so currently i am studying web development but the course was a little bit confusing, the teacher starts explain promise object and fetch then axios, after that he starts to talk about the "express" package to build server side, and am asking myself what is the different between using API objects & building server side using express?
Both of those things work together to create a website/app. axios, etc runs in the browser (client-side code), and is used to send requests to the server (express/other server-side code), allowing the server to fetch data, or modify the database, and return a response back to the browser side code, which continues operating from there.
imagine, client-side code does not have access to your server's database, as your database is on the server, and the browser is on the end user's computer. The two sets of code send messages back and forth to each other to create an app that has a centrally stored data store that is "shared" between users.
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I recently learned about webhooks and am trying to implement one for a full-stack app that I'm building. However, I haven't been able to find information on how to create my own webhook. This is how my app is expected to work:
My client side is a website built with React, and when it loads, it will make a GET request to my server (built with Node and Express). The response will provide data that will be displayed on the website. The user will click a button on the website, which will send a (POST? GET?) request to my server, which will make its own POST request to send some of the data to an external API. When that external API data completes work on the data, it will send a POST request to my webhook URL (which I assume is part of my server), and the data from the external API needs to be sent to the client, which will display it alongside the original data. Additionally, when work on the first batch of data is completed, my server sends another POST request (with some more of the original data) to the external API, which will then make a POST request to my webhook/server with new data that then gets passed to the client again, and this repeats until all the original data from my server has been passed to and processed by the external API, and the all the processed data gets sent to my server and then to the client.
From my understanding, the webhook will allow my client to make a single request to my server, and then, my server can make multiple response to my client: one response for each POST request received from the external API. However, I have not been able to find information on how to create a webhook. Everything that I have found has been about how to use webhooks with pre-existing apps/websites like Dischord or GitHub or Stripe. Or using 3rd-party services to use their webhooks to connect pre-existing app/websites.
How do I go about making a webhook for my little project that will update my website every time that my server receives a POST request from the external API? Or am I misunderstanding how a webhook works? Can they only be created by 3rd-party services and/or only used on pre-existing apps?
For a simple use case, it just means another endpoint on your server that will receive a request from the external API when it's done with the task. It's a common way REST APIs work to let you know they are done with something, or communicate anything back to you in general. You have one endpoint that will receive a request from the React client, and send information off to the external API (as you said), and another endpoint (this "webhook") that will receive requests from the external API. That's it.
You described the client-server communications for this problem just fine with the exception that the server cannot send requests to the client over HTTP. If the client needs anything from the server, it needs to send a request and ask for it. A common way to do for this would be to store the information on the server once the external API hits your "webhook", and the client can ask the server if the data is back every X seconds (long-polling).
Example (payment flow):
Client -> Server: Heres my credit card number
Server -> Client: Thanks! Let me process that.
Server -> External API: Please process this credit card for the amount of $X and ping me at this webhook when you're done.
External API -> Server: OK, will let you know when I'm done.
Client -> Server: You done yet?
Server -> Client: Nope!
External API -> Server (to webhook): Hey, I'm done, here's the receipt.
Server -> External API: Thanks!
Client -> Server: You done yet?
Server -> Client: Yes! Here's your receipt.
More advanced ways to solve the problem would be using a long-lived bidirectional communication protocol such as websockets. And as others have mentioned, all of the endpoints don't have to be on the same server. You can have one server for each endpoint, and you can have turn them on only when they get a request and then go back to sleep (that's a Lambda). Pros and cons to this approach. That's more advanced stuff and if you're just learning I wouldn't really worry about it now.
AFAIK, webhooks are just normal web APIs. Properties that make an API a webhook:
The client sending requests to your server, in this case, is another server
This client will send you a request when there's a triggered event
In your case, your server POSTing data to the external API. What makes webhook different is that the external API's server doesn't have to respond right away, instead, it sends back you, for example, an HTTP 200 OK to acknowledge that it received the request and has started to process the data. When the external API's server finishes processing the data (which is an event), it will call your server's endpoint to inform you about the process along with the processed data (if succeeded).
Your server, correspondingly, will then have to inform your client (the user) about the processed data. I would suggest implementing some kinds of persistent connection (WebSocket or SSE), or simply just make the client poll request every some second.
"(which I assume is part of my server)"-- The webhook is part of the third party API that points back to either your server or maybe some serverless function/lambda(that you set up) that in turn can parse and perform computations on the data and then send it back to your server.
It really depends on the use case and architecture of your API. If you don't want your main API server to get overloaded, if say you need to perform heavy I/O, CPU/GPU processing, you could create Serverless Lambda Functions to handle this data processing and be the endpoint you supply to the third party's webhook post endpoint.
If you're not concerned with it, you could just create another endpoint in your server to handle this webhook.
Just keep in mind, when you're trying to scale up, you want your systems to be as distributed as possible-- within reason-- so your API can handle more requests and not be overloaded with a bunch of processes.
I have an Apache server A set up that currently hosts a webpage of a bar chart (using Chart.js). This data is currently pulled from a local SQLite database every couple seconds, and the web chart is updated.
I now want to use a separate server B on a Raspberry Pi to send data to the server to be used for the chart, rather than using the database on server A.
So one server sends a file to another server, which somehow realises this and accepts it and processes it.
The data can either be sent and placed into the current SQLite database, or bypass the database and have the chart update directly from the Pi's sent information.
I have come across HTTP Post requests, but not sure if that's what I need or quite how to implement it.
I have managed to get the Pi to simply host a json file (viewable from the external ip address) and pull the data from that with a simple requests.get('ip_address/json_file') in Python, but this doesn't seem like the most robust or secure solution.
Any help with what I should be using much appreciated, thanks!
Maybe I didn't quite understand your request but this is the solution I imagined:
You create a Frontend with WebSocket support that connects to Server A
Server B (the one running on the raspberry) sends a POST request
with the JSON to Server A
Server A accepts the JSON and sends it to all clients connected with the WebSocket protocol
Server B ----> Server A <----> Frontend
This way you do not expose your Raspberry directly and every request made by the Frontend goes only to Server A.
To provide a better user experience you could also create a GET endpoint on Server A to retrieve the latest received JSON, so that when the user loads the Frontend for the first time it calls that endpoint and even if the Raspberry has yet to update the data at least the user can have an insight of the latest available data.
I have a chat application, backend is written with help of Socket.io (based on Node.js server), and client is pure vanilla JavaScript, with JWT token generation from PHP, chat loads all data on load from REST API written on PHP also, and i am stuck with file upload.
I have two variants, first is REST API, just send data with help of XMLHTTPRequest, and i already implemented this, it's a simple FormData POST to REST,
it works fine, but i am not sure of "rightness" of this solution, because for now REST have only GET routes for simple users (there is admin routes also) and by design of my project, it's set to get data for user chat, and its looks not right for me to make POST route for them, but what worries me most is what i already have another mechanism/solution where user sending their messages, it is socket.io-node.js server, with all permission checks (does this user have permission to join this chat, send information to it, and so on), so REST will take part of Socket.io task. Also beside role distribution problem, REST solution is also a logic duplication, where all permission checks written on Node.js side, must be duplicated on PHP side. As a result i already started to rewrite file sending to Node.js via Socket.io. Socket.io from version 1 is accepting binary data, so it's was pretty easy, i just sending a File and Node.js gets Buffer, which is easily stored to filesystem like this
require('fs').writeFileSync(filePath, Buffer);
but here i have problem what i don't have upload progress, and most importantly despite all projects part are now perfectly distributed by their roles (client is sending data to socket.io, and reads from rest), and i have no role duplication, i am still not 100% sure i solved this problem right.
So question is, how and where would you send your files, in case of your chat application.
I am making a web-app using JavaScript. I plan to use Node.js to connect the app to an existing MySQL database.
First of all, will the Node code be written in the same .js file as my application? Or is it a separate file?
I need the data to be current at all times (even if you were to close the browser and re-open it, AND even in the event of the user not having a wifi connection), so my thought was to constantly update the local device's db and then to intermittently update the MySQL db. Is this the best strategy? If so, how exactly can Node talk to the offline db and MySQL?
First of all, will the Node code be written in the same .js file as my application? Or is it a separate file?
It is possible to keep your client side JavaScript in the same file as your server side JavaScript, but it doesn't make any sense to do so. They are separate programs. (Library files, on the other hand, are a different story).
so my thought was to constantly update the local device's db and then to intermittently update the MySQL db.
Working with a local database and syncing to a shared one is a common strategy. You do need to handle conflicting updates in a way that is sensible for your purposes though.
If so, how exactly can Node talk to the offline db and MySQL?
Node.js can't talk to the offline database, at least not directly.
You will have a web application running in the browser. It will use client side JavaScript with a client side database and some means of communicating with the server (often this is done by sending JSON over HTTP to and from a web service).
Then you will have a server side application running in Node.js. It will use server side JavaScript with a server side MySQL database and some means of communicating with the client (i.e. an HTTP server hosting a web service).
The case is quite straight forward (in my mind). The client has a native application running on his machine that produces pairs of values. What I am trying to accomplish is when this service is running and the user visits my web service I want to be able to retrieve these pairs of values with JavaScript code on the clients browser. I haven't decided because I am not sure what kind of server should create the pairs or how to grap them with JS. I have tried using pubnub to setup a channel of communication but the round trips are kind of slow.
Any suggestions?
You could access a local http server (LAMP / WAMP) for AJAX calls with javascript via the 127.0.0.1 or localhost addresses.