Support for web socket server

[nk sivaraju]

Hi, I need to push the data to the UI whenever something in the db changes. As this can be achieved  with web socket server, would like to know does py4web support web socket protocol? if yes is there any simple way to integrate ws server to the existing app? links to any examples would be more useful. Thanks in advance.

[Alexander Beskopilny]

ex1 (with internal py4web-tornado-server)
https://github.com/ali96343/py4web-chat

ex2 (with intermediate uvicorn-channel-server)
https://github.com/ali96343/lvsio

[nk sivaraju]

I want to achieve auto refresh in the UI dashboard. I wonder if there is any direct way of achieving it using Py4web . 

[Alexander Beskopilny]

ex3  (push data to user and update UI with celery and intermediate tornado-server)
 https://github.com/ali96343/capp

( it seems to me that the best solution is to use nodejs as an intermediate socketio channel-server )

[António Ramos]

why not a cloud service 

https://pusher.com

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[Alexander Beskopilny]

How to push event to js-UI from py4web controllers.py

small changes to  https://github.com/ali96343/lvsio

1 in controllers.py

https://github.com/ali96343/lvsio/blob/main/lvsio/controllers.py
----------------------------------------------------------

......
import socketio

@action("sio_pusher", method=["GET", "POST"])

def sio_pusher():

    import datetime

    data_str = datetime.datetime.now().strftime("%d.%m.%y %H:%M:%S")

    r_url = 'redis://'

    mgr = socketio.RedisManager(r_url, write_only=True)

    mgr.emit('frompydal',  data_str, broadcast=True, include_self=False )

    return f'sio_pusher {data_str}'

   

   # pip install httpie 

   #  http localhost:8000/lvsio/sio_pusher

.......

------------------------------------------------------------------

2  https://github.com/ali96343/lvsio/blob/main/lvsio/chan_3000.py

# ----------------------------------------------------------------

# pip install aioredis==1.3.1

r_url = "redis://"

mgr = socketio.AsyncRedisManager(r_url, write_only=False)

sio = socketio.AsyncServer(

    async_mode="asgi",

    client_manager=mgr,

    cors_allowed_origins="*",

    SameSite=None,

    logger=True,

    engineio_logger=True,

)

app = socketio.ASGIApp(sio, static_files={"/": "./public/index.html"})

# --------------------------- utils ----------------------------------------------

3 https://github.com/ali96343/lvsio/blob/main/lvsio/templates/sync_id.html

..................................

socket.on('connect', function() {

                socket.emit('sync_hello_connect', {data: 'from browser: connected!'});

                // console.log('sync connected')

            });

            socket.on('frompydal', function(msg) {

                console.log('frompydal !!!!!!!!!!!!!!!!!!!!!');

                console.log(msg);

            });

..................

--------------------------------
thats it

[Alexander Beskopilny]

how write  intermediate-channel-server 

Miguel Grinberg

Learn Socket.IO with Python and JavaScript in 90 Minutes!

[nk sivaraju]

I would like to know how can I integrate socket io with the py4web. I am going through socket io documentation (link to socket io server documentation) and found below line would do it.

app = socketio.WSGIApp(sio, app)                                                

But in py4web I don't know how to access the app instance. Is there any tutorial that shows how to integrate socket io with existing py4web app?

[Alexander Beskopilny]

Here's a working py4web-socketio-application
https://github.com/ali96343/lvsio

( The application is fully compliant with the python-socketio-documentation )

---------------

for string from your question app = socketio.WSGIApp(sio, app)

you can see lvsio equivalent 

in https://github.com/ali96343/lvsio/blob/main/lvsio/chan_3000.py 

r_url = "redis://"
r_mgr = socketio.AsyncRedisManager(r_url, write_only=False)

sio = socketio.AsyncServer(
async_mode="asgi",

client_manager=r_mgr,

cors_allowed_origins="*",
SameSite=None,
logger=True,
engineio_logger=True,
)
app = socketio.ASGIApp(sio, static_files={"/": "./public/index.html"})

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

it's equivalent for your question-string

------------------------------------------------------------------------------------------------------------------------

If you don't like the intermediate-channel-socketio server
you can integrate socketio-events into the internal-py4web-server

for "how to integrate" look into examples 

https://github.com/web2py/py4web/blob/master/py4web/utils/wsservers.py.txt

[Kevin Keller]

Thanks Alex, 

I have used the websocket server with py4web and it works great. 

Really appreciate you sharing this. 

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[Alexander Beskopilny]

To integrate the socketio (or websocket) into the py4web-app

pay attention to the data flow in the sio-ws-application

1. the py4web-controller sends an html page to the browser

 with the data from the pydal and the sio-connection-string-to-the-sio-server

2 the sio-server sends the data to a specific controller via POST request

(or via json-interface to pydal  bypassing the sio-server )

( The sio-server captures all sio-events-communication with the browser )

3 the py4web-wsgi-controller sends an event to  sio-server via redis connection _only_

( or sends the html-page to the browser bypassing the sio-server )

4 the py4web-controller and the sio-server can also communicate

through additional redis channels with py4web-controllers-fixture

( fixture example https://github.com/ali96343/py4web-chat/blob/main/chat/remeutils.py )

-----------------------------------------

5 it is also convenient to use the socketio to interact with the celery

6 The main source of information about the socketio is Miguel Grinberg 

[Kevin Keller]

This is super cool!! 

Thanks again. 

I had another thought though, how hard would it be to make ombott (our bottle replacement) async using and runig with e.g. uvicorn?

Would that not also simplify our 2 server architecture? 

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[Alexander Beskopilny]

(sorry for typo in sentence 2 in prev-post , it should be - (or via json-interface to pydal )     )

Thanks for the question.

It seems to me that by running py4web,  redis,  celery,  sio-channel-server under 

monitors  (monit, daemontools, etc...) we can have a very usable
analog of  the  erlang machine.

Also, I think it is very difficult to integrate multiple events
of many py4web-applications into one server. 

It is much easier to have independent-sio-channel-server for each py4web-app

of course it is possible to replace sio-uvicorn-channel with other servers - tornado or nodejs .....

( for me, well tested py4web-threading  ,
much better than experimenting with python-async-await ... etc    )