I have a website which can have up to 500 concurrent viewers, with data updated every three seconds. Currently each user has an AJAX object which calls a web-page every three seconds which queries a DB and returns with the results.
What I would love to do is have each client get a socket to a node.js object, this node.js would poll the DB every 3 seconds for updated data, if it had updated data it would then be announced (ideally through JSON) and each client would then have the data pushed to it and update the page accordingly.
If this is possible, does anyone have a recommendation as to where I start? I am fairly familiar with JS but node.js seems to confuse me.
Thanks
I myself have quite few experience with node.js.
It is absolutely doable and looks like the perfect use case for node.js.
I recommend starting with an Express Tutorial and later on use socket.io.
I don't know which DBMS you are using, but there probably is a nice package for that as well. Just look through this list.
Related
I want to develop an attendance management page where I want to update my MongoDB database every time when the user leaves the page.
I found unload function in some answers, but cannot realize how to use it in Node.js.
How can I do this using Node.js framework in PhpStorm?
You would have to do it from server side, sending request from client before he leaves the page is a bad approach. There are many ways how client can disconnect without sending any request, like connection lost, killing process etc.
Maybe consider different approach, like sending an ajax request as an indication that user is still on page?
Or you could look around for existing solutions, maybe something like Using node.js to display number of current users
could help.
I have an nodejs server running witch show data on a web interface. The data is fetched from a MongoDB using mongoose. The data is added via an node-red application witch is isolated from the rest.
Currently my nodejs server fetches the data every 5 seconds. Is there a way to know if the data in my MongoDB has changed?
Thanks, I hope my question is clear.
I was also looking for something similar to what you are asking for few months back. Few ways which i know to do it are:
1) You can try to use middlewares while inserting your documents in DB. You can then send that new data either after saving it in DB or at the time of insertion only.
2) Refer to this answer which talks about solving your problem using inbuilt functions provided by mongoDb. You can study in deep about them in mongoDb docs.
3) There is also another way to do this which includes listening to changes in log files. As you know everything done in mongo is recorded and logged in files so whenever there is some change in data you can know it from there also. You will have to do the digging by yourself in this method.
Hope it helps!
I am working on a small hobby project, where I would really like some input and advice.
This is my first "real" node project, and I hope it will teach me a lot about node.js development. I am a .net developer by day, and have been for about 15 years professionally. I have had periods of doing Java as well. I have created small node.js projects to be used as micro services.
But this project can no longer be classified as a micro service ;-)
The purpose of the project is to sample some sensor data, and do some reporting. An idea I got from playing around with a PLC at university. I do that by sampling from a PLC, and emitting the data using ZeroMQ. My node.js server then listens for this sensor data, and stores it in a MongoDB.
I expose that data in a REST api. The REST api also exposes resources like batches and other stuff like authentication etc. On top of that I have an AngularJS app, that creates defines the UI.
The one thing that really annoys me, is that I want to globally assign what batch is running. I have a collection of batches, and one of them is the running one. There are a two ways I see to do this, and both illustrate my novice status in the node.js world. All users should be able to see what batch is running, and I want to be able to easily tell from anywhere in the code as well.
1) Set a flag on the object in Mongo. This has a number of problems. The obvious one being performance. I receive sensor data 10 times a second, and I don't want to ask the database every time what batch to save it under.
2) Save the info on the global object. I really don't like this either. I don't like global state in my code.
What is a good pattern for doing something like this? Does my question make any sense?
Thanks in advance
You can make a simple REST call to set the active batch and call it inside the batch when is started up and ready to accept requests. For example:
app.put('/active-batch', function(req, res, next){
// Make sure req.body is defined
app.set('active-batch', req.body);
res.end();
});
Then everywhere in the code you can use:
app.get('active-batch');
The app.set let you save data globally accessible in your app and app.get let you read previously stored data.
I just started using node, backbone and mongoose not so long ago to create my first web app.
At the very beginning, I followed tutorials, and used backbone client side to define models. Those models mirror my mongoose schemas server side.
When I run schema.save() on one of my models, my data is automatically sent back to the client, with an _id.
But now that my app is almost finished, I realize that I don´t really need to save anything, as the only thing I do is query an api, and the data doesn´t have to be reused.
So my question is, what is the best way to keep the same mechanisms, but without saving anything?
The end reason is that I plan to run the app on an ec2 instance, and knowing that I don´t need to save anything, I think it is more beneficial to reduce the IO usage by not having any database.
Thanks, and sorry if the question seems dumb.
I have a small Node.js HTTP server that does requests to a mongo database (with the mongoose module).
What I want to do is query the database, store it in a variable (array) and send it to the client.
Because ideally, when the user clicks on one of the buttons on the html page, the JavaScript will pick-up the event and change the appearance of the website by showing calculations based on data that is stored in the database.
The only way I could come with was just "transferring" the database content to the client browser but if anyone can come with another solution that would be fine too !
So basically my question is :
How can I pass a variable from the Node.js server to the client browser when serving a page ?
Thank you in advance !
If you will be doing more than a couple of these types of transfers, I recommend looking into Socket.IO.
It's a layer that provides quick and easy communication between Node.js servers and web front-ends, by abstracting web sockets when available, and falling back to other transports (such as JSON-P or Flash) when it's not available. Basically, you would call io.emit('something', {yourdata: here}), and it is easily received on the other end. All of the serialization is done for you.
http://socket.io/
Give their demo a shot to see how it works.