Menu
Just starting to play around with Flask on a local server and I'm noticing the request/response times are way slower than I feel they should be.
Just a simple server like the following takes close to 5 seconds to respond.
from flask import Flask app = Flask(__name__) @app.route("/") def index(): return "index" if __name__ == "__main__": app.run() Any ideas? Or is this just how the local server is?
201
When Flask app runs slow we need to identify what is the bottleneck. It can be an overloaded database, unresponsive external API, or heavy, CPU-intensive computation.
Flask will process one request per thread at the same time. If you have 2 processes with 4 threads each, that's 8 concurrent requests.
The server component that comes with Flask is really only meant for when you are developing your application; even though it can be configured to handle concurrent requests with app. run(threaded=True) (as of Flask 1.0 this is the default).
Ok I figured it out. It appears to be an issue with Werkzeug and os's that support ipv6.
From the Werkzeug site http://werkzeug.pocoo.org/docs/serving/:
On operating systems that support ipv6 and have it configured such as modern Linux systems, OS X 10.4 or higher as well as Windows Vista some browsers can be painfully slow if accessing your local server. The reason for this is that sometimes “localhost” is configured to be available on both ipv4 and ipv6 socktes and some browsers will try to access ipv6 first and then ivp4.
So the fix is to disable ipv6 from the localhost by commenting out the following line from my hosts file:
::1 localhost Once I do this the latency problems go away.
I'm really digging Flask and I'm glad that it's not a problem with the framework. I knew it couldn't be.
133
Add "threaded=True" as an argument to app.run(), as suggested here: http://arusahni.net/blog/2013/10/flask-multithreading.html
For example: app.run(host="0.0.0.0", port=8080, threaded=True)
The ipv6-disabling solution did not work for me, but this did.
21
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
