Django refresh page if change data by other user - django

I have a test django app.
In one page the test show the same question to all users.
I'd like that when a user answers correctly, send a signal to other active user's browser to refresh to the next question.
I have been learning about signals in django I learning work with them but I don't now how send the "refresh signal" to client browser.
I think that it can do with a javascript code that check if a certain value (actual question) change and if change reload the page but I don't know this language and the information that I find was confused.
Can anybody help me?
Many Thanks.

There is no existing way to send a event from server to browser. But you can get your web page polling your server periodically (say every 5 seconds).
The code in javascript/jquery could be like the following
setInterval(function(){
$.post("your_ajax_handler_url/is_answerd", userId, function(xhr){
if(xhr.responseText == "answered"){
location.reload(true);
}
}
}, 5000);

That is not at all what signals in Django are for. Signals in django are server side hooks that allow you perform tasks on the server when a certain even happens.
To 'send a refresh' to the browser, you need to use a server-push approach such as Comet. Alternatively you can get your clients to periodically poll the server to look for update.
Here's some links:
How to implement Server push / long polling / comet using PHP and Javascript
How do I implement basic "Long Polling"?

What you need are coment(http://en.wikipedia.org/wiki/Comet_%28programming%29) and tornado(http://www.tornadoweb.org/)

Related

Refresh a page when something new appears in Django

I'm creating a website for a local establishment that uses Ifood. Ifood provides an API that allows you to check information, both regarding establishments and incoming orders.
The code is ready, but I can only show a new order update when manually refreshing the page. Which is a bit shippable. I thought about putting an automatic update with JavaScript at the given time, but it would be an ugly workaround.
In this case, I'm getting JSON data, but in a more general context.
How could I refresh the page as soon as new data appears?
An automatic update with Javascript might not be as dirty as you think. Even smartphone push notifications are really just occasionally polling under the hood.
If you really want to push from your server, WebSockets or server-side events are what you want. Unfortunately, it seems this kind of setup is not natively supported by Django.
Another option could be to use a paid service like Pusher.com. Such services usually let you listen for an even in JS, then call an API endpoint to trigger it from your server. This will work well on Django or any other server setup.

How to use django signals to refresh a specific page

I am creating an ecommerce webapp and I want to update my admin page when user place order. After research i found out about Django signals, but it seems pretty confusing. The idea behind this is that, when a user places an order I want the admin page to be refreshed and show the latest updates. I tried ajax but javascript can only work with the current open page. Can anyone help me with usibg django signals this way?
I think you misunderstand a little, if your idea is that the admin page viewed by the user in a browser is to be refreshed. The page viewed by a site visitor is retrieved on demand of the browser. The user could refresh a page, or a page script may auto-refresh on a timer (this is not a very good solution, but it is easy).
Django can't make the browser update the page.
Signals can cause django to do something in the backend, but they can't solve the problem that the browser is in charge.
There is one technology designed to allow the server to push content to the browser: websockets.
If you use websockets (Django's fairly recent built-in support is called Channels (https://channels.readthedocs.io/en/stable/)), then you can push content to the browser, where a receiving script on the page will do something with it. This is a very powerful technique, but there is a learning curve of some hours if you are starting from scratch.
Recently I came across this front-end library which tries to make this easy as
far as the browser goes: https://htmx.org/docs/
But you still have to deal with running a websocket server and learning how to send messages to a websocket. You will however feel like a superhero at the end of it, so there's that.

Is there a way to send push notifications with Django

Hello I wonder is there a way to send push notifications with Django to a user.
I have a website that accepts/refuses vacation demands.
When a user sends a vacation demand my Django app sends email to the CEO to notify him that there was a new vacation request.
When the CEO accepts the demand it sends email to the user that the demand was accepted.
But since the CEO receives plenty of emails a day and he barely sees my emails i would like to make a browser notification whenever he opens the browser to see notification from my website that a demand is waiting to be approved/refused.
Is there a library that can do that for me,
I've tried django-webpush but I couldn't managed it to work even though I
followed all the steps.
Yes you can, since your have the information that your user accessed your server at least once. checkout this lib
https://github.com/jazzband/django-push-notifications
EDIT Gonna put more information about it
If you expect receive one response from your backend to your backend you can write some watcher to receive new data, or create one plugin, or use sockets or even make your frontend send one call to backend with some interval time to check if there is any new messages...
Lets split up a bit
1 - Watcher
Using watchers you can just watch your backend to any changes... build it from scratch i thing i a bit "hard", you can use some modern frontend framework that already have it like Angular, React, Vue... and capture new incomes messages from your backend and create Notification instance in your browser and your it to your user (i guess they will have to keep the page openned to do it... im not 100% sure)
2 - Plugins
You can build one plugin to add to your browser and receive the data from your server... since you already in browser is more easier to use browser functions
3 - Sockets
The common way to make 2 ways comunication from frontend to backend, most used with chats and things arround that, just create one channel of communications between this 2 sides and you will be able to send and receive messages from frontend or backend
4 - Dirty Way
If you not get the time to implement it like supposed to do with quality you can go the dirty way, just setup one ajax in your page to check your backend to new messages every 5 minutes? or more or less... and if find any new data (of course you will have to handle it on your backend like any other suggestions above) and then you create one new notification in your browser and show to your user...
Im sure there is bunch of libs that already do most of things to you, so just search a bit and test until you find anything that fits your need

Send a post request to server

I am fairly new in web development and I decided to handle a user's availability to send a POST request to server. However, I do not know even whether it is possible or not but when a user close my Django site without using logout button (For example close the browser or tab), in order to understand the user is offline or online, I want to send a request to server. As a result, when the server does not get an answer from the user for a while, it automatically logout the user.
Can you tell me is it a good way to handle a user's availability and first of all is it a realistic solution? If it is, can you suggest me a document or example that helps me please.
I agree to to the answer of #Mounir. That's not related to django, if you want to know when a user is "disconnected"(close the tab or window) you need to use javascript, in concrete you need to use Sockets.
I recommend you this ones:
http://socket.io/
https://github.com/centrifugal/centrifugo
I'm using centrifugo for one project right now. In concrete, for chat and inbox messaging. It's very simple to make it run with Django.
Greetings
For logging out user you can use the Session expiration, but for all other staff you want to achieve I don't see any thin really related to Django itself, everything depend on your requirements and is more Browser/javascript related than Django.

Interact with web browser using Qt/bash script?

I frequently need to access to the router to do some simple task: restart, switch on/off some options... And the repeated process really annoying me :(
I want to write a batch script/program which do it for me.
I can't flash the router with the DD-WRT firmware to access it via console. The policy don't allow it.
Then I come up with an idea that use Qt write a small program which will interact with the browser. Access the router IP, fill the password, browse to the option page...
However, AFAIK, I can only do such thing with a web-driver like selenium, which is unavailable with Qt.
So is there any solution? I really like the idea use Qt or a script to solve the problem.
Any ideas are appreciated :)
It is possible to just send form response and don't load the page in the QWebFrame. You can use some tool (firebug, wireshark) to catch the request/response when you click "save" and learn what to send to your router everytime you want this configuration. It will be simple HTTP GET or POST request. That request can be done with curl, wget or your simple QT application using QNetworkRequest or wethewer.
It will be more tricky if it needs authentification other then HTTP basic auth. You will need two requests
first one - authenticate and save all cookies
second one - set parameters and add all cookies to response