I'm currently hosting 2 webstites (clientportal and admin), in windows azure websites.
I'm going to introduce SignalR right now, to get rid of javascript polling. What I need, is when an admin send a broadcast message on the admin site, all the active client should be receive it. Now, the clien polls the webserver all the time, when an ajax poll receives, the webserver check for new messages in the database.
What would be the best way, to notify the client webserver from the admin webserver? WebApi is ok for this? Or are there any simple way?
From the point of view of Azure Websites and SignalR, it is transparent who is the Client and who is the Admin. This is an implementation detail, and thus, there are many ways to do it.
SignalR is split in two parts: The javascript library, and the .NET library that you use to create your "Hub". One way to accomplish what you are trying to do is to implement the Hub functionality in your Admin back-end using the .NET side of SignalR and ASP.NET Web API; and use the javascript side of SignalR to subscribe and listen for notifications on the Client side.
Another way to do it is to create a third component, just for the SignalR Hub, independent of both the Client and the Admin websites. In this scenario both the Admin and the Client would subscribe to the Hub, but only the Admin would push, and the Client would listen.
You can find many working examples on the internet. This is one of them: http://msdn.microsoft.com/en-us/magazine/hh965663.aspx
I hope this answers your questions.
Related
We're planning on adding SignalR to several differnet web applications. The applications are targeted different aspects of an order. When something happens to an order, all users working with the order across all web applications should be notitfied.
Changes to an order are availible asa message on a servicebus.
We could implement the following logic in all web applications:
Subscribe to a topic (one subscription per webapp)
OnMessage -> Send orderId to hub
Hub would notify clients working on the orderId
Question is: Could we implement all this common functionality in a separate application, and all web apps would reference the same signalr scripts?
All applications live on the same domain, and it would give us a lot of benefit not having to implement signalr in every app.
Good idea, or am I missing something important here?
Edit: Put in other words: I have WebAppA, WebAppB and WebAppC all without SignalR. I'm asking if its possible to create a WebappD that talks to clients in WebApp A,B,C
Second Solution is very good. it will move signalr load (espcially memory) from your main web apps to WebAppD(signalr web app). And all your main web apps will not be dependent to signalr.
Drawbacks: You don't have any authentication on WebAppD. Because clients are authenticated on the other WebApps. You should let the WebAppD knows about orderId. That's why, you should send message to server (WebAppD) from clients(Javascript).
Because of enable cross domain settings, anyone can send message to server. Even they don't need to be connected WebAppA,WebAppB or WebAppC. Even if you solve this problem (virtual path etc), Someone is connected but not authenticated on WebAppA,WebAppB,WebAppC can sends message. Because WebAppD just get the message and it doesn't know this client is authenticated or not so it will serve this message to all others. In Short: Someone can send fake messages to other clients.
So you should share your authentication like this (or some other logic) between your web app and signalr webapp.
Other than this I couldn't see any drawback.
I am trying to find the best solution to build the application at work.
1) My client has a web service, I need to have a automatically process to pull data from client web service, store in a database. The data will be displayed in a aspnet MVC web application. Once new data coming in, I want to notify the current user (something like a badge)
Question 1: I have two ideas for the process to pull data from client's web service,
A)I create a WCF service, and host it as a Windows Service
B)Create a console application and get the schedule task to run the console application
Question 2: I am thinking to use SignalR to indicate users of the new data, but in the backend how do get SignalR to check the data changes?
Thanks very much guys
Regards
Question 1: I have two ideas for the process to pull data from
client's web service, A)I create a WCF service, and host it as a
Windows Service B)Create a console application and get the schedule
task to run the console application
Did you mean WCF client? To pull data from client's web service you need a WCF client not a service? The rest looks ok to me here.
Question 2: I am thinking to use SignalR to indicate users of the new
data, but in the backend how do get SignalR to check the data changes?
SignalR is just a mean to send notifications to clients. The way you check for updates depends on the nature of the notification. So you would better elaborate on this part to get a better advice. A common way to do it is to have a notifications log table/queue which you can check for updates, process them and send to the clients. Don't forget to remove or mark processed notification in the table.
Alternatively, you can host SignalR in a windows service with a WCF client and a timer to pull data from web services. You can notify your web users directly from the windows service. Please see this article Tutorial: SignalR Self-Host
Hope it help!
I have a smart grid system where multiple hardware devices are sending raw sensor data to an Azure Queue. Each device sends a single data packet once every minute. Multiple Worker Roles process the data packets on the queue and push the data to Table Storage. I have a Web Role which holds the application for users to view their device data and a host of other alerts and messages relating to their smart energy system. At the moment the web application just uses ajax polling at one minute intervals to get the latest data updates and any other messages and alerts. Instead of using ajax 'pulling', I'd like to use SignalR instead and 'push' the updates from the cloud when they become available. I'm not sure on what the overall architecture might look like.
So far I have added a SignalR Hub to my Web Role, just to see if I could do that. And it works fine. However, how do I trigger updates from this Hub when there are changes in Table Storage? Should I host the Hub with the Worker Roles that process the raw data, and then make a cross-domain SignalR connection from the web app (client)? Can I even associate an endpoint with a Worker Role? If I have many Worker Roles wouldn't I only be able to connect to one of them, and therefore miss data updates from other Worker Roles?
Perhaps I should create a separate Web Role to host the SignalR hub, but then how do I communicate the changes from the Worker Roles that process the raw data to the hub? Maybe I need to include another Azure Queue that takes messages from the Worker Roles regarding data updates, alerts, and any other messaging, and that queue is processed by the SignalR server. However, would this approach be scalable? If I have multiple instances of the SignalR server processing the message queue(s), would they share the same end point and be aware of all the client connections across the instances? Or maybe the Worker Roles themselves connect as clients to the SignalR server and the messages forwarded from there to the clients.
Is SignalR even the right approach to take if data is being generated at a predictable rate of once every minute for each device. Maybe for updates of this regular data ajax 'pulling' is the best approach, and I should just be using SignalR for the infrequent alerts and messages, although, again, how do I communicate these events from the Worker Roles to the SignalR server?
What overall architecture would suit my needs here?
EDIT 06-09-2014 Half the problem solved
I came across http://www.asp.net/signalr/overview/signalr-20/performance-and-scaling/scaleout-with-windows-azure-service-bus which seems to be exactly what I am after. This deals with the problem of multiple Hub server (Web Role) instances. Now I just need a SignalR client library that can run on the Worker Roles so that they can notify the Hub that new data is available, and the Hub class can then be enhanced to route the new data to the appropriate connected web clients.
EDIT 06-10-2014 A workable solution found
I have added an answer to my question of "What architecture". I thought a quick summary of my setup might be useful. I have many remote devices associated with different users posting real-time data to Azure Queues. The data posted to these queues are parsed and saved to Table Storage, by a number of Worker Roles. Web Roles provide the MVC5 web application for the users (clients) to log on and review their data. I wanted a mechanism by which when new data was posted, any connected clients would receive a real-time notification (and data tables and charts in the client apps could be updated accordingly). SignalR with Service Bus scaleout proved to be the answer.
The first part of the solution I needed was to deploy a SignalR hub that the clients could connect to, to receive any notifications sent. I couldn't use the basic SignalR solution as the MVC5 web app is hosted on a Web Role that will likely have more than one instance - the problem was how to keep all these instances synced so that whatever instance a client was connected to they'd still receive the notifications. SignalR scaleout with Azure Service Bus proved to be the answer to that part of the problem. Details of how to set this up can be found at: http://www.asp.net/signalr/overview/signalr-20/performance-and-scaling/scaleout-with-windows-azure-service-bus - it was VERY easy to setup.
The second part of the problem was how to generate the notifications originating from the Worker Roles (my queue data processors). First I needed to be able to host OWIN in my worker roles - the instructions provided at http://www.asp.net/aspnet/overview/owin-and-katana/host-owin-in-an-azure-worker-role were more than sufficient. Once this was done I created an empty Hub instance with the same name as the one deployed on my Web Roles (it was empty because I didn't expect to have an clients connected to it directly), and changed the Startup class to:
public class Startup
{
public void Configuration(IAppBuilder app)
{
String connectionString = "[Service Bus Connection String]";
GlobalHost.DependencyResolver.UseServiceBus(connectionString, "[App Name]");
app.MapSignalR();
}
}
With this in place if I want to send a notification out to the clients, from the Worker Roles, I do something like:
var context = GlobalHost.ConnectionManager.GetHubContext<MyHub>();
context.Clients.All.clientMethod("[Message]");
What really happens is that a copy of the message gets pushed to the backplane (Service Bus) and is picked up by the Web Roles and pushed out to the connected clients. In reality I will check who is online (in the Web Role Hub instance I override the OnConnected method to save the user's connection id in their profile which is stored in Table Storage), and only create notifications that are associated with those users to reduce SignalR traffic.
Can i have mechinism to have push notification to .NET MVC application once user comes online? Like facebook and gmail? I am going to deploy my app in 3 part.
1) MVC application
2) WCF Service
3) Azure SQL
Everything would in Windows Azure.
Thanks.
If I understand your question correctly, then you might be interested in SignalR. Here is the link http://signalr.net. SignalR allows you to push content from the server to the client. It comes with client side js library and also server side component. SignalR is very easy to implement and provides a very powerful set of abstractions that otherwise would be very difficult to program.
I have an existing complex website built using ASP.NET MVC, including a database backend, data layer, as well as the Web UI layer. Rebuilding this website in another language is not a feasible option.
There are some UI elements on some views (client side) which would benefit from live interactivity, involving both push and pull, so rather than implement some kind of custom long polling or websocket server in asp.net, I am looking to leverage node.js for Windows, and Socket.io.
My problem is that I need two way communication between both applications. Each user should only be able to receive data once they are authorised on the ASP.NET website, so I first need communication for this. Secondly, once certain events occur on the ASP.NET website I want to immediately push this data to the Node server, to be broadcast to specific users or groups of users. Thirdly, I would like any data sent to the node.js server to be pushed to the ASP.NET website for processing, as this is where all our business logic lies. The sole reason for adding Node.js is to have the possibility to push data directly to the client, I do not want to build any business logic into it (or as little as possible).
I would like to know what the fastest method of two-way push communication is between Node.Js and ASP.NET. The only good option I'm aware of so far is to create a special listener on a specific port on the node.js server and connect to that, but I was wondering if there's a more elegant or more efficient method? I also know that you could use a database inbetween but surely this would need to be polled and would be less efficient? Both servers will be running on the same server under a Visual Studio project.
Many thanks for any help you can provide.
I'm not an ASP.NET expert, but I think there are multiple ways you can achieve this:
1) As you said, you could make Node listen on a specific port for data and then react based on the data received (TCP)
2) You can make POST requests to Node.js (HTTP) and also send an auth-key in the process to be extra-secure. Like on 1) Node would react to the data you send.
3) Use something like Redis for pub-sub, send messages from ASP.NET (pub) and get them on the Node.js part (sub). This is even better if you want to scale your app across multiple machines etc.
The only good option I'm aware of so far is to create a special
listener on a specific port on the node.js server and connect to that,
but I was wondering if there's a more elegant or more efficient
method?
You can try to look at redis pub/sub model where ASP.NET MVC application and node.js would communicate through separate channels in order to achieve full-duplex communication. Or you can also try to use CouchDB change nofitications.
I also know that you could use a database inbetween but surely this
would need to be polled and would be less efficient?
Former techniques do not require you to poll for changes, but instead they will notify you when the changes happens or channel message arrives.