Flask-socketio: Monkey-patching ssl after ssl has already been imported may lead to errors

Created on 10 Apr 2019  Β·  8Comments  Β·  Source: miguelgrinberg/Flask-SocketIO

I am using Python-3.7 and Flask-SocketIO-3.3.2 on Ubuntu 19.04 (beta). I got the following message error while trying to execute python3.7 app.py:

MonkeyPatchWarning: Monkey-patching ssl after ssl has already been imported may lead to errors, including RecursionError on Python 3.6. It may also silently lead to incorrect behaviour on Python 3.7. Please monkey-patch earlier. See https://github.com/gevent/gevent/issues/1016.

In order to run the example app.py without any error message (on standard error) I did two things:

  1. Added two lines as first statements in file app.py to avoid gevent issue #1016

    #!/usr/bin/env python

import gevent.monkey
gevent.monkey.patch_all()

from threading import Lock
from flask import Flask, render_template, session, request
from flask_socketio import SocketIO, emit, join_room, leave_room, \
    close_room, rooms, disconnect

  2. Compared to requirements.txt I have updated the module six==1.12.0 and installed module gevent.

Using pipenv I provide below more details on dependencies:

$ python3.7 -m pipenv graph
Flask-Login==0.4.1
  - Flask [required: Any, installed: 0.12.4]
    - click [required: >=2.0, installed: 7.0]
    - itsdangerous [required: >=0.21, installed: 0.24]
    - Jinja2 [required: >=2.4, installed: 2.7.3]
      - markupsafe [required: Any, installed: 0.23]
    - Werkzeug [required: >=0.7, installed: 0.12.2]
Flask-Session==0.3.1
  - Flask [required: >=0.8, installed: 0.12.4]
    - click [required: >=2.0, installed: 7.0]
    - itsdangerous [required: >=0.21, installed: 0.24]
    - Jinja2 [required: >=2.4, installed: 2.7.3]
      - markupsafe [required: Any, installed: 0.23]
    - Werkzeug [required: >=0.7, installed: 0.12.2]
Flask-SocketIO==3.3.2
  - Flask [required: >=0.9, installed: 0.12.4]
    - click [required: >=2.0, installed: 7.0]
    - itsdangerous [required: >=0.21, installed: 0.24]
    - Jinja2 [required: >=2.4, installed: 2.7.3]
      - markupsafe [required: Any, installed: 0.23]
    - Werkzeug [required: >=0.7, installed: 0.12.2]
  - python-socketio [required: >=2.1.0,<4, installed: 3.1.2]
    - python-engineio [required: >=3.2.0, installed: 3.5.1]
      - six [required: >=1.9.0, installed: 1.12.0]
    - six [required: >=1.9.0, installed: 1.12.0]
gevent==1.4.0
  - greenlet [required: >=0.4.14, installed: 0.4.15]

$ python3.7 -m pipenv run pip freeze
Click==7.0
Flask==0.12.4
Flask-Login==0.4.1
Flask-Session==0.3.1
Flask-SocketIO==3.3.2
gevent==1.4.0
greenlet==0.4.15
itsdangerous==0.24
Jinja2==2.7.3
MarkupSafe==0.23
python-engineio==3.5.1
python-socketio==3.1.2
six==1.12.0
Werkzeug==0.12.2

$ cat Pipfile
[[source]]
name = "pypi"
url = "https://pypi.org/simple"
verify_ssl = true

[dev-packages]

[packages]
flask = "~=0.12.2"
flask-login = "~=0.4.0"
flask-session = "~=0.3.1"
flask-socketio = "~=3.3.2"
itsdangerous = "~=0.24"
jinja2 = "~=2.7.3"
markupsafe = "~=0.23"
werkzeug = "~=0.12.2"
gevent = "*"

[requires]
python_version = "3.7"
question
Source
picture olibre

Most helpful comment

the solution to this problem is to intall pyopenssl library

picture huihuiluyi on 26 Jul 2019
👍4

All 8 comments

Did you actually see the infinite recursion error? Because that happens when SSL is used. This application does not use SSL.

miguelgrinberg picture miguelgrinberg on 10 Apr 2019

Sorry, you are right.
I have removed my added lines about gevent.monkey and it works fine with the following:

$ cat Pipfile
[[source]]
name = "pypi"
url = "https://pypi.org/simple"
verify_ssl = true

[dev-packages]

[packages]
flask = "~=0.12.2"
flask-login = "~=0.4.0"
flask-session = "~=0.3.1"
flask-socketio = "~=3.3.2"
itsdangerous = "~=0.24"
jinja2 = "~=2.7.3"
markupsafe = "~=0.23"
werkzeug = "~=0.12.2"
# gevent = "*"
# gevent-websocket = "*"
# wsaccel = "*"
# ujson = "*"

[requires]
python_version = "3.7"

$ python3.7 -m pipenv run python3.7 app.py
 * Restarting with stat
 * Debugger is active!
 * Debugger PIN: 266-034-648

Played with localhost:5000 web page producing following output, then Ctrl + C.

Client disconnected 84c7130fcaed44f1a8bcb9171afe2762
^CKeyboardInterrupt
KeyboardInterrupt
2019-04-11T09:02:22Z
2019-04-11T09:02:22Z
olibre picture olibre on 11 Apr 2019

I did a complete test by first resetting my virtualenv:

$ python3.7 -m pipenv --rm
Removing virtualenv (/home/olibre/.local/share/virtualenvs/example-wxZDQ4eh)…

$ python3.7 -m pipenv --python 3.7
Creating a virtualenv for this project…
Pipfile: /home/olibre/dev/Flask-SocketIO/example/Pipfile
Using /usr/bin/python3.7m (3.7.3) to create virtualenv…
β ¦ Creating virtual environment...Using base prefix '/usr'
New python executable in /home/olibre/.local/share/virtualenvs/example-wxZDQ4eh/bin/python3.7m
Also creating executable in /home/olibre/.local/share/virtualenvs/example-wxZDQ4eh/bin/python
Installing setuptools, pip, wheel...
done.
Running virtualenv with interpreter /usr/bin/python3.7m
βœ” Successfully created virtual environment!
Virtualenv location: /home/olibre/.local/share/virtualenvs/example-wxZDQ4eh

$ python3.7 -m pipenv install
Installing dependencies from Pipfile.lock (e5ae1f)…
  🐍   β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰ 12/12 β€” 00:00:01
To activate this project's virtualenv, run pipenv shell.
Alternatively, run a command inside the virtualenv with pipenv run.

$ python3.7 -m pipenv graph
Flask-Login==0.4.1
  - Flask [required: Any, installed: 0.12.4]
    - click [required: >=2.0, installed: 7.0]
    - itsdangerous [required: >=0.21, installed: 0.24]
    - Jinja2 [required: >=2.4, installed: 2.7.3]
      - markupsafe [required: Any, installed: 0.23]
    - Werkzeug [required: >=0.7, installed: 0.12.2]
Flask-Session==0.3.1
  - Flask [required: >=0.8, installed: 0.12.4]
    - click [required: >=2.0, installed: 7.0]
    - itsdangerous [required: >=0.21, installed: 0.24]
    - Jinja2 [required: >=2.4, installed: 2.7.3]
      - markupsafe [required: Any, installed: 0.23]
    - Werkzeug [required: >=0.7, installed: 0.12.2]
Flask-SocketIO==3.3.2
  - Flask [required: >=0.9, installed: 0.12.4]
    - click [required: >=2.0, installed: 7.0]
    - itsdangerous [required: >=0.21, installed: 0.24]
    - Jinja2 [required: >=2.4, installed: 2.7.3]
      - markupsafe [required: Any, installed: 0.23]
    - Werkzeug [required: >=0.7, installed: 0.12.2]
  - python-socketio [required: >=2.1.0,<4, installed: 3.1.2]
    - python-engineio [required: >=3.2.0, installed: 3.5.1]
      - six [required: >=1.9.0, installed: 1.9.0]
    - six [required: >=1.9.0, installed: 1.9.0]

See below the warning about the missing module eventlet or modules gevent and gevent-websocket:

$ python3.7 -m pipenv run python3.7 app.py
WebSocket transport not available. Install eventlet or gevent and gevent-websocket for improved performance.
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
 * Restarting with stat
WebSocket transport not available. Install eventlet or gevent and gevent-websocket for improved performance.
 * Debugger is active!
 * Debugger PIN: 235-710-757
127.0.0.1 - - [11/Apr/2019 11:20:57] "GET / HTTP/1.1" 200 -
127.0.0.1 - - [11/Apr/2019 11:20:57] "GET /favicon.ico HTTP/1.1" 404 -
127.0.0.1 - - [11/Apr/2019 11:20:57] "GET /socket.io/?EIO=3&transport=polling&t=1554974457260-0 HTTP/1.1" 200 -
127.0.0.1 - - [11/Apr/2019 11:20:57] "POST /socket.io/?EIO=3&transport=polling&t=1554974457274-1&sid=086c507acedd4030afdc265b5fc2ba55 HTTP/1.1" 200 -
127.0.0.1 - - [11/Apr/2019 11:20:57] "GET /socket.io/?EIO=3&transport=polling&t=1554974457276-2&sid=086c507acedd4030afdc265b5fc2ba55 HTTP/1.1" 200 -
[...]
127.0.0.1 - - [11/Apr/2019 11:21:11] "POST /socket.io/?EIO=3&transport=polling&t=1554974471403-44&sid=086c507acedd4030afdc265b5fc2ba55 HTTP/1.1" 200 -
127.0.0.1 - - [11/Apr/2019 11:21:11] "GET /socket.io/?EIO=3&transport=polling&t=1554974471394-43&sid=086c507acedd4030afdc265b5fc2ba55 HTTP/1.1" 200 -
^C

Adding dependencies gevent and gevent-websocket:

$ vim Pipfile

$  python3.7 -m pipenv install
Pipfile.lock (f7a84d) out of date, updating to (e5ae1f)…
Locking [dev-packages] dependencies…
Locking [packages] dependencies…
βœ” Success!
Updated Pipfile.lock (f7a84d)!
Installing dependencies from Pipfile.lock (f7a84d)…
  🐍   β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰β–‰ 15/15 β€” 00:00:01
To activate this project's virtualenv, run pipenv shell.
Alternatively, run a command inside the virtualenv with pipenv run.

$ python3.7 -m pipenv graph
Flask-Login==0.4.1
  - Flask [required: Any, installed: 0.12.4]
    - click [required: >=2.0, installed: 7.0]
    - itsdangerous [required: >=0.21, installed: 0.24]
    - Jinja2 [required: >=2.4, installed: 2.7.3]
      - markupsafe [required: Any, installed: 0.23]
    - Werkzeug [required: >=0.7, installed: 0.12.2]
Flask-Session==0.3.1
  - Flask [required: >=0.8, installed: 0.12.4]
    - click [required: >=2.0, installed: 7.0]
    - itsdangerous [required: >=0.21, installed: 0.24]
    - Jinja2 [required: >=2.4, installed: 2.7.3]
      - markupsafe [required: Any, installed: 0.23]
    - Werkzeug [required: >=0.7, installed: 0.12.2]
Flask-SocketIO==3.3.2
  - Flask [required: >=0.9, installed: 0.12.4]
    - click [required: >=2.0, installed: 7.0]
    - itsdangerous [required: >=0.21, installed: 0.24]
    - Jinja2 [required: >=2.4, installed: 2.7.3]
      - markupsafe [required: Any, installed: 0.23]
    - Werkzeug [required: >=0.7, installed: 0.12.2]
  - python-socketio [required: >=2.1.0,<4, installed: 3.1.2]
    - python-engineio [required: >=3.2.0, installed: 3.5.1]
      - six [required: >=1.9.0, installed: 1.9.0]
    - six [required: >=1.9.0, installed: 1.9.0]
gevent-websocket==0.10.1
  - gevent [required: Any, installed: 1.4.0]
    - greenlet [required: >=0.4.14, installed: 0.4.15]

$ python3.7 -m pipenv run python3.7 app.py
 * Restarting with stat
 * Debugger is active!
 * Debugger PIN: 266-034-648
Client disconnected 274b91a2f487433c8396a0dd72512cfd
^CKeyboardInterrupt
KeyboardInterrupt
2019-04-11T09:32:56Z
2019-04-11T09:32:56Z
olibre picture olibre on 11 Apr 2019

@olibre can you clarify what is the issue that you are reporting? Is it the warning about eventlet/gevent missing? Because that is done on purpose, this package supports several web servers. The base installation uses the Flask development web server, you can then install a better one for production, and you have a lot of choices there: eventlet, gevent, gunicorn, uwsgi.

miguelgrinberg picture miguelgrinberg on 11 Apr 2019

Hi

TL DR: There is no issue, it works fine, I close the issue, thank you for your work :+1:

I had initially opened this issue because of the following error message:

Monkey-patching ssl after ssl has already been imported may lead to errors

After your first reply, I had re-checked and saw I was wrong. I said the following and closed the issue.

Sorry, you are right.
I have removed my added lines about gevent.monkey and it works fine

Finally I continued my testing and shared my results with you...
... but when submitting my comment I clicked on the wrong button and reopened the issue by mistake :-/

Cheers ;-)

olibre picture olibre on 11 Apr 2019

the solution to this problem is to intall pyopenssl library

huihuiluyi picture huihuiluyi on 26 Jul 2019
👍4

Thank you @PasserByYao πŸ‘

olibre picture olibre on 26 Jul 2019

Thank you @PasserByYao

mohanchug picture mohanchug on 9 Oct 2019
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