Server-Sent Events with NestJS 

Well an engineer he is 😅. Good video!

Another lovely video Marius, being follow your nest tutorials and you have really been helpful.

Hello @Marius can you explain deployment of NestJs app with TypeORM-MySql database from scratch because I'm stuck at the production. Please provide one video from scratch which basically includes NestJs MySQL and TypeORM deployment.

There’s definitely ways you can identify the client, like some ideas here: stackoverflow.com/questions/34992442/how-server-sent-event-send-response-to-a-specific-client If you’re authenticating users you can set a cookie that determines their session id, that should come along with the request. If you’d like to make a comparison with the setup for nest specifically, I do have a websockets video with Nest in the channel

@@mariusespejo Thank you so much for your time and link, i'll take a look

Thank you!! Deployment is a large topic but definitely thinking of ways to incorporate it in the channel

@@mariusespejo Thanks, it would be really helpful to many us with deployment video. Please make incorporate to this channel :)

Thanks! I think just the standard font? I don’t remember changing it

Thank you! Glad you like it

Yeah pretty much to match the spec, if you read about it under the hood what’s really being sent by NestJS is something that looks like this: developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events#examples Which you’ll notice pretty much it makes you assume the payload of the event is generally either a basic string or an object.

@@mariusespejo Thanks mate. So far I have been following along with your tutorials and I really love NestJS, for the most :) But I have to create an API with is going to handle a large amount of data, sometimes I will have to recieve a lot of data, transform it and inserting between 1K-10K rows in a database. Do you think NestJS with TypeORM could handle that? Or woulda .NET Core API with React on top of it be a better solution for this?

nestjs and typeorm are just frameworks/libraries. On their own they don’t determine what can or can’t be handled based on load, that sounds like a question more for your infrastructure… e.g. are you thinking about scalability… does your infrastructure allow spinning up additional instances of the server when one can’t handle all the requests… does your database handle multiple concurrent writes, etc. etc. In general what is “better” can be very subjective. There’s a lot of variables at play including ecosystems… if you can’t decide I suggest doing a proof of concept with your top options and go from there

@@mariusespejo Thanks once again for the thorouw reply Marius! I guess what I was thinking about the most is that I would be afraid that Node/Nestjs would be blocking incommin requests to while the application was inserting ~10K rows in the database and at some point it would fail. The whole infrastructure and scalability taken care of and it should be fairly easy to scale horizontally, however I would love if I didn't have to do so in order to keep the cost low. But I will probably end up trying to make two small demos with a lot of inserts to test the performance. Thanks

I highly recommend reading about the event loop and how it works. I think a lot of people assume “oh it’s single thread so long tasks are blocking” it’s not really that simple. E.g. from my understanding database IO is an asynchronous event and should be non-blocking. If you’re having to transform that data synchronously before or after inserting to the database, that probably is blocking however how much that becomes a problem depends on your underlying algorithm. Also you can setup your API to not necessarily wait for the entire thing to be done before responding… you could take an event-driven approach. In general I think that NodeJS scales fairly well if used properly, even on a single server. nodejs.org/en/docs/guides/blocking-vs-non-blocking/

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Depends on the mobile browser itself if it supports the client api or not

I think so, I don’t see any problems with that. You’re really just defining separate routes, and if one happens to be for SSE I think it should be fine

Yes… it’s a beginner tutorial. You can take a look at this package as one way to consume sqs www.npmjs.com/package/@ssut/nestjs-sqs

Using the EventSource API as mentioned and shown in the video.

Yes, should work in any framework

It’s up to you what event you trigger so yes

I would imagine it’s not really about queueing at all, … I imagine you have some kind of store for the cache? Then your store just needs to be updated to cache the response of the first request… then any requests made after that simply needs to first check if the value is in the store and if not then it must be the first request. If you really want to try some kind of waiting/queue behavior I imagine you can use locks to pull that off. E.g. if data not in cache, acquire lock and fetch data, store data in cache. If data not in cache and unable to acquire lock, just wait (it means another request already initiated)

@@mariusespejo the main purpose is caching n storing ,but when concurrent requests are made ,node is async so all will try to contact db,though I write any check to get the value from cache. How could I avoid load at db. First request to that api need to contact db and other requests need to be queued until I get response from first request then i will cache the value ,later i will pass requests in the queue which can get the values from cache as we are writing a check logic in the beginning

@@mariusespejo i know my question is not related to the video,but i thought u have that exposure to resolve the issues,as your nestjs videos are so informative n precise n smooth to follow up

To be clear the loop is just an example. You need to basically subscribe or listen to some kind of event, which then triggers your SSE. You can accomplish this with a couple different ways using observables or event emitters

@@mariusespejo that is, if i run the this.sendEvent(anyData) function from the neighboring endpoint, all clients will receive the message?

The point is not to directly call this.sendEvent, but that sendEvent itself should be subscribed to something, and it will automatically broadcast to clients when what it is subscribed to gets a new event

Couple examples here using an observable stream that you can add events to, or using event emitter stackoverflow.com/questions/67202527/can-we-use-server-sent-events-in-nestjs-without-using-interval

@@mariusespejo this is actually a very complex topic and the simple looping example never covers the topic

Totally! As long as the 6 tab limitation isn’t a problem for you

@@mariusespejo thank you, you are the best

You’ll need to add some kind of event emitter and make your sse method be subscribed to those login events. You might get some ideas here: docs.nestjs.com/techniques/events

@@mariusespejo thanks brother, I will check it out and testing it 🫡

ok it seems the @sse decorator is taking care of that when returning an observable...

Hi Milena! Thanks for checking in, all is good just been busy. Will be posting more soon 🙂

The consumings side should be the same, it’s the same api for client. The server/publishing side I’m not sure for nuxt specifically, I suggest looking at docs

I mean pretty much if you take what I did here, and added something on the client side which pops up a notification… that’s pretty much it

@@mariusespejo I am trying but I am facing some issues with observables, i guess I need to brush up observables concept a little bit

Good topic idea, I’ll see if I can cover it at another time, thanks!

Well this is a standard API not an ASP.NET library like SignalR. Every solution has tradeoffs, even websockets

@@mariusespejo Agreed, can we use SSE to handle graphql subscriptions , any thoughts on that?

Traditionally most graphql implementations, e.g. apollo, have used websockets to implement subscriptions. Wundergraph wrote about using SSE instead but I don’t know much about it yet wundergraph.com/blog/deprecate_graphql_subscriptions_over_websockets

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