fastwsgi blocks OTHER threads from executing

[ibrewster]

Calling fastwsgi.run should block the main thread, but release the GIL, allowing other threads to run (I/O wait). However, the observed behavior is that all threads are blocked, implying the GIL is not released while fastwsgi is waiting (though the actual issue may be different).

Observe the difference in behavior with this toy code when using fastwsgi.run vs. the development flask app.run

import threading, time
import fastwsgi

from flask import Flask

app = Flask(__name__)

@app.get('/')
def hello_world():
    return 'Hello, World!', 200


def dummy_thread():
    while True:
        print("Staying alive!")
        time.sleep(1)
 
if __name__ == '__main__':
    thread = threading.Thread(target=dummy_thread)
    thread.start()
    time.sleep(3) # Should print "Staying alive!" a number of times
    
    # This should block the main thread, but the "staying alive" thread should keep running
    # Using fastwsgi, all stops.
    fastwsgi.run(wsgi_app=app, host='0.0.0.0', port=5000)
    
    # Using the flask provided development server, the other thread continues as expected.
    # app.run(host='0.0.0.0', port=5000)

In many (most?) apps this would not be an issue, however it makes fastwsgi unusable in any application that requires some sort of background processing, such as my RaspberryPi app that provides a web server, but also listens for button presses.

[remittor]

import threading, time
import fastwsgi

from flask import Flask

app = Flask(__name__)

@app.get('/')
def hello_world():
    return 'Hello, World!', 200

def dummy_thread():
    while True:
        print("Staying alive!")
        time.sleep(1)

if __name__ == '__main__':
    thread = threading.Thread(target = dummy_thread)
    thread.start()
    time.sleep(3) # Should print "Staying alive!" a number of times

    srv = fastwsgi.server
    srv.host = '0.0.0.0'
    srv.port = 5000
    srv.loglevel = 6
    #srv.allow_keepalive = 0
    srv.hook_sigint = 1   # intercepting the SIGINT signal inside the REST API request handler
    srv.nowait = 2        # enabling periodic maintenance of REST API requests
    rc = srv.init(app)
    if rc != 0:
        print(f"ERROR: cannot init REST API server (err = {rc})")
        exit(rc)
    
    print(f"REST API server listening at http://{srv.host}:{srv.port}")
    
    while True:
        # processing REST API requests
        rc = srv.run()
        if rc != 0:
            print(f"REST API return code = {rc}")
            break
        # asynchronous task execution (without waiting for a REST API request)
        # do something in background
        time.sleep(0)
    
    srv.close()
    print("===== FastWSGI server finish =====")

[Louciole]

Hi guys !
I have the same issue as ibrewster, i would like to be able to run some websockets in the background, I understand that i can unblock my GIL with the proposed solution, but I have some issue with it :

• srv.nowait = 2 does not have any sense since the value is just used once as a boolean in fastwsgi.py
• It still does not loop by itself.

Is there a cleaner solution ?

[remittor]

@Louciole , look this func:

fastwsgi/fastwsgi/server.c

Line 924 in 5572bb3

PyObject * run_nowait(PyObject * self, PyObject * server)