nginx + uwsgi + flask - disabling custom error pages

Question

Is it possible to disable nginx\'s custom error pages - if I may call them that - to display my framework\'s exception pages?

I can\'t really see my werkzeug debugge

Answer 1

Use Flask#errorhandler to register your own error handlers in flask. For example to replace the 404 you would do something like:

app = Flask()

@app.errorhandler(404)
def handel_404(error):
    return render_template('404.html')

Answer 2

This "Internal Server Error" page is not from nginx but from Flask. It does so when debug mode is off.

uwsgi is importing your code as a module, not running at as a script. __name__ == '__main__' is False and the if statement is not executed. Try setting debug mode outside of the if:

app = Flask(__name__)
app.debug = True

However, it is strongly recommended to never leave the debug mode on a server on the public internet, since the user can make the server run any code. This is a serious security issue.

Answer 3

Simon Sapin has really given you the correct answer. You need to enable debug in Flask. Nginx does not return any custom error pages unless you explictly configure it to do so.

If you use the following code you will see your debug messages from flask, proxied via Nginx.

from flask import Flask

app = Flask(__name__)
app.debug = True

@app.route('/')
def index():
    raise Exception()

As per your update 2. You are seeing a 502 (bad gateway) because Flask is simply not returning any response at all, or a response that Nginx does not understand. A 502 is not a problem with Nginx. It means that whatever Nginx is trying to talk (your flask app in this case) is not working properly at all.

However, in many ways you shouldn't be doing this. Debugging mode should only be enabled when you are running flask on your local dev machine. Which is the whole point of the if __name__ == "__main__": line anyway.