o servidor inicializar.

      Crie um arquivo de unidade que termine com .service dentro do diretório /etc/systemd/system para começar:

      • sudo nano /etc/systemd/system/myproject.service

      Ali, vamos começar com a seção [Unit], que é usada para especificar os metadados e dependências. Vamos colocar uma descrição do nosso serviço aqui e dizer ao sistema init para iniciar isso somente após o objetivo da rede ter sido alcançado:

      /etc/systemd/system/myproject.service

      [Unit]
      Description=Gunicorn instance to serve myproject
      After=network.target
      

      Em seguida, vamos abrir a seção [Service]. Isso especificará o usuário e o grupo sob o qual que queremos que o processo seja executado. Vamos dar à nossa conta de usuário regular a propriedade sobre o processo, uma vez que ela possui todos os arquivos relevantes. Vamos também dar a propriedade sobre o grupo para o grupo www-data, de modo que o Nginx possa se comunicar facilmente com os processos do Gunicorn. Lembre-se de substituir o nome de usuário abaixo pelo seu nome de usuário:

      /etc/systemd/system/myproject.service

      [Unit]
      Description=Gunicorn instance to serve myproject
      After=network.target
      
      [Service]
      User=sammy
      Group=www-data
      

      Em seguida, vamos mapear o diretório de trabalho e definir a variável de ambiente PATH para que o sistema init saiba que os executáveis do processo estão localizados dentro do nosso ambiente virtual. Vamos também especificar o comando para iniciar o serviço. Este comando fará o seguinte:

      • Iniciar três processos de trabalho (embora deva ajustar isso conforme necessário)
      • Criar e vincular a um arquivo de socket Unix, myproject<^>.sock, dentro de nosso diretório de projeto. Vamos definir um valor de umask de 007 para que o arquivo socket seja criado dando acesso ao proprietário e ao grupo, ao mesmo tempo que restringe outros acessos
      • Especificar o nome do arquivo de ponto de entrada da WSGI, junto com o objeto callable do Python dentro daquele arquivo (wsgi:app)

      O systemd exige que seja dado o caminho completo para o executável do Gunicorn, que está instalado dentro do nosso ambiente virtual.

      Lembre-se de substituir o nome de usuário e os caminhos do projeto por seus próprios dados:

      /etc/systemd/system/myproject.service

      [Unit]
      Description=Gunicorn instance to serve myproject
      After=network.target
      
      [Service]
      User=sammy
      Group=www-data
      WorkingDirectory=/home/sammy/myproject
      Environment="PATH=/home/sammy/myproject/myprojectenv/bin"
      ExecStart=/home/sammy/myproject/myprojectenv/bin/gunicorn --workers 3 --bind unix:myproject.sock -m 007 wsgi:app
      

      Finalmente, vamos adicionar uma seção [Install]. Isso dirá ao systemd ao que vincular este serviço se nós o habilitarmos para iniciar na inicialização. Queremos que este serviço comece quando o sistema regular de vários usuários estiver funcionando:

      /etc/systemd/system/myproject.service

      [Unit]
      Description=Gunicorn instance to serve myproject
      After=network.target
      
      [Service]
      User=sammy
      Group=www-data
      WorkingDirectory=/home/sammy/myproject
      Environment="PATH=/home/sammy/myproject/myprojectenv/bin"
      ExecStart=/home/sammy/myproject/myprojectenv/bin/gunicorn --workers 3 --bind unix:myproject.sock -m 007 wsgi:app
      
      [Install]
      WantedBy=multi-user.target
      

      Com isso, nosso arquivo de serviço systemd está completo. Salve e feche-o agora.

      Podemos agora iniciar o serviço Gunicorn que criamos e habilitá-lo para que ele seja iniciado na inicialização:

      • sudo systemctl start myproject
      • sudo systemctl enable myproject

      Vamos verificar o status:

      • sudo systemctl status myproject

      Você deve ver um resultado como este:

      Output

      ● myproject.service - Gunicorn instance to serve myproject Loaded: loaded (/etc/systemd/system/myproject.service; enabled; vendor preset: enabled) Active: active (running) since Fri 2018-07-13 14:28:39 UTC; 46s ago Main PID: 28232 (gunicorn) Tasks: 4 (limit: 1153) CGroup: /system.slice/myproject.service ├─28232 /home/sammy/myproject/myprojectenv/bin/python3.6 /home/sammy/myproject/myprojectenv/bin/gunicorn --workers 3 --bind unix:myproject.sock -m 007 ├─28250 /home/sammy/myproject/myprojectenv/bin/python3.6 /home/sammy/myproject/myprojectenv/bin/gunicorn --workers 3 --bind unix:myproject.sock -m 007 ├─28251 /home/sammy/myproject/myprojectenv/bin/python3.6 /home/sammy/myproject/myprojectenv/bin/gunicorn --workers 3 --bind unix:myproject.sock -m 007 └─28252 /home/sammy/myproject/myprojectenv/bin/python3.6 /home/sammy/myproject/myprojectenv/bin/gunicorn --workers 3 --bind unix:myproject.sock -m 007

      Se encontrar erros, certifique-se de resolvê-los antes de continuar com o tutorial.

      Passo 5 — Configurando o Nginx para solicitações de proxy

      Nosso servidor do aplicativo Gunicorn deve estar funcionando agora, esperando pedidos no arquivo de socket no diretório do projeto. Vamos agora configurar o Nginx para passar pedidos Web para aquele socket, fazendo algumas pequenas adições ao seu arquivo de configuração.

      Comece criando um novo arquivo de configuração do bloco do servidor no diretório sites-available do Nginx. Vamos chamá-lo de myproject para mantê-lo alinhado com o resto do guia:

      • sudo nano /etc/nginx/sites-available/myproject

      Abra um bloco de servidor e diga ao Nginx para escutar na porta padrão 80. Vamos também dizer a ele para usar este bloco para pedidos para o nome de domínio do nosso servidor:

      /etc/nginx/sites-available/myproject

      server {
          listen 80;
          server_name your_domain www.your_domain;
      }
      

      Em seguida, vamos adicionar um bloco de localização que corresponda a cada pedido. Dentro deste bloco, vamos incluir o arquivo proxy_params que especifica alguns parâmetros gerais de proxy que precisam ser configurados. Vamos então passar os pedidos para o socket que definimos usando a diretriz proxy_pass:

      /etc/nginx/sites-available/myproject

      server {
          listen 80;
          server_name your_domain www.your_domain;
      
          location / {
              include proxy_params;
              proxy_pass http://unix:/home/sammy/myproject/myproject.sock;
          }
      }
      

      Salve e feche o arquivo quando terminar.

      Para habilitar a configuração do bloco do servidor Nginx que acabou de criar, vincule o arquivo ao diretório sites-enabled:

      • sudo ln -s /etc/nginx/sites-available/myproject /etc/nginx/sites-enabled

      Com o arquivo naquele diretório, você pode testar quanto a erros de sintaxe:

      Se retornar sem indicar quaisquer problemas, reinicie o processo Nginx para ler a nova configuração:

      • sudo systemctl restart nginx

      Finalmente, vamos ajustar o firewall novamente. Já não precisamos de acesso através da porta 5000, então podemos remover essa regra. Podemos então conceder acesso total ao servidor Nginx:

      • sudo ufw delete allow 5000
      • sudo ufw allow 'Nginx Full'

      Agora, você consegue navegar até o nome de domínio do seu servidor no seu navegador Web:

      http://your_domain
      

      Você deve ver o resultado do seu aplicativo:

      Flask sample app

      Caso encontre quaisquer erros, tente verificar o seguinte:

      • sudo less /var/log/nginx/error.log: verifica os registros de erros do Nginx.
      • sudo less /var/log/nginx/access.log: verifica os registros de acesso do Nginx.
      • sudo journalctl -u nginx: verifica os registros de processo do Nginx.
      • sudo journalctl -u myproject: verifica os registros do Gunicorn do seu app Flask.

      Passo 6 — Protegendo o aplicativo

      Para garantir que o tráfego para seu servidor permaneça protegido, vamos obter um certificado SSL para seu domínio. Há várias maneiras de fazer isso, incluindo a obtenção de um certificado gratuito do Let’s Encrypt, gerando um certificado autoassinado ou comprando algum de outro provedor e configurando o Nginx para usá-lo, seguindo os Passos 2 a 6 de Como criar um certificado SSL autoassinado para o Nginx no Ubuntu 18.04. Vamos escolher a opção um por questão de conveniência.

      Primeiramente, adicione o repositório de software Ubuntu do Certbot:

      • sudo add-apt-repository ppa:certbot/certbot

      Aperte ENTER para aceitar.

      Instale o pacote Nginx do Certbot com o apt:

      • sudo apt install python-certbot-nginx

      O Certbot oferece várias maneiras de obter certificados SSL através de plug-ins. O plug-in Nginx cuidará da reconfiguração do Nginx e recarregará a configuração sempre que necessário. Para usar este plug-in, digite o seguinte:

      • sudo certbot --nginx -d your_domain -d www.your_domain

      Esse comando executa o certbot com o plug-in --nginx, usando -d para especificar os nomes para os quais desejamos um certificado válido.

      Se essa é a primeira vez que você executa o certbot, você será solicitado a informar um endereço de e-mail e concordar com os termos de serviço. Após fazer isso, o certbot se comunicará com o servidor da Let’s Encrypt, executando posteriormente um desafio para verificar se você controla o domínio para o qual está solicitando um certificado.

      Se tudo correr bem, o certbot perguntará como você quer definir suas configurações de HTTPS:

      Output

      Please choose whether or not to redirect HTTP traffic to HTTPS, removing HTTP access. ------------------------------------------------------------------------------- 1: No redirect - Make no further changes to the webserver configuration. 2: Redirect - Make all requests redirect to secure HTTPS access. Choose this for new sites, or if you're confident your site works on HTTPS. You can undo this change by editing your web server's configuration. ------------------------------------------------------------------------------- Select the appropriate number [1-2] then [enter] (press 'c' to cancel):

      Select your choice then hit ​​​ENTER​​​​​. A configuração será atualizada e o Nginx recarregará para aplicar as novas configurações. O certbot será encerrado com uma mensagem informando que o processo foi concluído e onde os certificados estão armazenados:

      Output

      IMPORTANT NOTES: - Congratulations! Your certificate and chain have been saved at: /etc/letsencrypt/live/your_domain/fullchain.pem Your key file has been saved at: /etc/letsencrypt/live/your_domain/privkey.pem Your cert will expire on 2018-07-23. To obtain a new or tweaked version of this certificate in the future, simply run certbot again with the "certonly" option. To non-interactively renew *all* of your certificates, run "certbot renew" - Your account credentials have been saved in your Certbot configuration directory at /etc/letsencrypt. You should make a secure backup of this folder now. This configuration directory will also contain certificates and private keys obtained by Certbot so making regular backups of this folder is ideal. - If you like Certbot, please consider supporting our work by: Donating to ISRG / Let's Encrypt: https://letsencrypt.org/donate Donating to EFF: https://eff.org/donate-le

      Se seguiu as instruções de instalação do Nginx nos pré-requisitos, a permissão do perfil HTTP redundante não é mais necessária:

      • sudo ufw delete allow 'Nginx HTTP'

      Para verificar a configuração, navegue novamente para seu domínio, usando https://:

      https://your_domain
      

      Você deve ver novamente o resultado do seu aplicativo, junto com o indicador de segurança do seu navegador, o qual deve indicar que o site está protegido.

      Conclusão

      Neste guia, você criou e protegeu um aplicativo Flask simples em um ambiente virtual Python. Você criou um ponto de entrada da WSGI para que qualquer servidor de aplicativo compatível com a WSGI possa interagir com ela, e então configurou o servidor de app Gunicorn para fornecer essa função. Depois, criou um arquivo de serviço systemd para iniciar automaticamente o servidor do aplicativo na inicialização. Você também criou um bloco de servidor Nginx que passa o tráfego Web do cliente para o servidor do aplicativo - retransmitindo pedidos externos - e protegeu o tráfego para seu servidor com o Let’s Encrypt.

      O Flask é um framework muito simples - mas extremamente flexível, destinado a fornecer funcionalidade a seus aplicativos sem ser restritivo demais em termos de estrutura e design. Você pode usar a pilha geral descrita neste guia para atender os aplicativos flask que projetar.



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