CODEWITHSUNDEEP
pythonflaskgevent
ling7334
ling7334

Reputation: 454

Gevent WSGIServer don't respond

Background

I'm attempting to serve a flask REST API which using gevent wsgiserver. It worked in Werkzeug, but did not respond in gevent wsgiserver. Here is a simple flask app serve by gevent wsgiserver.

import gevent
from gevent.pywsgi import WSGIServer
from flask import Flask

app = Flask(__name__)

@app.route('/', methods=['GET'])
def index_get():
    return 'OK'

if __name__ == '__main__':
    # app.run(host='0.0.0.0',port=80, threaded=True, debug=False)
    WSGIServer(('0.0.0.0', 80), app).serve_forever()

Investigation

Python-3.5.2
flask-0.11.1
gevent-1.2.1

The browser keep loading the response. However the server console show it already give the response. Accidentally, I change the code

@app.route('/', methods=['GET'])
def index_get():
    return 'Worked'

And the browser receive the response successfully. I found it fail to respond only when response string is a one or two character string.

Questions

Can anyone confirmed this issue?
What is the mechanism in it?
How can I workaround so I can respond a two character string?

Upvotes: 2

Views: 1236

Answers (1)

ling7334
ling7334

Reputation: 454

OK， I really should read the tutorial first.
According to the tutorial
The stream is closed when a size zero chunk is sent.
I should append a zero size chunk like '\n'

@app.route('/', methods=['GET'])
def index_get():
    return json.dumps({'ReturnCode':200,'message':'command sent.'}) + '\n'

It appear gevent's WSGIServer is a little different from Werkzeug. I should make some change to suit it. The recommended application is different from flask. Although, just append a '\n' also worked for me.

from gevent.wsgi import WSGIServer

def application(environ, start_response):
    status = '200 OK'
    body = '<p>Hello World</p>'

    headers = [
        ('Content-Type', 'text/html')
    ]

    start_response(status, headers)
    return [body]

WSGIServer(('', 8000), application).serve_forever()

Upvotes: 2

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