Serve Flask App With XAMPP Apache on Windows
As we all know Flask, Flask is a web microframework written in python. Flask has a lot of advantages including (for myself) is an easy and agile way of developing web services. Unfortunately, not really agile in a way of deploying into production. That’s why I decided to make this article to tell people how difficult and hideous it is to deploy a Flask app to XAMPP Apache web service and another reason is to make sure I won’t get trouble if I had to deploy Flask again.
So, to deploy our Flask app, our main module to use is called mod-wsgi. This library is maintained by someone called Graham Dumpleton (even though I wrote this article without asking his approval), and I’d like to say thank you so much for maintaining this wonderful tools for us.
Now let’s jump into technical things. Before I know anything about mod-wsgi, I found a tutorial by Thilina Madumal on how exactly to serve a Flask app on Apache. And before you read this article any further, I suggest you read that article first in here.
Prerequisites
As mentions by Madumal in his article above, you’re going to need to prepare some installations.
- Visual C++ Redistributable for Visual Studio
- Visual C++ Build Tools (https://visualstudio.microsoft.com/visual-cpp-build-tools/)
- python3 (Installed for all user, so make sure installation directory doesn’t go to “C:/Users”)
- python3-pip
- XAMPP Apache
And this is going to be very important in windows machine
MAKE SURE YOU INSTALLED PYTHON, APACHE, AND VISUAL STUDIO AS THE SAME BINARY. For example, all of them are 32-bit version OR all of them are 64-bit version.
Because if you didn’t make all of that with the same binary, you’re going to face a lot of errors. This statement also mentioned by Graham in this link. As for me myself, I used the 64-bit version of Python 3.8, and 64-bit version of XAMPP Apache (yes, there is a 64-bit version of it).
After you installed all of that to your machine, I’m going to assume you have installed python and apache in an easy directory.
For Python directory, I’m assuming it will be residing in the program files directory, so it’s going to be something like “C:/Program Files/Python”. Because that’s the default path for all user installation. We are going to call that <Python Home> directory for this article.
And for XAMPP Apache, it would be something like “C:/XAMPP/Apache” and we’ll call that <Apache Home> directory.
Run Apache as a Windows Service
Now, I can’t tell you right now on why would you need to install it as a windows service. Because I personally don’t understand it either. But from my personal experience, using apache as a windows service can help me understanding an occurring error. To do that, open up your command prompt as administrators.
Change your directory to <Apache Home>/bin
cd C:/XAMPP/Apache/bin
After that type a command
httpd.exe -k install
This is what I mean by understanding errors in apache. Because as you might not know, the whole process of serving Flask in apache won’t show most errors in the error logs. And because of that, I was having a hard time understanding what’s going on with my apache. Using it as windows services I can control most of what’s going on with my apache.
Now after you installed it as windows services, you can use another command including start, stop, restart the server, or even uninstalling apache from windows service. Use the command like
httpd.exe -k [command]
After you start the server, test it by opening your localhost and it should show xampp welcome page.
Installing mod_wsgi
Now, the first wave of errors is going to show up from this step onward. Whatever errors you might get you need to stay calm and cold-minded. I’ll try to address most of the errors I encountered myself, as well as steps on how to deal with it.
Before you install mod-wsgi directly, I assume most of you are using the virtual environment to develop a Flask app. But if you didn’t, it’s not a big deal. I will suggest you to make your virtual environment inside your working project, that way it will be easier to install a requirement for your project (although many people oppose this method). So, if you worked with a virtual environment, prepare it before you install mod-wsgi.
Thilina Madumal in his tutorial suggests activating your virtual environment before installing mod-wsgi. But, I’m going to suggest you to not use or activate your virtual environment. Because I had trouble loading mod-wsgi to Apache if I used a virtual environment, so I installed mod-wsgi directly to my main Python directory. Don’t worry, you’ll still be able to use a virtual environment for your project.
Now we are going to pip install mod-wsgi to Python. Before you type pip install command in the command prompt, I suggest you set an environment variable first. It’s as easy as
set MOD_WSGI_APACHE_ROOTDIR=<Apache Home>
This is just to ensure no errors that say “no apache directory set”. After that we can finally pip install mod-wsgi
pip install mod-wsgi
Now, if you encounter any errors doing this step, I suggest you try installing a different version of mod-wsgi in this link. I encountered 3 types of errors while installing mod-wsgi. First, no apache directory set, second is an unresolved external symbol, and third is filename.whl is not supported wheel on this platform.
The first error we can avoid by setting the apache root directory. The second and third errors, however, are a bit tricky. Basically, you need the right version of mod-wsgi for your python, so try to install it using a different version from the link I mentioned before.
Using mod-wsgi in Apache Server
After you successfully installed mod-wsgi to your Python, run this command in command prompt
mod_wsgi-express module-config
It will print a configuration for us to put into the apache. It should print out something like
LoadFile “C:/Python38/python38.dll”
LoadModule wsgi_module “C:/python38/lib/site-packages/mod_wsgi/server/mod_wsgi.cp38-win_amd64.pyd”
WSGIPythonHome “C:/Python38”
Copy the output of that command. Now open up apache configuration file in <Apache Home>/conf/httpd.conf and paste the output before any LoadModule statement.
Note: For further details please refer to https://github.com/GrahamDumpleton/mod_wsgi#connecting-into-apache-installation
You might want to restart and test your apache server at this point because I also encountered an error in this step. But I dealt with that error by simply installing mod-wsgi in my main python directory (without virtual environment). If somehow you insist to install it in your virtual environment, the LoadModule and PythonHome path will be different from the example above (it will point to your virtual environment directory). But, as long as no errors shown up and your server is starting without problem, then it’s okay to use a virtual environment.
Another error I encountered is “Cannot load module into server: %1 is not a valid Win32 application”. These errors mean there’s a different binary version of application you’re using. Either it’s Python, Apache, or even mod-wsgi itself.
After dealing with that errors and get your server running again, you might want to add a listen port. This is so you won’t be using the default port Apache is using, which is port 80. Just add a line “Listen <port>” in your httpd.conf
Using VirtualHost for Flask App
After we configure the main config, open up the virtual host config in apache. It’s located at <Apache Home>/conf/extra/httpd-vhosts.conf. Now copy this line in your vhost configuration
<VirtualHost *:5000>
ServerAdmin admin-name-here
ServerName server-name-here (e.g:localhost:5000)
WSGIScriptAlias / “F:/myapp/app/index/web.wsgi”
DocumentRoot “F:/myapp”
<Directory “F:/myapp/app/index”>
Require all granted
Options Indexes FollowSymLinks Includes ExecCGI
</Directory>
AddHandler wsgi-script .wsgi
ErrorLog “F:/myapp/logs/error.log”
CustomLog “F:/myapp/logs/access.log” common
</VirtualHost>
If you haven’t created an error log or access log, you may need to create it manually. These logs will prove to be useful from here onward.
You might notice that my configuration is a little bit different from Thilina Madumal’s configuration here. That is because his configuration apparently isn't enough for my case. And as he mentions there, there are three important things in that configuration.
- Server Name (Domain for your app if you have it, or simply localhost)
- WSGIScriptAlias (Tells apache what script to execute when there’s a request for that domain)
- <Directory> (For security purpose, it should allow access to wsgi script but not the entire project)
So what did I add to the configuration? Apparently, if I run a configuration like Thilina Madumal’s, I get an error “AH02809: Options ExecCGI is off in this directory: F:/myapp/app/index/web.wsgi”. So I add a line inside Directory tag
Options Indexes FollowSymLinks Includes ExecCGI
It may just need the ‘Includes ExecCGI’ part, but I copied the entire line from Apache’s main config (httpd.conf). After that, I still got an error. This time it says “F:/myapp/app/index/web.wsgi is not executable; ensure interpreted scripts have “#!” or “‘!” first line”. That error statement suggests you to add what we called Shebang or interpreter. But I didn't need that. I just need to add a line
AddHandler wsgi-script .wsgi
This is to ensure that wsgi script would be handled by apache handler.
And that’s what I changed in virtual host configuration. You might not get these errors yet because you haven’t created the wsgi file just yet. But before you create it, go back to httpd.conf and search for “httpd-vhosts.conf” Make sure there is a line that says
# Virtual hosts
Include conf/extra/httpd-vhosts.conf
Create a WSGI Script
You need to keep in mind that you might want to change some directory order of your project. This is to ensure no circular import in your python app and enforce security in your web app. Feel free to do some trial and error for your project directory, if you changed your directory order you need to make sure the directory is still correct in vhosts configuration.
First, create the wsgi script manually (my script is called web.wsgi) and then change the content (using notepad or vscode or any other text editor). Then add this python command to your script
activate_this = ‘F:/myapp/env/Scripts/activate_this.py’
with open(activate_this) as file_:
exec(file_.read(), dict(__file__=activate_this))
import sys
sys.path.insert(0, ‘F:/myapp’)
from your-app-script import app as application
The ‘activate this part’ is only used if you’re working with a virtual environment. If you didn’t use any virtual environment you just need the import sys and below for your script. For more reference read this link: https://flask.palletsprojects.com/en/1.1.x/deploying/mod_wsgi/
your-app-script should be something like
from flask import Flask
app = Flask(__name__)
@app.route(“/”)
def hello():
return “Hello World”
if __name__ == “__main__”:
app.run()
And that would be the last configuration you need to serve your Flask app to XAMPP Apache server on windows.
And again, you might encounter some errors when starting your apache server. Try as hard as you can to figure out the errors. You can check the Apache error log, your app error log, or from command prompt when you start your server.
From my personal experience, most of the errors doesn’t have proper documentation on how to handle them. So most of the time my way to handle those errors is from a completely different context. I will link some major documentation about this issue and I hope no one would encounter as much trouble as I did (I spent a whole two weeks just to work for those errors).
Thank you so much for reading this article. And special thanks for Graham Dumpleton for maintaining mod-wsgi and keep active answering questions in many platforms including GitHub, StackOverflow, or even some google groups. And Thilina Madumal for making me understand a base step to configure all of this.
