We are currently implementing a simple chat app that allows users to create conversations and exchange messages.
Our basic setup involves AngularJS on the front-end and SignalR hub on the back end. It works like this:
Client app opens a Websockets connection to our real-time service (based on SignalR) and subscribes to chat updates
User starts sending messages. For each new message, client app calls HTTP API to send it
The API stores the message in the database and notifies our real-time service that there is a new message
Real-time service pushes the message via Websockets to subscribed Clients
However, we noticed that opening up so many HTTP connections for each new message may not be a good idea, so we were wondering if Websockets should be used to both send and receive messages?
The new setup would look like this:
Client app opens a Websockets connection with real-time service
User starts sending messages. Client app pushes the messages to real-time service using Websockets
Real-time service picks up the message, notifies our persistence service it needs to be stored, then delivers the message to other subscribed Clients
Persistence service stores the message
Which of these options is more typical when setting up an efficient and performant chat system? Thanks!
You don't need a different http or Web API to persist message. Persist it in the hub method that is broadcasting the message. You can use async methods in the hub, create async tasks to save the message.
Using a different persistence API then calling signalr to broadcase isn't efficient, and why dublicate all the efforts?
Related
I need to add support for instant messages or reminders to my web application. I was reading that this could be accomplished with websockets.
The idea is that during the time the web app is been used, it could receive messages originated (not as a request response) from the server. For example, the server application might want to remind the user about and unpaid service.
As I understand, when the web app starts it connects to the websocket server through a standard HTTP Request call to announce itself as a client. My question is:
"If I have hundreds of clients connected at the same time, how do I call one in particular?"
Do I need to store every websocket object in an array or something so I can use it to send a message when it is required?
What would be the right approach?
Thanks.
I am looking at developing a client - server application whereby the client will send a message to the server via our API performing an action. The web api (.NET) will hand off this message to a processing queue (Amazon queue at this stage) which will perform operations on it. I would then like to send a message back to the client to indicate that the message has been processed etc.
The only way I can think of to do this is to have the processing queue which is not part of the web api send a HttpPost or HttpPut to the same API my SignalR hub is defined which will send send the messages out to the various clients.
However performance is an issue of this application so I'm hesitant to do another Http call from the backend server to the API just to then get a message sent. Is there any other way I could look at getting these messages sent?
Currently I'm building an application in a micro service architecture.
The first application is an API that does the user authentication, receive requests to initiate/keep a realtime connection with the user (via Socket.io or SockJS) and the system store the socket id into the User object.
The second application is a WORKER doing some stuff and sometime he has to send realtime data to the user.
The question is: How should the second application (the WORKER) send realtime data to the user?
Should the WORKER send a message to the API then the API forward this message to the user?
Or the WORKER can directly send the message to the user?
Thank you
In a perfect world example, the service that are responsible to send "publish" a real time push notifications should be separated from other services. Since the micro service is a set of narrowly related methods, and there is no relation between the authentication "user" service, and the realtime push notification service. And to a deep break down, the authentication actually is a separate service, this only FYI, There might be a reason you did this way.
How the service would communicate? There is actually many ways how to implement the internal communication between the services, MQ solution, which could add more technology to your stack, like Rabbit MQ, Beanstalk, Gearman, etc...
And also you can do the communication on top of HTTP protocal, but you need to consider that the HTTP call will add more cost.
The perfect solution is that each service will have to interfaces to execute on their behalf, HTTP interface and an MQ interface (console)
Pusher service works as illustrated here:
Does it make sense to use it in reverse direction (and switched data channels)? My use case is as follows:
end users (actually mobile, not browser) send messages to Pusher via HTTP-based REST API
my firewalled machine is connected to Pusher via WebSockets API, subscribes channel and receives messages in realtime
This way I can work with Sandbox plan (only 1 persistent connection is used) but mobile app must contain Puser app key.
From what I understand, anyone can use this key to register subscribe same message stream via websockets. Is there a reverse mode, where receiving messages requires knowing the secret? Maybe other service would suit better?
A more secure solution would be for the mobile clients to use client events. Client events can only be triggered on private channels where the subscription to the channel has to be authenticated.The authentication requests should got to an HTTP endpoint that you control so that you can validate the subscription request.
You firewalled machine can either then have a WebSocket connection and receive the client events over that connection. Or it could receive the client events via client event WebHooks if it exposes an HTTP endpoint.
I have a Java application which I make available via RESTful web services. I want to create a mechanism so clients can register for notifications of events. The rub is that there is no guarantee that the client programs will be Java programs and hence I won't be able to use JMS for this (i.e. if every client was a Java app then we could allow the clients to subscribe to a JMS topic and listen there for notification messages).
The use case is roughly as follows:
A client registers itself with my server application, via a RESTful web service call, indicating that it is interested in getting a notification message anytime a specific object is updated.
When the object of interest is updated then my server application needs to put out a notification to all clients who are interested in being notified of this event.
As I mentioned above I know how I would do this if all clients were Java apps -- set up a topic that clients can listen to for notification messages. However I can't use that approach since it's likely that many clients will not be able to listen to a JMS topic for notification messages.
Can anyone here enlighten me as to how this problem is typically solved? What mechanism can I provide using a RESTful API?
I can think of four approaches:
A Twitter approach: You register the Client and then it calls back periodically with a GET to retrieve any notifications.
The Client describes how it wants to receive the notification when it makes the registration request. That way you could allow JMS for those that can handle it and fall back to email or similar for those that can't.
Take a URL during the registration request and POST back to each Client individually when you have a notification. Hardly Pub/Sub but the effect would be similar. Of course you'd be assuming that the Client was listening for these notifications and had implemented their Client according to your specs.
Buy IBM WebSphere MQ (MQSeries). Best IBM product ever. Not REST but it's great at multi-platform integration like this.
We have this problem and need low-latency asynchronous updates to relatively few listeners. Our two alternative solutions have been:
Polling: Hammer the list of resources you need with GET requests
Streaming event updates: Provide a monitor resource. The server keeps the connection open. As events occur, the server transmits a stream of event descriptions using multipart content-type or chunked transfer-encoding.
In the response to the RESTful request, you could supply an individualized RESTful URL that the client can monitor for updates.
That is, you have one URL (/Signup.htm, say), that accepts the client's information (id if appropriate, id of object to monitor) and returns a customized url (/Monitor/XYZPDQ), where XYZPDQ is a UUID created for that particular client. The client can poll that customized URL at some interval, and it will receive a notification if the update occurs.
If you don't care about who the client is (and don't want to create so many UUIDs) you could just have separate RESTful URLs for each object that might want to be monitored, and the "signup" URL would just return the correct one.
As John Saunders says, you can't really do a more straightforward publish/subscribe via HTTP.
If polling is not acceptable I would consider using web-sockets (e.g. see here). Though to be honest I like the idea suggested by user189423 of multipart content-type or chunked transfer-encoding as well.