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lnls/uwsgi-nginx-flask

By lnls

•Updated over 7 years ago

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lnls/uwsgi-nginx-flask repository overview

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⁠uwsgi-nginx-flask

Docker image with uWSGI and Nginx for Flask web applications in Python 3.7, Python 3.6, Python 3.5 and Python 2.7 running in a single container. Optionally using Alpine Linux.

⁠Description

This Docker⁠ image allows you to create Flask⁠ web applications in Python⁠ that run with uWSGI⁠ and Nginx⁠ in a single container.

The combination of uWSGI with Nginx is a common way to deploy Python Flask web applications⁠. It is widely used in the industry and would give you decent performance. (*)

There is also an Alpine version. If you want it, use one of the Alpine tags from above.

⁠* Note on performance and features

If you are starting a new project, you might benefit from a newer and faster framework based on ASGI instead of WSGI (Flask and Django are WSGI-based).

You could use an ASGI framework like:

FastAPI, or Starlette, would give you about 800% (8x) the performance achievable with Flask using this image (tiangolo/uwsgi-nginx-flask). You can see the third-party benchmarks here⁠.

Also, if you want to use new technologies like WebSockets it would be easier (and possible) with a newer framework based on ASGI, like FastAPI or Starlette. As the standard ASGI was designed to be able to handle asynchronous code like the one needed for WebSockets.

⁠If you need Flask

If you need to use Flask (instead of something based on ASGI) and you need to have the best performance possible, you can use the alternative image: tiangolo/meinheld-gunicorn-flask⁠.

tiangolo/meinheld-gunicorn-flask will give you about 400% (4x) the performance of this image (tiangolo/uwsgi-nginx-flask).

It is very simlar to tiangolo/uwsgi-nginx-flask, so you can still use many of the ideas described here.

GitHub repo: https://github.com/tiangolo/uwsgi-nginx-flask-docker⁠

Docker Hub image: https://hub.docker.com/r/tiangolo/uwsgi-nginx-flask/⁠

⁠Examples (simple project templates)

  • python3.7 tag: general Flask web application:

example-flask-python3.7.zip⁠

  • python3.7 tag: general Flask web application, structured as a package, for bigger Flask projects, with different submodules. Use it only as an example of how to import your modules and how to structure your own project:

example-flask-package-python3.7.zip⁠

  • python3.7 tag: static/index.html served directly in /, e.g. for Vue⁠, React⁠, Angular⁠, or any other Single-Page Application that uses a static index.html, not modified by Python:

example-flask-python3.7-index.zip⁠

⁠General Instructions

You don't have to clone this repo, you should be able to use this image as a base image for your project with something in your Dockerfile like:

FROM tiangolo/uwsgi-nginx-flask:python3.7

COPY ./app /app

There are several image tags available for Python 3.7, Python 3.6, Python 3.5 and Python 2.7, but for new projects you should use Python 3.7.

As of now, everyone⁠ should be⁠ using Python 3⁠.

There are several template projects that you can download (as a .zip file) to bootstrap your project in the section "Examples (project templates)" above.

This Docker image is based on tiangolo/uwsgi-nginx⁠. That Docker image has uWSGI and Nginx installed in the same container and was made to be the base of this image.

⁠Quick Start

Note: You can download the example-flask-python3.7.zip project example and use it as the template for your project from the section Examples above.

Or you may follow the instructions to build your project from scratch:

  • Go to your project directory
  • Create a Dockerfile with:
FROM tiangolo/uwsgi-nginx-flask:python3.7

COPY ./app /app
  • Create an app directory and enter in it
  • Create a main.py file (it should be named like that and should be in your app directory) with:
from flask import Flask
app = Flask(__name__)

@app.route("/")
def hello():
    return "Hello World from Flask"

if __name__ == "__main__":
    # Only for debugging while developing
    app.run(host='0.0.0.0', debug=True, port=80)

the main application object should be named app (in the code) as in this example.

Note: The section with the main() function is for debugging purposes. To learn more, read the Advanced instructions below.

  • You should now have a directory structure like:
.
├── app
│   └── main.py
└── Dockerfile
  • Go to the project directory (in where your Dockerfile is, containing your app directory)
  • Build your Flask image:
docker build -t myimage .
  • Run a container based on your image:
docker run -d --name mycontainer -p 80:80 myimage

...and you have an optimized Flask server in a Docker container.

You should be able to check it in your Docker container's URL, for example: http://192.168.99.100⁠ or http://127.0.0.1⁠

⁠Project Generators

There are several project generators that you can use to start your project, with everything already configured.

⁠Server set up

All these project generators include automatic and free HTTPS certificates generation provided by:

...using the ideas from DockerSwarm.rocks⁠.

It would take about 20 minutes to read that guide and have a Docker cluster (of one or more servers) up and running ready for your projects.

You can have several projects in the same cluster, all with automatic HTTPS, even if they have different domains or sub-domains.

⁠Generate a project

Then you can use one of the following project generators.

It would take about 5 extra minutes to generate one of these projects.

⁠Deploy

And it would take about 3 more minutes to deploy them in your cluster.

In total, about 28 minutes to start from scratch and get an HTTPS Docker cluster with your full application(s) ready.

These are the project generators:

⁠flask-frontend-docker

Project link: https://github.com/tiangolo/flask-frontend-docker⁠

Minimal project generator with a Flask backend, a modern frontend (Vue, React or Angular) using Docker multi-stage building and Nginx, a Traefik load balancer with HTTPS, Docker Compose (and Docker Swarm mode) etc.

⁠full-stack

Project Link: https://github.com/tiangolo/full-stack⁠

Full stack project generator with Flask backend, PostgreSQL DB, PGAdmin, SQLAlchemy, Alembic migrations, Celery asynchronous jobs, API testing, CI integration, Docker Compose (and Docker Swarm mode), Swagger, automatic HTTPS, Vue.js, etc.

⁠full-stack-flask-couchbase

Project Link: https://github.com/tiangolo/full-stack-flask-couchbase⁠

✨ This project generator is the most feature-complete. ✨

Full stack project generator with Flask backend, Couchbase, Couchbase Sync Gateway, Celery asynchronous jobs, API testing, CI integration, Docker Compose (and Docker Swarm mode), Swagger, automatic HTTPS, Vue.js, etc.

Similar to the one above (full-stack), but with Couchbase instead of PostgreSQL, and some more features.

⁠full-stack-flask-couchdb

Project Link: https://github.com/tiangolo/full-stack-flask-couchdb⁠

Full stack project generator with Flask backend, CouchDB, Celery asynchronous jobs, API testing, CI integration, Docker Compose (and Docker Swarm mode), Swagger, automatic HTTPS, Vue.js, etc.

Similar to full-stack-flask-couchbase, but with CouchDB instead of Couchbase (or PostgreSQL).

⁠Quick Start for SPAs *

⁠Modern Single Page Applications

If you are building modern frontend applications (e.g. Vue⁠, React⁠, Angular⁠) you would most probably be compiling a modern version of JavaScript (ES2015, TypeScript, etc) to a less modern, more compatible version.

If you want to serve your (compiled) frontend code by the same backend (Flask) Docker container, you would have to copy the code to the container after compiling it.

That means that you would need to have all the frontend tools installed on the building machine (it might be your computer, a remote server, etc).

That also means that you would have to, somehow, always remember to compile the frontend code right before building the Docker image.

And it might also mean that you could then have to add your compiled frontend code to your git repository (hopefully you are using Git already, or learning how to use git⁠).

Adding your compiled code to Git is a very bad idea for several reasons, some of those are:

  • You don't have a single, ultimate source of truth (the source code).
  • The compiled code might be stale, even when your source code is new, which might make you spend a lot of time debugging.
  • You might run into a lot of code conflicts when interacting with multiple team members with different Git branches, and spend a lot of time solving irrelevant code conflicts in the compiled code.
    • This might also ruin automatic branch merging in pull requests from other team members.

For these reasons, it is not recommended that you serve your frontend code from the same backend (Flask) Docker container.

⁠Better alternative

There's a much better alternative to serving your frontend code from the same backend (Flask) Docker container.

You can have another Docker container with all the frontend tools installed (Node.js, etc) that:

  • Takes your source frontend code.
  • Compiles it and generates the final "distributable" frontend.
  • Uses Docker "multi-stage builds" to copy that compiled code into a pure Nginx Docker image.
  • The final frontend image only contains the compiled frontend code, directly from the source, but has the small size of an Nginx image, with all the performance from Nginx.

To learn the specifics of this process for the frontend building in Docker you can read:

After having one backend (Flask) container and one frontend container, you need to serve both of them.

And you might want to serve them under the same domain, under a different path. For example, the backend (Flask) app at the path /api and the frontend at the "root" path /.

You can then use Traefik⁠ to handle that.

And it can also automatically generate HTTPS certificates for your application using Let's Encrypt. All for free, in a very easy setup.

If you want to use this alternative, check the project generators above⁠, they all use this idea.

In this scenario, you would have 3 Docker containers:

  • Backend (Flask)
  • Frontend (Vue.js, Angular, React or any other)
  • Traefik (load balancer, HTTPS)
⁠Deprecated Single Page Applications guide

If you want to check the previous (deprecated) documentation on adding a frontend to the same container, you can read the deprecated guide for single page apps⁠.

⁠Quick Start for bigger projects structured as a Python package

Note: You can download the example-flask-package-python3.7.zip project example and use it as an example or template for your project from the section Examples above.

You should be able to follow the same instructions as in the "QuickStart" section above, with some minor modifications:

  • Instead of putting your code in the app/ directory, put it in a directory app/app/.
  • Add an empty file __init__.py inside of that app/app/ directory.
  • Add a file uwsgi.ini inside your app/ directory (that is copied to /app/uwsgi.ini inside the container).
  • In your uwsgi.ini file, add:
[uwsgi]
module = app.main
callable = app

The explanation of the uwsgi.ini is as follows:

  • The module in where my Python web app lives is app.main. So, in the package app (/app/app), get the main module (main.py).
  • The Flask web application is the app object (app = Flask(__name__)).

Your file structure would look like:

.
├── app
│   ├── app
│   │   ├── __init__.py
│   │   ├── main.py
│   └── uwsgi.ini
└── Dockerfile

...instead of:

.
├── app
│   ├── main.py
└── Dockerfile

...after that, everything should work as expected. All the other instructions would apply normally.

⁠Working with submodules
  • After adding all your modules you could end up with a file structure similar to (taken from the example project):
.
├── app
│   ├── app
│   │   ├── api
│   │   │   ├── api.py
│   │   │   ├── endpoints
│   │   │   │   ├── __init__.py
│   │   │   │   └── user.py
│   │   │   ├── __init__.py
│   │   │   └── utils.py
│   │   ├── core
│   │   │   ├── app_setup.py
│   │   │   ├── database.py
│   │   │   └── __init__.py
│   │   ├── __init__.py
│   │   ├── main.py
│   │   └── models
│   │       ├── __init__.py
│   │       └── user.py
│   └── uwsgi.ini
└── Dockerfile

from .core import app_setup

or

from app.core import app_setup
  • And if you are in app/app/api/endpoints/user.py and you want to import the users object from app/app/core/database.py you would write it like:
from ...core.database import users

or

from app.core.database import users

⁠Advanced instructions

You can customize several things using environment variables.

⁠Serve index.html directly

Notice: this technique is deprecated, as it can create several issues with modern frontend frameworks. For the details and better alternatives, read the section above.

Setting the environment variable STATIC_INDEX to be 1 you can configure Nginx to serve the file in the URL /static/index.html when requested for /.

That would improve speed as it would not involve uWSGI nor Python. Nginx would serve the file directly. To learn more follow the section above "QuickStart for SPAs".

For example, to enable it, you could add this to your Dockerfile:

ENV STATIC_INDEX 1
⁠Custom uWSGI process number

By default, the image starts with 2 uWSGI processes running. When the server is experiencing a high load, it creates up to 16 uWSGI processes to handle it on demand.

If you need to configure these numbers you can use environment variables.

The starting number of uWSGI processes is controlled by the variable UWSGI_CHEAPER, by default set to 2.

The maximum number of uWSGI processes is controlled by the variable UWSGI_PROCESSES, by default set to 16.

Have in mind that UWSGI_CHEAPER must be lower than UWSGI_PROCESSES.

So, if, for example, you need to start with 4 processes and grow to a maximum of 64, your Dockerfile could look like:

FROM tiangolo/uwsgi-nginx-flask:python3.7

ENV UWSGI_CHEAPER 4
ENV UWSGI_PROCESSES 64

COPY ./app /app
⁠Max upload file size

You can set a custom maximum upload file size using an environment variable NGINX_MAX_UPLOAD, by default it has a value of 0, that allows unlimited upload file sizes. This differs from Nginx's default value of 1 MB. It's configured this way because that's the simplest experience an inexperienced developer in Nginx would expect.

For example, to have a maximum upload file size of 1 MB (Nginx's default) add a line in your Dockerfile with:

ENV NGINX_MAX_UPLOAD 1m
⁠Custom listen port

By default, the container made from this image will listen on port 80.

To change this behavior, set the LISTEN_PORT environment variable. You might also need to create the respective EXPOSE Docker instruction.

You can do that in your Dockerfile, it would look something like:

FROM tiangolo/uwsgi-nginx-flask:python3.7

ENV LISTEN_PORT 8080

EXPOSE 8080

COPY ./app /app
⁠Custom uwsgi.ini configurations

There is a default file in /app/uwsgi.ini with app specific configurations (on top of the global uwsgi configurations).

It only contains:

[uwsgi]
module = main
callable = app
  • module = main refers to the file main.py.
  • callable = app refers to the Flask "application", in the variable app.

You can customize uwsgi by replacing that file with your own, including all your configurations.

For example, to extend the default one above and enable threads, you could have a file:

[uwsgi]
module = main
callable = app
enable-threads = true
⁠Custom uwsgi.ini file location

You can override where the image should look for the app uwsgi.ini file using the envirnoment variable UWSGI_INI.

With that you could change the default directory for your app from /app to something else, like /application.

For example, to make the image use the file in /application/uwsgi.ini, you could add this to your Dockerfile:

ENV UWSGI_INI /application/uwsgi.ini

COPY ./application /application
WORKDIR /application

Note: the WORKDIR is important, otherwhise uWSGI will try to run the app in /app.

Note: you would also have to configure the static files path, read below.

⁠Custom ./static/ path

You can make Nginx use a custom directory path with the files to serve directly (without having uWSGI involved) with the environment variable STATIC_PATH.

For example, to make Nginx serve the static content using the files in /app/custom_static/ you could add this to your Dockerfile:

ENV STATIC_PATH /app/custom_static

Then, when the browser asked for a file in, for example, http://example.com/static/index.html⁠, Nginx would answer directly using a file in the path /app/custom_static/index.html.

Note: you would also have to configure Flask to use that as its static directory.

As another example, if you needed to put your application code in a different directory, you could configure Nginx to serve those static files from that different directory.

If you needed to have your static files in /application/static/ you could add this to your Dockerfile:

ENV STATIC_PATH /application/static
⁠Custom /static URL

You can also make Nginx serve the static files in a different URL, for that, you can use the environment variable STATIC_URL.

For example, if you wanted to change the URL /static to /content you could add this to your Dockerfile:

ENV STATIC_URL /content

Then, when the browser asked for a file in, for example, http://example.com/content/index.html⁠, Nginx would answer directly using a file in the path /app/static/index.html.

⁠Custom /app/prestart.sh

If you need to run anything before starting the app, you can add a file prestart.sh to the directory /app. The image will automatically detect and run it before starting everything.

For example, if you want to add Alembic SQL migrations (with SQLALchemy), you could create a ./app/prestart.sh file in your code directory (that will be copied by your Dockerfile) with:

#! /usr/bin/env bash

# Let the DB start
sleep 10;
# Run migrations
alembic upgrade head

and it would wait 10 seconds to give the database some time to start and then run that alembic command.

If you need to run a Python script before starting the app, you could make the /app/prestart.sh file run your Python script, with something like:

#! /usr/bin/env bash

# Run custom Python script before starting
python /app/my_custom_prestart_script.py

Note: The image uses source to run the script, so for example, environment variables would persist. If you don't understand the previous sentence, you probably don't need it.

⁠Custom Nginx processes number

By default, Nginx will start one "worker process".

If you want to set a different number of Nginx worker processes you can use the environment variable NGINX_WORKER_PROCESSES.

You can use a specific single number, e.g.:

ENV NGINX_WORKER_PROCESSES 2

or you can set it to the keyword auto and it will try to autodetect the number of CPUs available and use that for the number of workers.

For example, using auto, your Dockerfile could look like:

FROM tiangolo/uwsgi-nginx-flask:python3.7

ENV NGINX_WORKER_PROCESSES auto

COPY ./app /app
⁠Custom Nginx maximum connections per worke

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over 7 years ago

docker pull lnls/uwsgi-nginx-flask:python3.6