I want to create a web app using React as the front end technology. A requirement for the app is that the server will be able to update all the clients with information about changes (not have to be an exact real time, but should update after no more than 10 seconds).
Solutions like clients requesting updates from the server every several seconds are out of the question.
Requirements:
1) The server's should be implemented with either .NET or with Node.js.
2) The connection MUST be secured via port 443 of the IIS.
I read a bit about Micorsoft's SignalR and about Pusher Channels which seems to provide exactly the kind of service I require.
Could you please elaborate about what exactly are the differences between them? When should I choose each? Which of them got more community support? Which is easier to implement? Stuff like that...
Both SignalR and Pusher Channels ultimately both use websockets to deliver messages to clients, so both should meet your requirements to deliver messages to clients in realtime.
1) Both offerings also meet your requirements for both library support:
SignalR supports .NET:
https://dotnet.microsoft.com/apps/aspnet/signalr
Pusher Channels has server support for both nodejs and .NET:
https://github.com/pusher/pusher-http-node
https://github.com/pusher/pusher-http-dotnet
2) Both offerings also meet your requirements for sending messages over TLS/WSS:
SignalR:
https://kimsereyblog.blogspot.com/2018/07/signalr-with-asp-net-core.html
Pusher Channels:
Securing Pusher's messages
In terms of the differences between them this depends on your implementation, if you just run SignalR on your own ISS server then it will be down to you to manage all of the websocket connections and all of the scaling challenges that come with this.
However similar to how Channels works, SignalR also has a managed websocket service, so you do not need to manage the connections or scaling. You just make an API request with the message you want to send to either Channels or SignalR and this message is then broadcast to the interested clients connected by websockets. In this scenario you do not manage the websocket connections yourself.
However in terms of pricing Channels appears to be far more competitive (especially the free offering), so if you are looking at the managed offering Channels looks to be a better value proposition:
https://azure.microsoft.com/en-gb/pricing/details/signalr-service/
https://pusher.com/channels/pricing
Both offerings look fairly similar in terms of implementation (assuming you are using the managed service). The complexity would increase if you implement SignalR on ISS:
https://learn.microsoft.com/en-us/aspnet/core/signalr/scale?view=aspnetcore-2.2
In terms of support Pusher has a free application support offering:
https://support.pusher.com/hc/en-us
Hope this helps!
This presentation has some answers A 10 Minute Guide to Choosing a Realtime Framework
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I have to connect an old but critical software to RabbitMQ. The software doesn't support AMQP, but it can do HTTP Requests.
Does RabbitMQ support plain HTTP? Or should I use a "proxy" or "app" that actively transforms the HTTP Requests to AMQP 1.0 and pushes it to the RabbitMQ server?
https://www.rabbitmq.com/management.html
The management plugin supports a simple HTTP API to send and receive messages. This is primarily intended for diagnostic purposes but can be used for low volume messaging without reliable delivery.
As mentioned, it's designed for very low loads, but it may be usable. If you need higher loads, then by all means cast around for a library that does the job and create a proxy. Most languages will have something. I've personally created a lightweight API using Lumen and https://github.com/bschmitt/laravel-amqp to tie a few disparate services together in the past, and it seems to work very well.
It is possible not but really recommended depending on load. You have three options really, two of which are web socket based and one that seems like what you're looking for. I'd suggest starting with the rabbitmq docs.
As per the KAA references, I understand that once should only use the Notification feature, When it required to send data from server (External apps) to endpoints and Events are only used when there is a need for endpoint to endpoint communication (kind of device binding requirement)
So, To achieve request/response functionality using KAA. I need to implement any hybrid solutions like as below.
1) In my server, I can run one KAA SDK instance and use the event feature for request to the endpoint and response from the endpoint.
OR
2) From my server, I use the notification REST API for request and get the response back through the data logger feature using any in-build appender by configuring "LogUploadStrategy" as to uploads every log record as soon as it is created.
Notes For Point 1
As per Andrew, Solutions Architect of Kaa IoT platform
"You can always embed an SDK to a standalone application and host in
on the same server where kaa-node is present. This application may
receive REST API calls and forward them to particular endpoints via
Kaa events feature. However, this is useful for test purposes. I
would not recommend this solution in production because it is hard to
scale and has potential security issues"
Notes For Point 2
It satisfies the KAA reference document as well as Andrew's suggestion for request only but how can i achieve the response.
Questions For Point 1
1) What causes to scale the application and what type of security issues it faces even through it uses RSA 2048 encryption for communication?
2) Can we embed more then one SDK in standalone application and host in on the same server where kaa-node is present.
Questions For Point 2
3) if device sends the notification response along with the telemetry data, can it increase the latency and any other performance issue.
Common Questions
4) Which one is the better approach to achieve request/response functionality?
Any help or suggestion is really appreciated.
1) What causes to scale the application and what type of security issues it faces even though it uses RSA 2048 encryption for communication?
It makes the EP on the server side as a single point of failure and does not allow load balancing.
About security issues, Andrew meant: This application may receive REST API calls and this forces one to provide additional security for this REST API calls and better use your first hybrid solutions using solely event feature.
2) Can we embed more then one SDK in standalone application and host in on the same server where kaa-node is present.
No, you can't use more than one SDK in one application, but you can run a couple of instance on one machine in different directories
in order to prevent collisions of autogenerated security keys and other files.
3) if device sends the notification response along with the telemetry data, can it increase the latency and any other performance issue.
Of course, you will face some delays if start sending very frequently and big portions of data on both sides. If you have a lot of devices that sends in total a big amount of telemetry data, you can increase performance on the server side by start-up KAA in the cluster mode or add new nodes for processing requests.
4) Which one is the better approach to achieve request/response functionality?
The second hybrid solution – data collection and notification features. This doesn't cause any problem with scale and you can easily launch Kaa server in cluster mode.
I am using the SignalR silverlight client and my hubs are hosted in the windows services. Hubs talk to the compact database to return the data.
What i have noticed is, the time taken to return the data is alarmingly high even though the volume of data returned is not significant and also since the hubs server is local, do not see any network latency issues as well.
I want to know, what are the performance improvements/configurations that can be done at the SignalR hub level in order to improve the performance?
eg:
Is there any standard Transport channel that I should use depending on the client type?
Are there any configuration parameters that i should set?
Thanks,
Alpee
As far as I understand, SignalR uses fallback protocols so it would depend on the capabilities of your server and client.
You might want to take a look to this for further abstract
Moreover, there are some performance recommendations (only related to IIS and SignalR together) in the main project wiki
I would recommend you to use Performance Counters (check "Generating Client Load with crank" section) to better diagnose where is your performance issue.
Hope that helps,
Cheers
I am interested in the Pub/Sub paradigm in order to provide a notifications system (ie : like Facebook), especially in a web application which has publishers (in several web applications on the same web server IIS) and one or more subscribers, in charge to display on the web the notifications for the front user.
I found out Redis, it seems to be a great server which provides interesting features : Caching (like Memcached) , Pub/Sub, queue.
Unfortunately, I didn't find any examples in a web context (ASP.NET, with Ajax/jQuery), except WebSockets and NodeJS but I don't want to use those ones (too early). I guess I need a process (subscriber) which receives messages from the publishers but I don't see how to do that in a web application (pub/sub works fine with unit tests).
EDIT : we currently use .NET (ASP.NET Forms) and try out ServiceStack.Redis library (http://www.servicestack.net/)
Actually Redis Pub/Sub handles this scenario quite well, as Redis is an async non-blocking server it can hold many connections cheaply and it scales well.
Salvatore (aka Mr Redis :) describes the O(1) time complexity of Publish and Subscribe operations:
You can consider the work of
subscribing/unsubscribing as a
constant time operation, O(1) for both
subscribing and unsubscribing
(actually PSUBSCRIBE does more work
than this if you are subscribed
already to many patterns with the
same client).
...
About memory, it is similar or smaller
than the one used by a key, so you
should not have problems to subscribe
to millions of channels even in a
small server.
So Redis is more than capable and designed for this scenario, but the problem as Tom pointed out in order to maintain a persistent connection users will need long-running connections (aka http-push / long-poll) and each active user will take its own thread. Holding a thread isn't great for scalability and technologically you would be better off using a non-blocking http server like Manos de Mono or node.js which are both async and non-blocking and can handle this scenario. Note: WebSockets is more efficient for real-time notifications over HTTP, so ideally you would use that if the users browser supports it and fallback to regular HTTP if they don't (or fallback to use Flash for WebSockets on the client).
So it's not the Redis or its Pub/Sub that doesn't scale here, it's the number of concurrent connections that a threaded HTTP server like IIS or Apache that is the limit, with that said you can still support a fair amount of concurrent users with IIS (this post suggests 3000) and since IIS is the bottleneck and not Redis you can easily just add an extra IIS server into the mix and distribute the load.
For this application, I would strongly suggest using SignalR, which is a .Net framework that enables real-time push to connected clients.
Redis publish/subscribe is not designed for this scenario - it requires a persistent connection to redis, which you have if you are writing a worker process but not when you are working with stateless web requests.
A publish/subscribe system that works for end users over http takes a little more work, but not too much - the simplest approach is to use a sorted set for each channel and record the time a user last got notifications. You could also do it with a list recording subscribers for each channel and write to the inbox list of each of those users whenever a notification is added.
With either of those methods a user can retrieve their new notifications very quickly. It will be a form of polling rather than true push notifications, but you aren't really going to get away from that due to the nature of http.
Technically you could use redis pub/sub with long-running http connections, but if every user needs their own thread with active redis and http connections, scalability won't be very good.
I'm developing a multi-player game and I know nothing about how to connect from one client to another via a server. Where do I start? Are there any whizzy open source projects which provide the communication framework into which I can drop my message data or do I have to write a load of complicated multi-threaded sockety code? Does the picture change at all if teh clients are running on phones?
I am language agnostic, although ideally I would have a Flash or Qt front end and a Java server, but that may be being a bit greedy.
I have spent a few hours googling, but the whole topic is new to me and I'm a bit lost. I'd appreciate help of any kind - including how to tag this question.
If latency isn't a huge issue, you could just implement a few web services to do message passing. This would not be a slow as you might think, and is easy to implement across languages. The downside is the client has to poll the server to get updates. so you could be looking at a few hundred ms to get from one client to another.
You can also use the built in flex messaging interface. There are provisions there to allow client to client interactions.
Typically game engines send UDP packets because of latency. The fact is that TCP is just not fast enough and reliability is less of a concern than speed is.
Web services would compound the latency issues inherent in TCP due to additional overhead. Further, they would eat up memory depending on number of expected players. Finally, they have a large amount of payload overhead that you just don't need (xml anyone?).
There are several ways to go about this. One way is centralized messaging (client/server). This means that you would have a java server listening for udp packets from the clients. It would then rebroadcast them to any of the relevant users.
A second way is decentralized (peer to peer). A client registers with the server to state what game / world it's in. From that it gets a list of other clients in that world. The server maintains that list and notifies the other clients of people who join / drop out.
From that point forward clients broadcast udp packets directly to the other users.
If you look for communication framework with high performance try look at ACE C++ framework (it has Java bindings).
Official web-site is: http://www.cs.wustl.edu/~schmidt/ACE-overview.html
You could also look into Flash Media Interactive Server, or if you want a Java implementation, Wowsa or Red5. Those use AMF and provide native functionality for ShareObjects including synching of the ShareObjects among connected clients.
Those aren't peer to peer though (yet, it's coming soon I hear). They use centralized messaging managed by the server.
Good luck