WebSocket OSError: headers already sent.

[liu,guoshun]

1.uwsgi --http 0.0.0.0:8066 --module toraji.wsgi --master --processes 1 --threads 8 --http-websockets

*** Starting uWSGI 2.0.18 (64bit) on [Wed Aug 19 09:28:05 2020] ***
compiled with version: 4.4.7 20120313 (Red Hat 4.4.7-11) on 15 July 2020 02:09:52
os: Linux-2.6.32-504.23.4.el6.x86_64 #1 SMP Tue Jun 9 20:57:37 UTC 2015
nodename: toraji_dba
machine: x86_64
clock source: unix
pcre jit disabled
detected number of CPU cores: 4
current working directory: /apps/svr/shun/toraji
detected binary path: /usr/local/bin/uwsgi
uWSGI running as root, you can use --uid/--gid/--chroot options
*** WARNING: you are running uWSGI as root !!! (use the --uid flag) ***
your processes number limit is 65536
your memory page size is 4096 bytes
detected max file descriptor number: 1024
lock engine: pthread robust mutexes
thunder lock: disabled (you can enable it with --thunder-lock)
uWSGI http bound on 0.0.0.0:8066 fd 4
uwsgi socket 0 bound to TCP address 127.0.0.1:41844 (port auto-assigned) fd 3
uWSGI running as root, you can use --uid/--gid/--chroot options
*** WARNING: you are running uWSGI as root !!! (use the --uid flag) ***
Python version: 3.6.0 (default, Dec 8 2018, 21:49:17) [GCC 4.4.7 20120313 (Red Hat 4.4.7-11)]
Python main interpreter initialized at 0x15540e0
uWSGI running as root, you can use --uid/--gid/--chroot options
*** WARNING: you are running uWSGI as root !!! (use the --uid flag) ***
python threads support enabled
your server socket listen backlog is limited to 100 connections
your mercy for graceful operations on workers is 60 seconds
mapped 292224 bytes (285 KB) for 8 cores
*** Operational MODE: threaded ***
WSGI app 0 (mountpoint='') ready in 2 seconds on interpreter 0x15540e0 pid: 23945 (default app)
uWSGI running as root, you can use --uid/--gid/--chroot options
*** WARNING: you are running uWSGI as root !!! (use the --uid flag) ***
*** uWSGI is running in multiple interpreter mode ***
spawned uWSGI master process (pid: 23945)
spawned uWSGI worker 1 (pid: 23950, cores: 8)
spawned uWSGI http 1 (pid: 23951)

2.Django as backend
cat views_os.py

import json
import logging
logger = logging.getLogger(__name__)
import uwsgi
from django.http import HttpResponse
def test_socket_api(request):
    uwsgi.websocket_handshake()
    data = uwsgi.websocket_recv()
    data = data.decode()
    data = json.loads(data)
    logger.debug(data)
    os_cmd = "/tmp/mha.sh test socket" #test cmd
    logger.info("##mha socket test cmd:%s",os_cmd)
    uwsgi.websocket_send(os_cmd)
    logger.info("done.")
    return HttpResponse(None)

3. Got errors :

    2020-08-19 09:32:52,029 [uWSGIWorker1Core0:139922668804032] [mysqlha.views_os 14] [DEBUG]- {'a': 1}
    2020-08-19 09:32:52,030 [uWSGIWorker1Core0:139922668804032] [mysqlha.views_os 16] [INFO]- ##mha socket test cmd:/tmp/mha.sh test socket
    2020-08-19 09:32:52,031 [uWSGIWorker1Core0:139922668804032] [mysqlha.views_os 19] [INFO]- done.
    Traceback (most recent call last):
    File "/usr/local/lib/python3.6/site-packages/django/core/handlers/wsgi.py", line 154, in call
    start_response(status, response_headers)
    OSError: headers already sent
    [pid: 24091|app: 0|req: 1/1] 10.107.68.57 () {48 vars in 817 bytes} [Wed Aug 19 09:32:49 2020] GET /mysqlha/test_socket_api => generated 25 bytes in 2080 msecs (HTTP/1.1 101) 4 headers in 184 bytes (0 switches on core 0)

[liu,guoshun]

similar to this issue : ​https://github.com/miguelgrinberg/Flask-SocketIO/issues/377

[Mariusz Felisiak]

Django itself doesn't support WebSockets.

Closing per TicketClosingReasons/UseSupportChannels.