I'm searching for a framework capable of subscribing to live updates on a paginated list.
The server should take into account the users query for that subscription, and should only send the updates to the subscribers that passes the query instead of broadcasting to everyone.
Is this possible to implement in deepstream.io, and how hard and efficient is it?
I've been using Meteor for this, but I'm trying to deviate from this stack.
Thanks.
Using deepstream in conjunction with RethinkDb should do the trick. Have a look at the official RethinkDb search provider (https://github.com/hoxton-one/deepstream.io-provider-search-rethinkdb) which already creates dynamic lists based on queries. Adding pagination to it should be reasonably straight forward.
Related
Let's say, hypothetically, I am working on a website which provides live score updates for sporting fixtures.
A script checks an external API for updates every few seconds. If there is a new update, the information is saved to a database, and then pushed out to the user.
When a new user accesses the website, a script queries the database and populates the page with all the information ingested so far.
I am using socket.io to push live updates. However, when someone is accessing the page for the first time, I have a couple of options:
I could use the existing socket.io infrastructure to populate the page
I could request the information when routing the user, pass it into res.render() as an argument and render the data using, for example, Pug.
In this circumstance, my instinct would be to utilise the existing socket.io infrastructure; purely because it would save me writing additional code. However, I am curious to know whether there are any other reasons for, or against, using either approach. For example, would it be more performant to render the data, initially, using one approach or the other?
I'm relatively new to webdevelopment and have been using ArangoDB for most of that limited experience. I have a basic understanding of Node.js and creating express based CRUD apps with ArangoDB as the database.
I'm getting to a point though where I'd like to have the ability to query the database from inside the client. Say I would like to have a datalist-type element where the user types words into a searchbar. I'd like the ability to query the database from there rather than having to query the database for all of its files prior to creating the datalist. I have not found a single mention though of using database queries from the client side. I can't imagine that this is not possible. Surely when I search wikipedia through the search bar and it provides me with options I didn't just receive the entire wikipedia documents list upon loading the page? Please steer me in the right direction, I don't know how to tackle this problem.
Have a look at how to build dynamic forms, this will allow you to perform AJAX style calls from the browser window to a back end REST API service. This will allow your back end web service to gather the data for the response (from ArangoDB if required), and respond with that data, most likely in a JSON format.
Your UI can then take that response and dynamically update components in your DOM so that the user can see the data injected into the page without a page reload action taking place.
https://www.pluralsight.com/search?q=ajax is a great place to start.
Alternatively you can have a look at free content like https://www.youtube.com/watch?v=tNKD0kfel6o
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
We've got an application in Django running against a PGSQL database. One of the functions we've grown to support is real-time messaging to our UI when data is updated in the backend DB.
So... for example we show the contents of a customer table in our UI, as records are added/removed/updated from the backend customer DB table we echo those updates to our UI in real-time via some redis/socket.io/node.js magic.
Currently we've rolled our own solution for this entire thing using overloaded save() methods on the Django table models. That actually works pretty well for our current functions but as tables continue to grow into GB's of data, it is starting to slow down on some larger tables as our engine digs through the current 'subscribed' UI's and messages out appropriately which updates are needed as which clients.
Curious what other options might exist here. I believe MongoDB and other no-sql type engines support some constructs like this out of the box but I'm not finding an exact hit when Googling for better solutions.
Currently we've rolled our own solution for this entire thing using
overloaded save() methods on the Django table models.
Instead of working on the app level you might want to work on the lower, database level.
Add a PostgreSQL trigger after row insertion, and use pg_notify to notify external apps of the change.
Then in NodeJS:
var PGPubsub = require('pg-pubsub');
var pubsubInstance = new PGPubsub('postgres://username#localhost/tablename');
pubsubInstance.addChannel('channelName', function (channelPayload) {
// Handle the notification and its payload
// If the payload was JSON it has already been parsed for you
});
See that and that.
And you will be able to to the same in Python https://pypi.python.org/pypi/pgpubsub/0.0.2.
Finally, you might want to use data-partitioning in PostgreSQL. Long story short, PostgreSQL has already everything you need :)
I'm researching BreezeJS for a big upcoming project.
Our goal is a offline first web app.
But here is what I can't fully understand (and would take to much time to test) - Does BreezeJS allow for the backend to be a REST API (built with NodeJS and Express)?
We need this because we don't want to simply sync to a remote DB (in our case Mongo), but use a remote REST API so that we can embed some business logic. Things like workflow triggering on a POST to a particular entity.
Is this possible with BreezeJS? If not what would be a good option?
Thanks in advance
It is certainly possible, simply take the breeze-mongo server implementation and strip out the mongo specific code. This should be fairly straight forward, express and mongo are pretty well separated in the code.
That said, you would lose or have to rewrite much of the server side code that converts an OData query string into a mongo query, but if you are going pure 'REST' you probably don't want that anyway.
You would have to do something similar on the save/POST side, but this is presumably something you are already familiar with.