This is a forked repo from https://github.com/tiangolo/uwsgi-nginx-flask-docker. A very well maintained repo. Much respect. I suggest you may prefer his repo over this one. I chose to fork it so that I could remove some of the options and "harden" the container somewhat. A specific purpose was chosen to focus on micro-service applications using this configuration.
Docker image with uWSGI and Nginx for Flask web applications in Python 3.6 running in a single container using Alpine Linux. All libraries and packages are specific versions known to work together.
This Docker image allows you to create Flask web applications in Python that run with uWSGI and Nginx in a single container.
uWSGI with Nginx is one of the best ways to deploy a Python web application, so you should have good performance (check the benchmarks) with this image.
GitHub repo: https://github.com/chuckamus-prime/uwsgi-nginx-flask-docker
Docker Hub image:
python3.6-alpine3.7tag: general Flask web application:
example-flask-python3.6-alpine3.7.zip
python3.6-alpine3.7tag: 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-python3.6-alpine3.7.zip
Clone this repo, and then run the following command in the base directory:
./buildBaseImage.sh
Since thie image is not in dockerhub (yet), the script above will put the base container image in your local repo.
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 python docker container using alpine linux. This Docker image adds uWSGI with Flask and Nginx, installed in the same container. This will serve as a base for micro-services written in python.
Note: You can download the example-flask-python3.6.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
Dockerfilewith:
FROM chuckamus-prime/uwsgi-nginx-flask:python3.6-alpine3.7
COPY ./app /app- Create an
appdirectory and enter in it - Create a
main.pyfile (it should be named like that and should be in yourappdirectory) 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=9000)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
Dockerfileis, containing yourappdirectory) - Build your Flask image:
docker build -t myimage .- Run a container based on your image:
docker run -d --name mycontainer -p 443:443 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: https://192.168.99.100:443/
Note: You can download the example-flask-package-python3.6.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 directoryapp/app/. - Add an empty file
__init__.pyinside of thatapp/app/directory. - Add a file
uwsgi.iniinside yourapp/directory (that is copied to/app/uwsgi.iniinside the container). - In your
uwsgi.inifile, add:
[uwsgi]
module = app.main
callable = appThe explanation of the uwsgi.ini is as follows:
- The module in where my Python web app lives is
app.main. So, in the packageapp(/app/app), get themainmodule (main.py). - The Flask web application is the
appobject (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.
- 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
-
Make sure you follow the offical docs while importing your modules:
-
For example, if you are in
app/app/main.pyand want to import the module inapp/app/core/app_setup.pyyou would wirte it like:
from .core import app_setupor
from app.core import app_setup- And if you are in
app/app/api/endpoints/user.pyand you want to import theusersobject fromapp/app/core/database.pyyou would write it like:
from ...core.database import usersor
from app.core.database import usersYou can customize several things using environment variables.
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 a developer that is not expert 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 1mYou 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 /applicationNote: 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.
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 headand 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.yNote: 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.
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 2or 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 chuckamus-prime/uwsgi-nginx-flask:python3.6-alpine3.7
ENV NGINX_WORKER_PROCESSES auto
COPY ./app /appBy default, Nginx will start with a maximum limit of 1024 connections per worker.
If you want to set a different number you can use the environment variable NGINX_WORKER_CONNECTIONS, e.g:
ENV NGINX_WORKER_CONNECTIONS 2048It cannot exceed the current limit on the maximum number of open files. See how to configure it in the next section.
The number connections per Nginx worker cannot exceed the limit on the maximum number of open files.
You can change the limit of open files with the environment variable NGINX_WORKER_OPEN_FILES, e.g.:
ENV NGINX_WORKER_OPEN_FILES 2048If you need to configure Nginx further, you can add *.conf files to /etc/nginx/conf.d/ in your Dockerfile.
Just have in mind that the default configurations are created during startup in a file in /etc/nginx/conf.d/nginx.conf and /etc/nginx/conf.d/upload.conf. So you shouldn't overwrite them. You should name your *.conf file with something different than nginx.conf or upload.conf.
One of the best ways to deploy a Python web application is with uWSGI and Nginx, as seen in the benchmarks.
Roughly:
-
Nginx is a web server, it takes care of the HTTP connections and also can serve static files directly and more efficiently.
-
uWSGI is an application server, that's what runs your Python code and it talks with Nginx.
-
Your Python code has the actual Flask web application, and is run by uWSGI.
The image uses the official Python Docker image, installs Nginx, uWSGI and flask.
And it controls all these processes with Supervisord.
If you follow the instructions and keep the root directory /app in your container, with a file named main.py and a Flask object named app in it, it should "just work".
There's already a uwsgi.ini file in the /app directory with the uWSGI configurations for it to "just work". And all the other required parameters are in another uwsgi.ini file in the image, inside /etc/uwsgi/.
If you need to change the main file name or the main Flask object, you would have to provide your own uwsgi.ini file. You may use the one in this repo as a template to start with (and you only would have to change the 2 corresponding lines).
You can have a /app/static directory and those files will be efficiently served by Nginx directly (without going through your Flask code or even uWSGI), it's already configured for you. But you can configure it further using environment variables (read above).
Supervisord takes care of running uWSGI with the uwsgi.ini file in /app file (including also the file in /etc/uwsgi/uwsgi.ini) and starting Nginx.
There's the rule of thumb that you should have "one process per container".
That helps, for example, isolating an app and its database in different containers.
But if you want to have a "micro-services" approach you may want to have more than one process in one container if they are all related to the same "service", and you may want to include your Flask code, uWSGI and Nginx in the same container (and maybe run another container with your database).
That's the approach taken in this image.
This image (and tags) have some default files, so if you run it by itself (not as the base image of your own project) you will see a default "Hello World" web app.
When you build a Dockerfile with a COPY ./app /app you replace those default files with your app code.
The main default file is only in /app/main.py. And in the case of the tags with -index, also in /app/static/index.html.
But those files render a "(default)" text in the served web page, so that you can check if you are seeing the default code or your own code overriding the default.
Your app code should be in the container's /app directory, it should have a main.py file and that main.py file should have a Flask object app.
If you follow the instructions above or use one of the downloadable example templates, you should be OK.
There is also a /app/uwsgi.ini file inside the images with the default parameters for uWSGI.
The downloadable examples include a copy of the same uwsgi.ini file for debugging purposes. To learn more, read the "Advanced development instructions" below.
While developing, you might want to make your code directory a volume in your Docker container.
With that you would have your files (temporarily) updated every time you modify them, without needing to build your container again.
To do this, you can use the command pwd (print working directory) inside your docker run and the flag -v for volumes.
With that you could map your ./app directory to your container's /app directory.
But first, as you will be completely replacing the directory /app in your container (and all of its contents) you will need to have a uwsgi.ini file in your ./app directory with:
[uwsgi]
module = main
callable = appand then you can do the Docker volume mapping.
Note: A uwsgi.ini file is included in the downloadable examples.
- To try it, go to your project directory (the one with your
Dockerfileand your./appdirectory) - Make sure you have a
uwsgi.inifile in your./appdirectory - Build your Docker image:
docker build -t myimage .- Run a container based on your image, mapping your code directory (
./app) to your container's/appdirectory: bash
docker run -d --name mycontainer -p 443:443 -v $(pwd)/app:/app myimage
If you go to your Docker container URL you should see your app, and you should be able to modify files in ./app/static/ and see those changes reflected in your browser just by reloading.
...but, as uWSGI loads your whole Python Flask web application once it starts, you won't be able to edit your Python Flask code and see the changes reflected.
To be able to (temporarily) debug your Python Flask code live, you can run your container overriding the default command (that starts Supervisord which in turn starts uWSGI and Nginx) and run your application directly with python, in debug mode, using the flask command with its environment variables.
So, with all the modifications above and making your app run directly with flask, the final Docker command would be:
docker run -d --name mycontainer -p 443:443 -v $(pwd)/app:/app -e FLASK_APP=main.py -e FLASK_DEBUG=1 myimage flask run --host=0.0.0.0 --port=9000Or in the case of a package project, you would set FLASK_APP=main/main.py:
docker run -d --name mycontainer -p 443:443 -v $(pwd)/app:/app -e FLASK_APP=main/main.py -e FLASK_DEBUG=1 myimage flask run --host=0.0.0.0 --port=9000Now you can edit your Flask code in your local machine and once you refresh your browser, you will see the changes live.
Remember that you should use this only for debugging and development, for deployment in production you shouldn't mount volumes and you should let Supervisord start and let it start uWSGI and Nginx (which is what happens by default).
An alternative for these last steps to work when you don't have a package but just a flat structure with single files (modules), your Python Flask code could have that section with:
if __name__ == "__main__":
# Only for debugging while developing
app.run(host='0.0.0.0', debug=True, port=9000)...and you could run it with python main.py. But that will only work when you are not using a package structure and don't plan to do it later. In that specific case, if you didn't add the code block above, your app would only listen to localhost (inside the container), in another port (5000) and not in debug mode.
Note: The example project example-flask-python3.6 includes a docker-compose.yml and docker-compose.debug-override.yml with all these configurations, if you are using Docker Compose.
If you follow the instructions above, it's probable that at some point, you will write code that will break your Flask debugging server and it will crash.
And since the only process running was your debugging server, that now is stopped, your container will stop.
Then you will have to start your container again after fixing your code and you won't see very easily what is the error that is crashing your server.
So, while developing, you could do the following (that's what I normally do, although I do it with Docker Compose, as in the example projects):
- Make your container run and keep it alive in an infinite loop (without running any server):
docker run -d --name mycontainer -p 443:443 -v $(pwd)/app:/app -e FLASK_APP=main.py -e FLASK_DEBUG=1 myimage bash -c "while true ; do sleep 10 ; done"- Or, if your project is a package, set
FLASK_APP=main/main.py:
docker run -d --name mycontainer -p 443:443 -v $(pwd)/app:/app -e FLASK_APP=main/main.py -e FLASK_DEBUG=1 myimage bash -c "while true ; do sleep 10 ; done"- Connect to your container with a new interactive session:
docker exec -it mycontainer bashYou will now be inside your container in the /app directory.
- Now, from inside the container, run your Flask debugging server:
flask run --host=0.0.0.0 --port=9001You will see your Flask debugging server start, you will see how it sends responses to every request, you will see the errors thrown when you break your code and how they stop your server and you will be able to re-start your server very fast, by just running the command above again.
2018-07-10:
- created paths for certificates to be injected into containers
- changed the default port from 80 to 9000 for the flask app to run under when not ran within uwsgi and nginx. (docker-compose.debug-override.yml is used)
- Changed the docker-compose override file name so it wouldn't automatically be used.
- Removed references to static content serving.
- Changed ports in documentation and nginx configuration from 80 to 443
- Removed deprecated code/examples
- Consolidated to the python 3.6 version using Alpine Linux
- Specified the version of Flask for pip
- merged Sebastián Ramírez's base container and its necessary files https://github.com/tiangolo/uwsgi-nginx-docker into one base image with more control in one base image and prescribing flask
2018-06-27:
- Forked from https://github.com/tiangolo/uwsgi-nginx-flask-docker.
- (refer to that repo for prior hisory)
This project is licensed under the terms of the Apache license.