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!
Related
I am working with NodeJS and Cloudant (alternatively the DashDB Warehouse if that works better). I wonder if it is possible to have a function in NodeJS that gets called each time a document has been added to the database? I have checked out indexed views but can't really understand how to do it. Does anyone have any good tips regarding this or what documentation to look at?
You can listen to DB _changes in Cloudant (https://console.bluemix.net/docs/services/Cloudant/api/database.html) in continous mode.
Every document change in the Cloudant DB (create,update,delete) will be notified through this channel.
There are different nodejs libraries you can use with this purpose. This is
one example: https://www.npmjs.com/package/cloudant-follow
I am trying out React-Starter-Kit for the first time and loving all the cutting edge features baked in (apollo/graphql-client in particular). A crucial part of any app for me is the database, and for that my understanding is the same author provides nodejs-api-starter which sets up a REST interface for accessing Postgres at localhost:5000 and has a graphql webui at localhost:5000/graphl.
That is about as far as I have been able to understand of the setup so far. I have changed the frontend code a little bit so a new Component "Counter" is loaded on the home page. I need to be able to make a new counter, fetch the latest counter, and increment decrement the counter. Write now the component just outputs the 'value' retrieved from the server at 5000.
I do not think I am accessing the 5000 server correctly, do I put the port in this url line somehow?
You can pull the repo down from : https://github.com/Falieson/react-starter-kit-crud-counter-demo
This is my first time setting up a nodejs api server, I am used to using MeteorJS which has pub/sub to MongoDB baked in. I am looking forward to the separation the RSK strategy (which seems more industry standard?) provides.
I've just done setting up the full site with Database from React-Stater-Kit, I'm also a newbie so I understand your frustration.
About this question, you don't need the NodeJS-API-Starter, it has enhanced function ( such as Redis cache ) and it's not suited for newbies. You should look deeper into the RSK, it already has the DB. If you ran the boilerplate and played around, change is you'll see file database.sqlite in your folder, it's the database. Here are the things you should learn:
Use SequelizeJS to connect the NodeJS server with database. Your database can be MySQL/MariaDB, PostgreSQL or SQLite. The connection is easy and there's tool to auto-generate Models from your database
How to create GraphQL's Types and Queries. If your queries need to search through the database, import Sequelize's models and use its functions.
Test your API via GraphQLi
Note: if you want to use MongoDB or other NoSQL, try Mongoose instead of Sequelize.
I want to clone a public api into a mongodb database with nodejs so I can run my own queries and extend the data like I want. My problem is that I want to fetch the newest updates as well. The good thing is that I know when the data will change at the api app approximately.
I thought about something like cronjobs or a setInterval.
In the internet I could find many solutions how to transform a database into a rest api but no vice versa.
Please give me suggestions how to solve this problem.
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 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.