I have an MVC website sitting onto of some fairly hefty business objects. My MVC Controllers call Manager objects which conducts and delegates work off to other sets of objects.
Basically the code is deep server side, while a Hub in a way is just like a Controller in that it is fairly close to the client side.
Is there a way to execute SignalR methods based on a reference to the Hub passed to these Manager objects?
If your MVC and SignalR services are running on the same process, you can call GlobalHost.ConnectionManager.GetHubContext("MyHub");
It they are on separate processes, then you need to create a SignalR client in your MVC app
Well all of the clients will connect to your web app and persist the connections there. From a separate back end program you can just call a web service in your web app and that web service can post the message on the same SignalR hub in your web project. Your back end app can't connect to the SignalR hub directly. It all flows through a single point, being your web app.
If you are just talking about a shared class library in the same web app, you should be able to pass the hub object to the other class as the other person answered: GlobalHost.ConnectionManager.GetHubContext("MyHub");
Related
I have an ASP.NET Owin Web Api which is load balanced, which means there are multiple instances of it which don´t know each other. The web api hosts a SignalR hub with an SQL Server Backplane (for synchronising between instances), so clients can exchange messages regardless of which instance of the web api they are connected to. Everything working so far.
Client session data is stored in the db. The web api needs this info for processing requests for the client. Because it would be too slow to read the session data from the db for every client request, the web api is reading it only once (on first request from the client session) and caching it in-memory. This also works across multiple instances of the web api as every instance is holding it´s own session data cache.
But now the clients should be allowed to change for example the language, which results in an updated language in the session data stored in the db. The web api instance which processes the "change-language"-request of course can react to the changed session data and clear the session from it´s cache, which will lead to a reread of the session data from the db on the next client request. But the other web api instances don´t know about the session data change, their caches now hold outdated session data.
The web api instance which processes the "change-language"-request would somehow need to notify the other instances to drop their cache for session xyz. Unfortunately the instances don´t know each other, but all instances host SignalR hubs which are synchronised through the SingalR SQL server backplane.
Unfortunately a SignalR hub cannot directly send and receive messages. A HubConnection (client) is needed to do that. So the idea is when every web api instance is connecting to it´s own SignalR hub, it would be able to send messages to itself, which are then spread out to the other instances via the SQL server backplane synchronisation. But a HubConnection can only be established with an URL (http://host:port/signalr) but the web api instance doesn´t know it´s own base url.
So finally my question is:
Is there any way to establish a HubConnection to a hub running in the same process without providing an URL (I have access to the hub object)?
If not, is there any way for a SignalR hub to spread out messages and listen to messages through the backplane without a client (hub-2-hub communication)?
If not what else could I do to notify other instances of my load balanced web api and advice them to drop their session data cache?
Solved through distributed caching (IDistributedCache), as mentioned by Panagiotis Kanavos in the comments.
Using SignalR, is it possible to update website clients from my WCF service if the service is not used by these clients directly?
I have a desktop application in .NET which has WCF service used internally using net.TCP protocol. This application changes one of the status fields in database table depending on certain user actions. I want to notify this change to end users who are accessing a different website hosted on the same web server.
I have tried one SignalR sample where notification works fine if it is sent from same website's host to its own client (stock ticker sample). But in my case, the message should go from WCF service to a website client.
IMO you should do an intermediate hop, for example having your website exposing an endpoint (you pick the technology) where you can post whenever you have a change to notify. Your WCF service would post there whenever there's a change, and the web app would process the post by broadcasting info to the target clients (can be all, or can be just some you filter with some logic behind the post). I use this pattern quite frequently, implementing it with HTTP POST. You would have no issues to implement the SignalR infrastructure in the web app, which is where your clients already connect to.
I have a WCF service hosted at IIS7 web application. It's created by a WebServiceHostFactory. The client connects to a service calls the Collect method, and data are stored to DB. All working fine.
Now I would like to refresh page every time the new data are "collected" (i.e. the service method Collect is called).
My question is: What is the best approach ?
I was considering the CallbackContract, but this would require a singleton pattern (service is now PerCall), or is it a wrong assumption ? Is this approach possible ?
My logic is:
ASP.NET page subscribes to WCF service
the service singleton is created from now on
when method is called the services calls subscribers (clients)
there should be therefore only one service instance in order to subscription to work (or is it ?)
the client page refreshes itself
regards,
Kate
You can't refresh the page in a user's browser from the sever. Browsers use HTTP, which is a request-response protocol, so if the browser hasn't issued a request, it won't be looking for a response from your server.
If you have a Silverlight application hosted in a browser, that's a different story, but you didn't mention Silverlight anywhere. You would also be able to do what you're asking using WebSockets in HTML5, but that's not fully standardized yet.
Can I make an asynchronous call from one web service to another web service deployed on different server?
The scenario is that an ASP.NET webforms page will call a web service in an async manner. This particular web service will then make another async call to a second web service deployed on different web server.
This this possible to achieve, and what additional steps or code would be necessary to make this happen?
It shouldn't be any more difficult than just calling the initial web service in the first place. Website A has a reference to WebService B and makes a call to that service (in response to some kind of action on Website A). WebService B has a reference to WebService C and makes a call to that service (in response to the action being invoked by Website A). Website A shouldn't know/care anything about WebService C, and vice/versa.
Or do A and C actually need to know about each other in your scenario? If so, that changes things.
I have an ASP.NET application that calls other web services through SSL (outside the application). I simply added a web reference (https://url/some.asmx) and used the web services and it works well. However, my questions are, how is the connection (channel) managed? is the connection to web services dropped after each web services call? or do they use the same connection (channel) for the subsequent calls? if they do, how long is the trusted connection kept alive?
Classic ASMX web services maintain the connection for a single request - that's why the methods you call via the web service class must be static. A SOAP call is very similar to a plain vanilla HTTP Request:
Open connection to URL
Pass in request - get/post, etc
Server renders an XML (SOAP) response
Connection is closed
Client processes response.
The web service framework wraps most of this so that you can conveniently access the web service as if it were a local object, but there is no server-side object instance persistence any more than there is for an ASPX page.
WCF services, on the other hand, maintain the connection until the proxy object is closed. This gives you a LOT of power, but, of course, with great power comes great responsibility.
update: link regarding ssl caching:
http://social.msdn.microsoft.com/forums/en-US/asmxandxml/thread/f86066e0-a24b-4d5e-873c-ed427d1faef7/