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


      Introduction

      In this guide, you will build a Python application using the Flask microframework on Ubuntu 18.04. 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 18.04 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 18.04.
      • 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:

      • python3.6 -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

      [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

      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 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

      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 18.04. We will go with option one for the sake of expediency.

      First, add the Certbot Ubuntu repository:

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

      You'll need to press ENTER to accept.

      Install Certbot's Nginx package with apt:

      • sudo apt install python-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 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

      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 Set Up Django with Postgres, Nginx, and Gunicorn on Debian 9


      Introduction

      Django is a powerful web framework that can help you get your Python application or website off the ground. Django includes a simplified development server for testing your code locally, but for anything even slightly production related, a more secure and powerful web server is required.

      In this guide, we will demonstrate how to install and configure some components on Debian 9 to support and serve Django applications. We will be setting up a PostgreSQL database instead of using the default SQLite database. We will configure the Gunicorn application server to interface with our applications. We will then set up Nginx to reverse proxy to Gunicorn, giving us access to its security and performance features to serve our apps.

      Prerequisites

      In order to complete this guide, you should have a fresh Debian 9 server instance with a basic firewall and a non-root user with sudo privileges configured. You can learn how to set this up by running through our initial server setup guide.

      We will be installing Django within a virtual environment. Installing Django into an environment specific to your project will allow your projects and their requirements to be handled separately.

      Once we have our database and application up and running, we will install and configure the Gunicorn application server. This will serve as an interface to our application, translating client requests from HTTP to Python calls that our application can process. We will then set up Nginx in front of Gunicorn to take advantage of its high performance connection handling mechanisms and its easy-to-implement security features.

      Let’s get started.

      Step 1 — Installing the Packages from the Debian Repositories

      To begin the process, we’ll download and install all of the items we need from the Debian repositories. We will use the Python package manager pip to install additional components a bit later.

      We need to update the local apt package index and then download and install the packages. The packages we install depend on which version of Python your project will use.

      If you are using Django with Python 3, type:

      • sudo apt update
      • sudo apt install python3-pip python3-dev libpq-dev postgresql postgresql-contrib nginx curl

      Django 1.11 is the last release of Django that will support Python 2. If you are starting new projects, it is strongly recommended that you choose Python 3. If you still need to use Python 2, type:

      • sudo apt update
      • sudo apt install python-pip python-dev libpq-dev postgresql postgresql-contrib nginx curl

      This will install pip, the Python development files needed to build Gunicorn later, the Postgres database system and the libraries needed to interact with it, and the Nginx web server.

      Step 2 — Creating the PostgreSQL Database and User

      We’re going to jump right in and create a database and database user for our Django application.

      By default, Postgres uses an authentication scheme called “peer authentication” for local connections. Basically, this means that if the user’s operating system username matches a valid Postgres username, that user can login with no further authentication.

      During the Postgres installation, an operating system user named postgres was created to correspond to the postgres PostgreSQL administrative user. We need to use this user to perform administrative tasks. We can use sudo and pass in the username with the -u option.

      Log into an interactive Postgres session by typing:

      You will be given a PostgreSQL prompt where we can set up our requirements.

      First, create a database for your project:

      • CREATE DATABASE myproject;

      Note: Every Postgres statement must end with a semi-colon, so make sure that your command ends with one if you are experiencing issues.

      Next, create a database user for our project. Make sure to select a secure password:

      • CREATE USER myprojectuser WITH PASSWORD 'password';

      Afterwards, we'll modify a few of the connection parameters for the user we just created. This will speed up database operations so that the correct values do not have to be queried and set each time a connection is established.

      We are setting the default encoding to UTF-8, which Django expects. We are also setting the default transaction isolation scheme to "read committed", which blocks reads from uncommitted transactions. Lastly, we are setting the timezone. By default, our Django projects will be set to use UTC. These are all recommendations from the Django project itself:

      • ALTER ROLE myprojectuser SET client_encoding TO 'utf8';
      • ALTER ROLE myprojectuser SET default_transaction_isolation TO 'read committed';
      • ALTER ROLE myprojectuser SET timezone TO 'UTC';

      Now, we can give our new user access to administer our new database:

      • GRANT ALL PRIVILEGES ON DATABASE myproject TO myprojectuser;

      When you are finished, exit out of the PostgreSQL prompt by typing:

      Postgres is now set up so that Django can connect to and manage its database information.

      Step 3 — Creating a Python Virtual Environment for your Project

      Now that we have our database, we can begin getting the rest of our project requirements ready. We will be installing our Python requirements within a virtual environment for easier management.

      To do this, we first need access to the virtualenv command. We can install this with pip.

      If you are using Python 3, upgrade pip and install the package by typing:

      • sudo -H pip3 install --upgrade pip
      • sudo -H pip3 install virtualenv

      If you are using Python 2, upgrade pip and install the package by typing:

      • sudo -H pip install --upgrade pip
      • sudo -H pip install virtualenv

      With virtualenv installed, we can start forming our project. Create and move into a directory where we can keep our project files:

      • mkdir ~/myprojectdir
      • cd ~/myprojectdir

      Within the project directory, create a Python virtual environment by typing:

      This will create a directory called myprojectenv within your myprojectdir directory. Inside, it will install a local version of Python and a local version of pip. We can use this to install and configure an isolated Python environment for our project.

      Before we install our project's Python requirements, we need to activate the virtual environment. You can do that by typing:

      • source myprojectenv/bin/activate

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

      With your virtual environment active, install Django, Gunicorn, and the psycopg2 PostgreSQL adaptor with the local instance of pip:

      Note: When the virtual environment is activated (when your prompt has (myprojectenv) preceding it), use pip instead of pip3, even if you are using Python 3. The virtual environment's copy of the tool is always named pip, regardless of the Python version.

      • pip install django gunicorn psycopg2-binary

      You should now have all of the software needed to start a Django project.

      Step 4 — Creating and Configuring a New Django Project

      With our Python components installed, we can create the actual Django project files.

      Creating the Django Project

      Since we already have a project directory, we will tell Django to install the files here. It will create a second level directory with the actual code, which is normal, and place a management script in this directory. The key to this is that we are defining the directory explicitly instead of allowing Django to make decisions relative to our current directory:

      • django-admin.py startproject myproject ~/myprojectdir

      At this point, your project directory (~/myprojectdir in our case) should have the following content:

      • ~/myprojectdir/manage.py: A Django project management script.
      • ~/myprojectdir/myproject/: The Django project package. This should contain the __init__.py, settings.py, urls.py, and wsgi.py files.
      • ~/myprojectdir/myprojectenv/: The virtual environment directory we created earlier.

      Adjusting the Project Settings

      The first thing we should do with our newly created project files is adjust the settings. Open the settings file in your text editor:

      • nano ~/myprojectdir/myproject/settings.py

      Start by locating the ALLOWED_HOSTS directive. This defines a list of the server's addresses or domain names may be used to connect to the Django instance. Any incoming requests with a Host header that is not in this list will raise an exception. Django requires that you set this to prevent a certain class of security vulnerability.

      In the square brackets, list the IP addresses or domain names that are associated with your Django server. Each item should be listed in quotations with entries separated by a comma. If you wish requests for an entire domain and any subdomains, prepend a period to the beginning of the entry. In the snippet below, there are a few commented out examples used to demonstrate:

      Note: Be sure to include localhost as one of the options since we will be proxying connections through a local Nginx instance.

      ~/myprojectdir/myproject/settings.py

      . . .
      # The simplest case: just add the domain name(s) and IP addresses of your Django server
      # ALLOWED_HOSTS = [ 'example.com', '203.0.113.5']
      # To respond to 'example.com' and any subdomains, start the domain with a dot
      # ALLOWED_HOSTS = ['.example.com', '203.0.113.5']
      ALLOWED_HOSTS = ['your_server_domain_or_IP', 'second_domain_or_IP', . . ., 'localhost']
      

      Next, find the section that configures database access. It will start with DATABASES. The configuration in the file is for a SQLite database. We already created a PostgreSQL database for our project, so we need to adjust the settings.

      Change the settings with your PostgreSQL database information. We tell Django to use the psycopg2 adaptor we installed with pip. We need to give the database name, the database username, the database user's password, and then specify that the database is located on the local computer. You can leave the PORT setting as an empty string:

      ~/myprojectdir/myproject/settings.py

      . . .
      
      DATABASES = {
          'default': {
              'ENGINE': 'django.db.backends.postgresql_psycopg2',
              'NAME': 'myproject',
              'USER': 'myprojectuser',
              'PASSWORD': 'password',
              'HOST': 'localhost',
              'PORT': '',
          }
      }
      
      . . .
      

      Next, move down to the bottom of the file and add a setting indicating where the static files should be placed. This is necessary so that Nginx can handle requests for these items. The following line tells Django to place them in a directory called static in the base project directory:

      ~/myprojectdir/myproject/settings.py

      . . .
      
      STATIC_URL = '/static/'
      STATIC_ROOT = os.path.join(BASE_DIR, 'static/')
      

      Save and close the file when you are finished.

      Completing Initial Project Setup

      Now, we can migrate the initial database schema to our PostgreSQL database using the management script:

      • ~/myprojectdir/manage.py makemigrations
      • ~/myprojectdir/manage.py migrate

      Create an administrative user for the project by typing:

      • ~/myprojectdir/manage.py createsuperuser

      You will have to select a username, provide an email address, and choose and confirm a password.

      We can collect all of the static content into the directory location we configured by typing:

      • ~/myprojectdir/manage.py collectstatic

      You will have to confirm the operation. The static files will then be placed in a directory called static within your project directory.

      If you followed the initial server setup guide, you should have a UFW firewall protecting your server. In order to test the development server, we'll have to allow access to the port we'll be using.

      Create an exception for port 8000 by typing:

      Finally, you can test our your project by starting up the Django development server with this command:

      • ~/myprojectdir/manage.py runserver 0.0.0.0:8000

      In your web browser, visit your server's domain name or IP address followed by :8000:

      http://server_domain_or_IP:8000
      

      You should see the default Django index page:

      Django index page

      If you append /admin to the end of the URL in the address bar, you will be prompted for the administrative username and password you created with the createsuperuser command:

      Django admin login

      After authenticating, you can access the default Django admin interface:

      Django admin interface

      When you are finished exploring, hit CTRL-C in the terminal window to shut down the development server.

      Testing Gunicorn's Ability to Serve the Project

      The last thing we want to do before leaving our virtual environment is test Gunicorn to make sure that it can serve the application. We can do this by entering our project directory and using gunicorn to load the project's WSGI module:

      • cd ~/myprojectdir
      • gunicorn --bind 0.0.0.0:8000 myproject.wsgi

      This will start Gunicorn on the same interface that the Django development server was running on. You can go back and test the app again.

      Note: The admin interface will not have any of the styling applied since Gunicorn does not know how to find the static CSS content responsible for this.

      We passed Gunicorn a module by specifying the relative directory path to Django's wsgi.py file, which is the entry point to our application, using Python's module syntax. Inside of this file, a function called application is defined, which is used to communicate with the application. To learn more about the WSGI specification, click here.

      When you are finished testing, hit CTRL-C in the terminal window to stop Gunicorn.

      We're now finished configuring our Django application. We can back out of our virtual environment by typing:

      The virtual environment indicator in your prompt will be removed.

      Step 5 — Creating systemd Socket and Service Files for Gunicorn

      We have tested that Gunicorn can interact with our Django application, but we should implement a more robust way of starting and stopping the application server. To accomplish this, we'll make systemd service and socket files.

      The Gunicorn socket will be created at boot and will listen for connections. When a connection occurs, systemd will automatically start the Gunicorn process to handle the connection.

      Start by creating and opening a systemd socket file for Gunicorn with sudo privileges:

      • sudo nano /etc/systemd/system/gunicorn.socket

      Inside, we will create a [Unit] section to describe the socket, a [Socket] section to define the socket location, and an [Install] section to make sure the socket is created at the right time:

      /etc/systemd/system/gunicorn.socket

      [Unit]
      Description=gunicorn socket
      
      [Socket]
      ListenStream=/run/gunicorn.sock
      
      [Install]
      WantedBy=sockets.target
      

      Save and close the file when you are finished.

      Next, create and open a systemd service file for Gunicorn with sudo privileges in your text editor. The service filename should match the socket filename with the exception of the extension:

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

      Start with the [Unit] section, which is used to specify metadata and dependencies. We'll put a description of our service here and tell the init system to only start this after the networking target has been reached. Because our service relies on the socket from the socket file, we need to include a Requires directive to indicate that relationship:

      /etc/systemd/system/gunicorn.service

      [Unit]
      Description=gunicorn daemon
      Requires=gunicorn.socket
      After=network.target
      

      Next, we'll open up the [Service] section. We'll specify the user and group that we want to process to run under. We will give our regular user account ownership of the process since it owns all of the relevant files. We'll give group ownership to the www-data group so that Nginx can communicate easily with Gunicorn.

      We'll then map out the working directory and specify the command to use to start the service. In this case, we'll have to specify the full path to the Gunicorn executable, which is installed within our virtual environment. We will bind the process to the Unix socket we created within the /run directory so that the process can communicate with Nginx. We log all data to standard output so that the journald process can collect the Gunicorn logs. We can also specify any optional Gunicorn tweaks here. For example, we specified 3 worker processes in this case:

      /etc/systemd/system/gunicorn.service

      [Unit]
      Description=gunicorn daemon
      Requires=gunicorn.socket
      After=network.target
      
      [Service]
      User=sammy
      Group=www-data
      WorkingDirectory=/home/sammy/myprojectdir
      ExecStart=/home/sammy/myprojectdir/myprojectenv/bin/gunicorn 
                --access-logfile - 
                --workers 3 
                --bind unix:/run/gunicorn.sock 
                myproject.wsgi:application
      

      Finally, we'll 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/gunicorn.service

      [Unit]
      Description=gunicorn daemon
      Requires=gunicorn.socket
      After=network.target
      
      [Service]
      User=sammy
      Group=www-data
      WorkingDirectory=/home/sammy/myprojectdir
      ExecStart=/home/sammy/myprojectdir/myprojectenv/bin/gunicorn 
                --access-logfile - 
                --workers 3 
                --bind unix:/run/gunicorn.sock 
                myproject.wsgi:application
      
      [Install]
      WantedBy=multi-user.target
      

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

      We can now start and enable the Gunicorn socket. This will create the socket file at /run/gunicorn.sock now and at boot. When a connection is made to that socket, systemd will automatically start the gunicorn.service to handle it:

      • sudo systemctl start gunicorn.socket
      • sudo systemctl enable gunicorn.socket

      We can confirm that the operation was successful by checking for the socket file.

      Step 6 — Checking for the Gunicorn Socket File

      Check the status of the process to find out whether it was able to start:

      • sudo systemctl status gunicorn.socket

      Next, check for the existence of the gunicorn.sock file within the /run directory:

      Output

      /run/gunicorn.sock: socket

      If the systemctl status command indicated that an error occurred or if you do not find the gunicorn.sock file in the directory, it's an indication that the Gunicorn socket was not able to be created correctly. Check the Gunicorn socket's logs by typing:

      • sudo journalctl -u gunicorn.socket

      Take another look at your /etc/systemd/system/gunicorn.socket file to fix any problems before continuing.

      Step 7 — Testing Socket Activation

      Currently, if you've only started the gunicorn.socket unit, the gunicorn.service will not be active yet since the socket has not yet received any connections. You can check this by typing:

      • sudo systemctl status gunicorn

      Output

      ● gunicorn.service - gunicorn daemon Loaded: loaded (/etc/systemd/system/gunicorn.service; disabled; vendor preset: enabled) Active: inactive (dead)

      To test the socket activation mechanism, we can send a connection to the socket through curl by typing:

      • curl --unix-socket /run/gunicorn.sock localhost

      You should see the HTML output from your application in the terminal. This indicates that Gunicorn was started and was able to serve your Django application. You can verify that the Gunicorn service is running by typing:

      • sudo systemctl status gunicorn

      Output

      ● gunicorn.service - gunicorn daemon Loaded: loaded (/etc/systemd/system/gunicorn.service; disabled; vendor preset: enabled) Active: active (running) since Mon 2018-07-09 20:00:40 UTC; 4s ago Main PID: 1157 (gunicorn) Tasks: 4 (limit: 1153) CGroup: /system.slice/gunicorn.service ├─1157 /home/sammy/myprojectdir/myprojectenv/bin/python3 /home/sammy/myprojectdir/myprojectenv/bin/gunicorn --access-logfile - --workers 3 --bind unix:/run/gunicorn.sock myproject.wsgi:application ├─1178 /home/sammy/myprojectdir/myprojectenv/bin/python3 /home/sammy/myprojectdir/myprojectenv/bin/gunicorn --access-logfile - --workers 3 --bind unix:/run/gunicorn.sock myproject.wsgi:application ├─1180 /home/sammy/myprojectdir/myprojectenv/bin/python3 /home/sammy/myprojectdir/myprojectenv/bin/gunicorn --access-logfile - --workers 3 --bind unix:/run/gunicorn.sock myproject.wsgi:application └─1181 /home/sammy/myprojectdir/myprojectenv/bin/python3 /home/sammy/myprojectdir/myprojectenv/bin/gunicorn --access-logfile - --workers 3 --bind unix:/run/gunicorn.sock myproject.wsgi:application Jul 09 20:00:40 django1 systemd[1]: Started gunicorn daemon. Jul 09 20:00:40 django1 gunicorn[1157]: [2018-07-09 20:00:40 +0000] [1157] [INFO] Starting gunicorn 19.9.0 Jul 09 20:00:40 django1 gunicorn[1157]: [2018-07-09 20:00:40 +0000] [1157] [INFO] Listening at: unix:/run/gunicorn.sock (1157) Jul 09 20:00:40 django1 gunicorn[1157]: [2018-07-09 20:00:40 +0000] [1157] [INFO] Using worker: sync Jul 09 20:00:40 django1 gunicorn[1157]: [2018-07-09 20:00:40 +0000] [1178] [INFO] Booting worker with pid: 1178 Jul 09 20:00:40 django1 gunicorn[1157]: [2018-07-09 20:00:40 +0000] [1180] [INFO] Booting worker with pid: 1180 Jul 09 20:00:40 django1 gunicorn[1157]: [2018-07-09 20:00:40 +0000] [1181] [INFO] Booting worker with pid: 1181 Jul 09 20:00:41 django1 gunicorn[1157]: - - [09/Jul/2018:20:00:41 +0000] "GET / HTTP/1.1" 200 16348 "-" "curl/7.58.0"

      If the output from curl or the output of systemctl status indicates that a problem occurred, check the logs for additional details:

      • sudo journalctl -u gunicorn

      Check your /etc/systemd/system/gunicorn.service file for problems. If you make changes to the /etc/systemd/system/gunicorn.service file, reload the daemon to reread the service definition and restart the Gunicorn process by typing:

      • sudo systemctl daemon-reload
      • sudo systemctl restart gunicorn

      Make sure you troubleshoot the above issues before continuing.

      Step 8 — Configure Nginx to Proxy Pass to Gunicorn

      Now that Gunicorn is set up, we need to configure Nginx to pass traffic to the process.

      Start by creating and opening a new server block in Nginx's sites-available directory:

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

      Inside, open up a new server block. We will start by specifying that this block should listen on the normal port 80 and that it should respond to our server's domain name or IP address:

      /etc/nginx/sites-available/myproject

      server {
          listen 80;
          server_name server_domain_or_IP;
      }
      

      Next, we will tell Nginx to ignore any problems with finding a favicon. We will also tell it where to find the static assets that we collected in our ~/myprojectdir/static directory. All of these files have a standard URI prefix of "/static", so we can create a location block to match those requests:

      /etc/nginx/sites-available/myproject

      server {
          listen 80;
          server_name server_domain_or_IP;
      
          location = /favicon.ico { access_log off; log_not_found off; }
          location /static/ {
              root /home/sammy/myprojectdir;
          }
      }
      

      Finally, we'll create a location / {} block to match all other requests. Inside of this location, we'll include the standard proxy_params file included with the Nginx installation and then we will pass the traffic directly to the Gunicorn socket:

      /etc/nginx/sites-available/myproject

      server {
          listen 80;
          server_name server_domain_or_IP;
      
          location = /favicon.ico { access_log off; log_not_found off; }
          location /static/ {
              root /home/sammy/myprojectdir;
          }
      
          location / {
              include proxy_params;
              proxy_pass http://unix:/run/gunicorn.sock;
          }
      }
      

      Save and close the file when you are finished. Now, we can enable the file by linking it to the sites-enabled directory:

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

      Test your Nginx configuration for syntax errors by typing:

      If no errors are reported, go ahead and restart Nginx by typing:

      • sudo systemctl restart nginx

      Finally, we need to open up our firewall to normal traffic on port 80. Since we no longer need access to the development server, we can remove the rule to open port 8000 as well:

      • sudo ufw delete allow 8000
      • sudo ufw allow 'Nginx Full'

      You should now be able to go to your server's domain or IP address to view your application.

      Note: After configuring Nginx, the next step should be securing traffic to the server using SSL/TLS. This is important because without it, all information, including passwords are sent over the network in plain text.

      If you have a domain name, the easiest way get an SSL certificate to secure your traffic is using Let's Encrypt. Follow this guide to set up Let's Encrypt with Nginx on Debian 9. Follow the procedure using the Nginx server block we created in this guide.

      If you do not have a domain name, you can still secure your site for testing and learning with a self-signed SSL certificate. Again, follow the process using the Nginx server block we created in this tutorial.

      Troubleshooting Nginx and Gunicorn

      If this last step does not show your application, you will need to troubleshoot your installation.

      Nginx Is Showing the Default Page Instead of the Django Application

      If Nginx displays the default page instead of proxying to your application, it usually means that you need to adjust the server_name within the /etc/nginx/sites-available/myproject file to point to your server's IP address or domain name.

      Nginx uses the server_name to determine which server block to use to respond to requests. If you are seeing the default Nginx page, it is a sign that Nginx wasn't able to match the request to a sever block explicitly, so it's falling back on the default block defined in /etc/nginx/sites-available/default.

      The server_name in your project's server block must be more specific than the one in the default server block to be selected.

      Nginx Is Displaying a 502 Bad Gateway Error Instead of the Django Application

      A 502 error indicates that Nginx is unable to successfully proxy the request. A wide range of configuration problems express themselves with a 502 error, so more information is required to troubleshoot properly.

      The primary place to look for more information is in Nginx's error logs. Generally, this will tell you what conditions caused problems during the proxying event. Follow the Nginx error logs by typing:

      • sudo tail -F /var/log/nginx/error.log

      Now, make another request in your browser to generate a fresh error (try refreshing the page). You should see a fresh error message written to the log. If you look at the message, it should help you narrow down the problem.

      You might see some of the following message:

      connect() to unix:/run/gunicorn.sock failed (2: No such file or directory)

      This indicates that Nginx was unable to find the gunicorn.sock file at the given location. You should compare the proxy_pass location defined within /etc/nginx/sites-available/myproject file to the actual location of the gunicorn.sock file generated by the gunicorn.socket systemd unit.

      If you cannot find a gunicorn.sock file within the /run directory, it generally means that the systemd socket file was unable to create it. Go back to the section on checking for the Gunicorn socket file to step through the troubleshooting steps for Gunicorn.

      connect() to unix:/run/gunicorn.sock failed (13: Permission denied)

      This indicates that Nginx was unable to connect to the Gunicorn socket because of permissions problems. This can happen when the procedure is followed using the root user instead of a sudo user. While systemd is able to create the Gunicorn socket file, Nginx is unable to access it.

      This can happen if there are limited permissions at any point between the root directory (/) the gunicorn.sock file. We can see the permissions and ownership values of the socket file and each of its parent directories by passing the absolute path to our socket file to the namei command:

      • namei -l /run/gunicorn.sock

      Output

      f: /run/gunicorn.sock drwxr-xr-x root root / drwxr-xr-x root root run srw-rw-rw- root root gunicorn.sock

      The output displays the permissions of each of the directory components. By looking at the permissions (first column), owner (second column) and group owner (third column), we can figure out what type of access is allowed to the socket file.

      In the above example, the socket file and each of the directories leading up to the socket file have world read and execute permissions (the permissions column for the directories end with r-x instead of ---). The Nginx process should be able to access the socket successfully.

      If any of the directories leading up to the socket do not have world read and execute permission, Nginx will not be able to access the socket without allowing world read and execute permissions or making sure group ownership is given to a group that Nginx is a part of.

      Django Is Displaying: "could not connect to server: Connection refused"

      One message that you may see from Django when attempting to access parts of the application in the web browser is:

      OperationalError at /admin/login/
      could not connect to server: Connection refused
          Is the server running on host "localhost" (127.0.0.1) and accepting
          TCP/IP connections on port 5432?
      

      This indicates that Django is unable to connect to the Postgres database. Make sure that the Postgres instance is running by typing:

      • sudo systemctl status postgresql

      If it is not, you can start it and enable it to start automatically at boot (if it is not already configured to do so) by typing:

      • sudo systemctl start postgresql
      • sudo systemctl enable postgresql

      If you are still having issues, make sure the database settings defined in the ~/myprojectdir/myproject/settings.py file are correct.

      Further Troubleshooting

      For additional troubleshooting, the logs can help narrow down root causes. Check each of them in turn and look for messages indicating problem areas.

      The following logs may be helpful:

      • Check the Nginx process logs by typing: sudo journalctl -u nginx
      • Check the Nginx access logs by typing: sudo less /var/log/nginx/access.log
      • Check the Nginx error logs by typing: sudo less /var/log/nginx/error.log
      • Check the Gunicorn application logs by typing: sudo journalctl -u gunicorn
      • Check the Gunicorn socket logs by typing: sudo journalctl -u gunicorn.socket

      As you update your configuration or application, you will likely need to restart the processes to adjust to your changes.

      If you update your Django application, you can restart the Gunicorn process to pick up the changes by typing:

      • sudo systemctl restart gunicorn

      If you change Gunicorn socket or service files, reload the daemon and restart the process by typing:

      • sudo systemctl daemon-reload
      • sudo systemctl restart gunicorn.socket gunicorn.service

      If you change the Nginx server block configuration, test the configuration and then Nginx by typing:

      • sudo nginx -t && sudo systemctl restart nginx

      These commands are helpful for picking up changes as you adjust your configuration.

      Conclusion

      In this guide, we've set up a Django project in its own virtual environment. We've configured Gunicorn to translate client requests so that Django can handle them. Afterwards, we set up Nginx to act as a reverse proxy to handle client connections and serve the correct project depending on the client request.

      Django makes creating projects and applications simple by providing many of the common pieces, allowing you to focus on the unique elements. By leveraging the general tool chain described in this article, you can easily serve the applications you create from a single server.



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