How To Set Up an ASGI Django App with Postgres, Nginx, and Uvicorn on Ubuntu 20.04
How To Set Up an ASGI Django App with Postgres, Nginx, and Uvicorn on Ubuntu 20.04

Tutorial

How To Set Up an ASGI Django App with Postgres, Nginx, and Uvicorn on Ubuntu 20.04

NginxPythonPostgreSQLDjangoPython FrameworksDevelopmentDatabasesUbuntu 20.04

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 a more secure and powerful web server is required for anything production related.

The traditional way to deploy a Django app is with a Web Server Gateway Interface (WSGI). However, with the advent of Python 3 and the support of asynchronous execution, you can now execute your Python apps via asynchronous callables with an Asynchronous Server Gateway Interface (ASGI). A successor to WSGI, the ASGI specification in Python is a superset of WSGI and can be a drop-in replacement for WSGI.

Django allows for an “async outside, sync inside” mode that allows your code to be synchronous internally, while the ASGI server handles requests asynchronously. By allowing the webserver to have an asynchronous callable, it can handle multiple incoming and outgoing events for each application. The Django application is still synchronous internally to allow for backward compatibility and to avoid the complexity of parallel computing. This also means that your Django app requires no changes to switch from WSGI to ASGI.

In this guide, you will install and configure some components on Ubuntu 20.04 to support and serve Django applications. You’ll set up a PostgreSQL database instead of using the default SQLite database. You will configure the Gunicorn application server paired with Uvicorn, an ASGI implementation, to interface with your applications asynchronously. You will then set up Nginx to reverse proxy to Gunicorn, giving you access to its security and performance features to serve your apps.

Prerequisites

To complete this tutorial, you will need:

Step 1 — Installing the Packages from the Ubuntu Repositories

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

First, you’ll need to update the local apt package index and then download and install the packages. The packages you install depend on which version of Python your project will use.

Use the following command to install the necessary system packages:

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

This command will install the Python libraries for setting up a virtual environment, the Postgres database system and the libraries needed to interact with it, and the Nginx web server. Next, you’ll create the PostgreSQL database and user for your Django application.

Step 2 — Creating the PostgreSQL Database and User

In this step, you’ll create a database and database user for your Django application.

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

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

Log into an interactive Postgres session by typing:

  • sudo -u postgres psql

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

First, create a database for your project:

  • CREATE DATABASE myproject;

Note: Every Postgres statement must end with a semicolon. If you’re experiencing issues, make sure your commands end with a semicolon.

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

  • CREATE USER myprojectuser WITH PASSWORD 'password';

Afterward, you’ll modify a few of the connection parameters for the user you 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.

You will set the default encoding to UTF-8, which Django expects. You’ll also set the default transaction isolation scheme to “read committed”, which blocks reads from uncommitted transactions. Lastly, you’ll set the timezone. By default, the Django project 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, you can give your new user access to administer your new database:

  • GRANT ALL PRIVILEGES ON DATABASE myproject TO myprojectuser;

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

  • \q

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 you have a database, you can begin getting the rest of your project requirements ready. You will be installing your Python requirements within a virtual environment for easier management.

First, create and move into a directory where you can keep your project files:

  • mkdir ~/myprojectdir
  • cd ~/myprojectdir

Then use Python’s built-in virtual environment tool to create a new virtual environment.

  • python3 -m venv myprojectenv

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. You can use this to install and configure an isolated Python environment for your project.

Before you install the project’s Python requirements, you’ll 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$.

You will install Django in the virtual environment. Installing Django into an environment specific to your project will allow your projects and their requirements to be handled separately. With your virtual environment active, install Django, Gunicorn, Uvicorn, 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 uvicorn 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 the Python components installed, you can create the actual Django project files.

Creating the Django Project

Since you already have a project directory, you can 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 you are defining the directory explicitly instead of allowing Django to make decisions relative to your current directory:

  • django-admin startproject myproject ~/myprojectdir

At this point, your project directory (~/myprojectdir in this tutorial) 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, asgi.py, settings.py, urls.py, and wsgi.py files.
  • ~/myprojectdir/myprojectenv/: The virtual environment directory you created earlier.

Adjusting the Project Settings

After creating your project files, you’ll need to adjust some 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 that may be used to connect to the Django instance. Any incoming requests with a Host header 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 associated with your Django server. List each item in quotations with entries separated by a comma. To allow 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 how to do this:

Note: Be sure to include localhost as one of the options since you 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. You already created a PostgreSQL database for your project, so you need to adjust the settings.

Change the settings with your PostgreSQL database information. You’ll tell Django to use the psycopg2 adaptor you installed with pip. You 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/'
import os
STATIC_ROOT = os.path.join(BASE_DIR, 'static/')

Save and close the file when you are finished.

Completing Initial Project Setup

Now, you can migrate the initial database schema to your 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.

You can collect all of the static content into the directory location you 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. To test the development server, you’ll have to allow access to the port you’ll be using.

Create an exception for port 8000 by typing:

  • sudo ufw allow 8000

Finally, you can test out 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 receive 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

In this tutorial, you will be using Gunicorn paired with Uvicorn to deploy the application. Although Gunicorn is traditionally used to deploy WSGI applications, it also provides a pluggable interface to provide ASGI deployment. It does this by allowing you to consume a worker class exposed by the ASGI server (uvicorn). Because Gunicorn is a more mature product and offers more configurations than Uvicorn, the Uvicorn maintainers recommend using gunicorn with the uvicorn worker class as a fully featured server and process manager.

Before leaving the virtual environment, you’ll test Gunicorn to make sure that it can serve the application.

To use uvicorn workers with the gunicorn server, enter your project directory and use the following gunicorn command to load the project’s ASGI module:

  • cd ~/myprojectdir
  • gunicorn --bind 0.0.0.0:8000 myproject.asgi -w 4 -k uvicorn.workers.UvicornWorker

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: It is not required to use Gunicorn to run your ASGI application. To use only uvicorn, you would use the following command:

  • uvicorn myproject.asgi:application --host 0.0.0.0 --port 8080

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

If the Django welcome page still appears after starting these commands, this is confirmation that gunicorn served the page and is working as intended. By using the gunicorn command, you passed Gunicorn a module by specifying the relative directory path to Django’s asgi.py file, which is the entry point to your 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 ASGI specification, go to the official ASGI website.

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

You’ve now finished configuring your Django application. You can back out of the virtual environment by typing:

  • deactivate

The virtual environment indicator in your prompt will be removed.

Step 5 — Creating systemd Socket and Service Files for Gunicorn

In the previous section, you tested that Gunicorn can interact with the Django application. In this step, you’ll implement a more robust way of starting and stopping the application server by making 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, you’ll 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 exception for the extension:

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

Start with the [Unit] section, which is used to specify metadata and dependencies. You’ll put a description of your service here and tell the init system to start this only after the networking target has been reached. Because the service relies on the socket from the socket file, you’ll 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, open up the [Service] section. You’ll specify the user and group that you want the process to run under. You will give your regular user account ownership of the process since it owns all relevant files. You’ll give group ownership to the www-data group so that Nginx can communicate easily with Gunicorn.

You’ll then map out the working directory and specify the command to use to start the service. In this case, you’ll have to specify the full path to the Gunicorn executable, which is installed within the virtual environment. You will bind the process to the Unix socket you created within the /run directory so that the process can communicate with Nginx. You’ll log all data to standard output so that the journald process can collect the Gunicorn logs. You can also specify any optional Gunicorn tweaks here. Here’s an example of specifying three worker processes:

/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 - \
          -k uvicorn.workers.UvicornWorker \
          --workers 3 \
          --bind unix:/run/gunicorn.sock \
          myproject.asgi:application

Finally, you’ll add an [Install] section. This will tell systemd what to link this service to if you enable it to start at boot. You’ll 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 - \
          -k uvicorn.workers.UvicornWorker \
          --workers 3 \
          --bind unix:/run/gunicorn.sock \
          myproject.asgi:application

[Install]
WantedBy=multi-user.target

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

You 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

Now that you have made systemd service and socket files, you will confirm that the operation was successful by checking for the socket file.

Step 6 — Checking for the Gunicorn Socket File

In this step, you’ll check for the Gunicorn socket file. First, check the status of the process to find out whether it was able to start:

  • sudo systemctl status gunicorn.socket

The output will look similar to this:

Output
● gunicorn.socket - gunicorn socket Loaded: loaded (/etc/systemd/system/gunicorn.socket; enabled; vendor prese> Active: active (listening) since Fri 2020-06-26 17:53:10 UTC; 14s ago Triggers: ● gunicorn.service Listen: /run/gunicorn.sock (Stream) Tasks: 0 (limit: 1137) Memory: 0B CGroup: /system.slice/gunicorn.socket

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

  • file /run/gunicorn.sock
Output
/run/gunicorn.sock: socket

If the systemctl status command indicated an error occurred or if you do not find the gunicorn.sock file in the directory, this indicates that the Gunicorn socket was not 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

In this step, you’ll test the 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, you can send a connection to the socket through curl by typing:

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

You should receive 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 Thu 2021-06-10 21:03:29 UTC; 13s ago TriggeredBy: ● gunicorn.socket Main PID: 11682 (gunicorn) Tasks: 4 (limit: 4682) Memory: 98.5M CGroup: /system.slice/gunicorn.service ├─11682 /home/sammy/myprojectdir/myprojectenv/bin/python3 /home/sammy/myprojectdir/myprojectenv/bin/gunicorn --access-logfile - --workers 3 -k uvicorn.workers.UvicornWorker --bind unix:/run/gunicorn.sock myproject.asgi:application ├─11705 /home/sammy/myprojectdir/myprojectenv/bin/python3 /home/sammy/myprojectdir/myprojectenv/bin/gunicorn --access-logfile - --workers 3 -k uvicorn.workers.UvicornWorker --bind unix:/run/gunicorn.sock myproject.asgi:application ├─11707 /home/sammy/myprojectdir/myprojectenv/bin/python3 /home/sammy/myprojectdir/myprojectenv/bin/gunicorn --access-logfile - --workers 3 -k uvicorn.workers.UvicornWorker --bind unix:/run/gunicorn.sock myproject.asgi:application └─11708 /home/sammy/myprojectdir/myprojectenv/bin/python3 /home/sammy/myprojectdir/myprojectenv/bin/gunicorn --access-logfile - --workers 3 -k uvicorn.workers.UvicornWorker --bind unix:/run/gunicorn.sock myproject.asgi:application Jun 10 21:03:29 django gunicorn[11705]: [2021-06-10 21:03:29 +0000] [11705] [INFO] ASGI 'lifespan' protocol appears unsupported. Jun 10 21:03:29 django gunicorn[11705]: [2021-06-10 21:03:29 +0000] [11705] [INFO] Application startup complete. Jun 10 21:03:30 django gunicorn[11707]: [2021-06-10 21:03:30 +0000] [11707] [INFO] Started server process [11707] Jun 10 21:03:30 django gunicorn[11707]: [2021-06-10 21:03:30 +0000] [11707] [INFO] Waiting for application startup. Jun 10 21:03:30 django gunicorn[11707]: [2021-06-10 21:03:30 +0000] [11707] [INFO] ASGI 'lifespan' protocol appears unsupported. Jun 10 21:03:30 django gunicorn[11707]: [2021-06-10 21:03:30 +0000] [11707] [INFO] Application startup complete. Jun 10 21:03:30 django gunicorn[11708]: [2021-06-10 21:03:30 +0000] [11708] [INFO] Started server process [11708] Jun 10 21:03:30 django gunicorn[11708]: [2021-06-10 21:03:30 +0000] [11708] [INFO] Waiting for application startup. Jun 10 21:03:30 django gunicorn[11708]: [2021-06-10 21:03:30 +0000] [11708] [INFO] ASGI 'lifespan' protocol appears unsupported. Jun 10 21:03:30 django gunicorn[11708]: [2021-06-10 21:03:30 +0000] [11708] [INFO] Application startup complete.

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, you’ll need to configure Nginx to pass traffic to the process. In this step, you will set up Nginx in front of Gunicorn to take advantage of its high-performance connection handling mechanisms and its easy-to-implement security features.

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. You’ll start by specifying that this block should listen on the normal port 80 and that it should respond to the server’s domain name or IP address:

/etc/nginx/sites-available/myproject
server {
    listen 80;
    server_name server_domain_or_IP;
}

Next, tell Nginx to ignore any problems with finding a favicon. You will also tell it where to find the static assets that you collected in the ~/myprojectdir/static directory. All of these files have a standard URI prefix of “/static”, so you 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, create a location / {} block to match all other requests. Inside this location, you’ll include the standard proxy_params file included with the Nginx installation and then you’ll 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, you 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:

  • sudo nginx -t

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

  • sudo systemctl restart nginx

Finally, you’ll need to open the firewall to normal traffic on port 80. Since you no longer need access to the development server, you 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 the Django welcome page with the rocket image displayed.

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, is sent over the network in plain text.

If you have a domain name, the easiest way to 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 Ubuntu 20.04. Follow the procedure using the Nginx server block you created in this tutorial.

Step 9 — 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 receive 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 receive a new error message written to the log. If you look at the message, it should help you narrow down the problem.

You might receive the following message:

“`[secondary_label Output]
connect() to unix:/run/gunicorn.sock failed (2: No such file or directory)

Output
This indicates that Nginx could not 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](#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 uses 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 (/) and the gunicorn.sock file. You can review the permissions and ownership values of the socket file and each of its parent directories by passing the absolute path to the 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), you 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 receive from Django when attempting to access parts of the application in the web browser is:

“`[secondary_label Output]
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:

```command
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, you’ve set up an ASGI Django project in its own virtual environment. You’ve configured Gunicorn and Uvicorn to translate client requests asynchronously so that Django can handle them. Afterward, you set up Nginx to act as a reverse proxy to handle client connections and serve the correct project depending on the client request.

Django streamlines the process of creating projects and applications 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 serve the applications you create from a single server.

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