I am currently developing a website where many users post topics and the associated topics' comments are shown in the page. Currently I'm developing using cake php.
The very first time a user clicks the website, all the topics and comments are displayed. But when other users add new topic or comment to a topic, I need to show the update in the same page. I am confused as in how am I able to retrieve new contents and update accordingly in a page. For instance how facebook does it where when your friends adds status or comments on your status, it updates without refreshing the page.
I know that AJAX technology is used but how is it done. Any source that I can refer? Hope someone can help as I have been doing research for the past one week but no answers so far.
You can go two routes in this.
Server Push
http://en.wikipedia.org/wiki/Push_technology
This technique is perhaps the most efficient as the server notifies the client of any updates. However this technique usually requires a bit more work than a simple polling system. You can use something like nodejs or Comet to push updates. If you're using nodejs, I highly recommend using SocketIO to handle the client side. With Socket.io you can have the client side listening to the server on a channel so that the server can notify the client whenever an update happens.
Client polls server
In this version, the client (new visitors browser) constantly polls the server for updates. You can set whatever gap you want, but keep in mind that if you make the polling gap too small your server might take a performance hit as each new user will create many requests. This method is as simple as setting up a setInterval() call in JS coupled with an AJAX call.
Related
I would like to create simple forum where users would be able to add/delete/modify posts stored in database. I have simple auth app: client(react app) - server(express). Is it possible to force client side to rerender for one user when there is a change made by another user while both are loggedIn?
It should be simple enough. When a logged in user is on a page that you want to keep synced, open a websocket to the server. Then, when any user makes a change, the server can update its database, and then once that's finished, it can send a websocket message to all users with connected sockets on that page, containing the new data to render.
In the client-side React, create the socket and subscribe to its message event. When a message is sent from the server, call the state setter with the new data.
This mechanism is somewhat similar to how Stack Overflow pushes "An edit has been made to this post" notifications when a post gets edited - anyone looking at the page will see such server-sent notifications through the websocket connection to Stack Exchange.
Websockets is one approach you can follow. If you think this will be complex to implement, you can poll for the data every minute or so.
This is very useful library tailored for React:
useQuery- https://tanstack.com/query/v4/docs/reference/useQuery?from=reactQueryV3&original=https://react-query-v3.tanstack.com/reference/useQuery
You can use it for polling/caching and making regular network calls as well. Lots of utility is provided that you can leverage; especially, considering the use case you seem to be tackling.
There is a slight learning curve, but its worth it if you're a react developer.
I am a beginner to web development, and I am trying to do a notification system with AJAX and jQuery.
In my web application, I have a comment system where you can mention another user. After a comment mentioning a certain user has been written, a new entry on my notifications table will be added, containing the comment, the id of the user who commented and the id of the user(s) who will receive the comment. After the notification is stored in the database, I want the person that was mentioned to receive the notification.
To that effect, I decided to use AJAX. Using the setTimeout() method, I am sending an AJAX request to the database every 2 seconds, and with that, I can display the notifications visually to the user that is meant to receive them.
My only concern is that this will slow down the site once I connect it with a server.
So, I was looking for a way that would allow me to implement a notifications system without slowing the site too much, since the one that I am using currently doesn't seem very efficient.
I would appreciate any help.
Hi so first I apologize if my query may seem unclear, it’s first trying to do what I’m doing and I haven’t full idea around the intricacies and lingo lol.
So basically I’m running a NodeJs web server with React handling my front end. I’ve got Express to help manipulate user sessions and I just came by Server-Sent-Events as a way to send one-way messages(which is what I need to do). So far I’m able to send updates and messages via cURL on the terminal and running JS scripts, however these updates/messages go to every active client session but I want/need to be able to send these messages to specific active client sessions/connections.
Example: 5 client connections are established (session IDs A,B,C,D,E), now I want to send an alert message to session E only and manually.
I’m still green with NodeJs/Express and the concept of SSEs however I’m learning as I go for this pet project.
Send help
What you want is how SSE works. It is a dedicated connection between a client and a server process.
however these updates/messages go to every active client session
If that is what you see then your node script is running the exact same code for each client.
I think your question might be higher up - how to organize the data messaging? That is too big a topic for a single StackOverflow question, because it will depend on so many factors specific to your use case.
But one way would be to have an SQL database, with one record for each user. The node script polls that database table and if the record for the current user changes, it sends the new data to them. Then to send data to user E, you just edit the database record for user E.
So I have developed a web app as a hobby on Handlebars, Express and Mongoose/MongoDB.
The app let's users create an account and then post advertisements for other users to see and respond to.
All the ads posted by users show up on the index page. So it is common view for all the users on this web app. I am relatively new to web development so to build such a simple app it took me a while but boy I learned a lot!
Now the issue I am facing is, when a user A posts an Ad while the user B is logged in and is currently on the index page (a page that lists all the ads posted) it won't show up for user B unless user B refreshes the page. Rightly so actually because only when the index page's route is hit it will query all the ads and refreshing is basically hitting the index route I get that. But I don't want it that way. I want it to show the new ad on user B's index and pretty much every user's index if there's new ad by any user.
So I did a little research/reading and I learned that I can do it by learning to work with triggers on mongodb and like create some kind of trigger that when a new ad is posted do something. I like the idea but failed to find resources to learn how to use such a thing.
The other option I was suggested was to use socket.io but that too I can't grasp how can I make an entire Ad document work as a socket. I am lost and implementing this feature of dynamically loading ads for all users will complete this hobby project of mine and will help me find a junior dev job in local community.
I request stackoverflow's community to guide me how do I go about doing this and what resources I can use to learn about it.
The socket.io seems to be the best solution for your case. What you will want to do with socket.io is every time a user posts an Ad you use socket.io to notify the rest of the users that there is an update.
If you don't want to send the entire document using the socket you can use the socket to notify the clients and on the client side every time you receive such a notice from the server you will either
a) Refresh the page(not suggested as it will make the user experience unpleasant) which is easier to implement
OR
b) You can use an Ajax request to get the new data from your server and update the fields on the fly(which makes for a better user experience).
Best Way You can come with using Short Polling concept from client side to ask for new data after 1 or 2 seconds (whatsoever count to need ) . Gmail for new inbox mails also uses sync method in a particular fashion . Just ask from server for new data
OR Second option to go through below
On Server Side
Serve index.html page to User A (which is logged in now).Some User B inserts data
Maintain a function or a cron job (checks the count of Total Ads ) Lets say after every 1 minute or so
If there is change in count from the previous total_count , update it and get new mlab documents and send it to function , Let's say push_new_ads which will be sync via socket.io to client
On Client Side
Sync your client_total_count with server_local_count push_new_ads using socket.io and If there is change in count , make a simple fetch api call to get data and appends it to previously fetched array
There is no such way to directly listen the changes in mongodb But you can trigger some changes from oplog using tailable cursors
I wrote a web page where there is a zone for user's comments.
Any authenticated users could post a comment.
As many users could post comments almost simultaneously, I want the comments list to be auto-refreshed.
Thus, I think about using WebSockets.
My thought are about a good/best practice for this use case:
Once a comment is posted, should WebSockets process read the current comments list on database and send a Json response containing all the new comments? This would allow the client to directly append the new comments on the DOM (JS).
Or should WebSocket just check the database (or queue if using a message queue (Redis, RabbitMQ etc..) for instance) and act just like: "Hey, I have new comments, click here if you want to see them !". This solution would only signal the presence of new comments, without bringing all those comments to the client. The workflow of retrieving the events would then involve by the client (by clicking on this sentence for instance) e.g using the traditional Ajax direction: client => server.
It is highly possible that a user posts a comment, then navigates to another page of the website. Therefore, a websocket response containing the whole new comments would be useless. A simple notification would then be possible, as most of known websites do for instance with the "+1" counter or more relevant to the "comments" scenario: "1 new comment available".
Which way should I choose?
I think to decide which data to push is mostly a matter of UI usability / user experience, as opposed to which technology is being used to interact with the server. We should avoid changing the UI with server pushed data in a way that would surprise the user in a negative way, for example having the comment feed constantly growing without any intervention from him.
But in the case of a realtime chart, it's probably better to push the data directly into the chart, that would be what the user expects.
In the case of the comment feed the reason why most sites go with the 'click to load' approach is because of user experience, so I think that is probably the best approach.
I use a combination of both....
In some pages the websocket communication contains the actual data--sort of like a stock ticker update.
And in other cases, the websocket communication just says -- all users viewing xyz data--refresh it. And then the browsers performs an ajax to obtain the new data and the grid is smartly refreshed in such a way that only the changed cells are modified on screen using innerHTML and the new rows are added and deleted rows are removed.
In cases like stackoverflow, it makes sense to show a message, "Got new stuff to show--want to see it?"
When I establish the websocket in the browser, I pass a page Id in the url and the cookies are passed too. So websocket server knows--the user cookie and the page which is being viewed.
Then in the database (or middle tier logic) communicates to the websocket server with messages such as: This message is for users viewing 'xyz' page: smartly refresh grid 'abc'. And the websocket server broadcasts the message.
Because the protocol allows you to pass anything you like, you have the ability to make it anyway you like.
My advise it to do what's best in each particular situation.