We are building an app which will send messages to the browser using SignalR. The user may have multiple browser instances open and we would like each message to be sent to the appropriate browser. Our understanding is that the ClientId ConnectionId would allow us to do this. The issue we're running into is accessing the ClientId ConnectionId, or SessionId, at the appropriate times in the codebase. Here's our scenario:
A MVC Action executes and, as part of that processing, a call to a Biztalk endpoint is made. The Biztalk execution is out of process (from the point of view of the MVC Action) and doesn't return when completed. This is by design. To notify the MVC application that it has completed, Biztalk sends a message to the MVC application's SignalR hub by calling the /myapp/signalr endpoint. The message is received by SignalR and then should be routed to the appropriate browser instance.
Since the message to SignalR is being sent by Biztalk, and not the MVC application, the ClientId of the connection to SignalR is not the one that identifies the browser instance that should receive the message. So what we are attempting to implement is somethign similar to the Return Address pattern by including the ClientId ConnectionId of the browser instance that initiates the Biztalk call in the message to Biztalk. When Biztalk sends its message to SignalR one of the contents is that original ClientId ConnectionId value. When SignalR processes the message from Biztalk it then can use the ClientId ConnectionId included in the message to route that message to the appropriate browser instance. (Yes we know that this won't work if the browser has been closed and re-opened and we're fine with that.)
The problem we face is that when initially sending the message to Biztalk from our MVC Action we cannot access the ClientId ConnectionId as it's only available in the Hub's Context. This is understandable since the MVC Action doesn't know which Hub context to look for.
What we have tried in it's place is to pass the SessionId through the Biztalk message and return it to SignalR. This solves the problem of including the browser instance identifier in the Biztalk message and returning it to SignalR. What it introduces is the fact that when a client connects to the Hub we cannot access the Session (and thus the SessionId) in the Hub's OnConnect method.
David Fowler posted a gist that reportedly shows how to make readonly SessionState accessible in a Hub but it doesn't work. (https://gist.github.com/davidfowl/4692934) As soon as we add this code into our application messages sent to SignalR cause a HTTP 500 error which is caused by SignalR throwing the following exception.
[ArgumentNullException: Value cannot be null.Parameter name: s]
System.IO.StringReader..ctor(String s) +10688601
Microsoft.AspNet.SignalR.Json.JsonNetSerializer.Parse(String json, Type targetType) +77
Microsoft.AspNet.SignalR.Json.JsonSerializerExtensions.Parse(IJsonSerializer serializer, String json) +184
Microsoft.AspNet.SignalR.Hubs.HubRequestParser.Parse(String data) +101
Microsoft.AspNet.SignalR.Hubs.HubDispatcher.OnReceived(IRequest request, String connectionId, String data) +143
Microsoft.AspNet.SignalR.<>c__DisplayClassc.<ProcessRequest>b__7() +96
Microsoft.AspNet.SignalR.<>c__DisplayClass3c.<FromMethod>b__3b() +41
Microsoft.AspNet.SignalR.TaskAsyncHelper.FromMethod(Func`1 func) +67
No matter the mode that we set SessionStateBehavior (as shown by David Fowler's gist) we either get this exception when sending a message to the Hub or SessionState is null when we are in the Hub's OnConnect.
So, after all that pre-amble, what we are asking is how do people update the appropriate client when working with this type of disconnected messaging in SignalR?
If you're looking to send data to clients outside of a normal request to a hub then I'd recommend having a static Concurrent Dictionary on your hub that manages your users and maps them to corresponding connection Id's.
With this approach you can send to any user at any point based on their mapped Connection Id. Therefore when sending your data to Biztalk all you need to do is send your user id (created by you) and then when the data flows back to SignalR you can lookup the ConnectionId (if one exists) for that given user id.
Lastly, you can manage your user mappings by adding users to your concurrent dictionary in OnConnected, adding only if they are not there in OnReconnected, and removing in OnDisconnected.
Related
I have a .Net Core 2.1 Web API talking to a MySQL database, using the Pomelo provider (version 2.1.0-rc1-final). Because this is a multi-tenant application, the API needs to change databases depending on which tenant is connecting. The front end web app tells the API which tenant is doing the request by including a TenantId header in the HTPP request.
When the API receives an HTTP request from the front end, I have a service in the API's pipeline that reads the TenantId from the request, and then this is used to determine which database the API must connect to.
To connect to various databases, I change the connection string of the DbContext. I do this in the OnConfiguring event:
protected override void OnConfiguring(DbContextOptionsBuilder options)
{
string connectionString = CreateConnectionString();
optionsBuilder.UseMySql(connectionString);
base.OnConfiguring(optionsBuilder);
}
My problem is that this works the first time, but the second time this event fires, when it executes the optionsBuilder.UseMySql(connectionString); line, it throws this exception:
An item with the same key has already been added. Key: Pomelo.EntityFrameworkCore.MySql.Infrastructure.Internal.MySqlOptionsExtension
It's only letting me configure the DbContext once. I need to reconfigure it every time an API action endpoint gets called. Any ideas?
I'm not 100% sure what I did - but it's working now. The process is as follows: I created middleware to identify the tenant making the request (i.e. consuming the API). This is done by reading a "tenantId" that the client app sends in the header of the request, and then saving that tenantId into a global variable (I used HttpContext). Because middleware executes before pretty much most other things, by the time the OnConfiguring event of the dbContext fires, I already know which tenant this is So then, on the OnConfiguring event of the dbContext, I set the connectionString of the dbContext to whatever it should be (depending on the tenantId). I can't post the code in this comment because comments don't allow line breaks and they are too short, but If you want to, send me your email address and I'll email you the code.
I have a web application which has few charts on dashboard. The data for charts is fetched on document.ready function at client side invoking a WCF service method.
What i want is now to use SignalR in my application. I am really new to SignalR. How can i call WCF methods from SignalR Hub or what you can say is that instead of pulling data from server i want the WCF service to push data to client every one minute.
Is there a way of communication between signalR and WCF service.
Also another approach can be to force client to ask for data from WCF Service every minute.
Any help will be really appreciated.
I have done following as of yet.
Client Side Function on my Dashboard page
<script src="Scripts/jquery.signalR-2.0.3.min.js"></script>
<!--Reference the autogenerated SignalR hub script. -->
<script src="/signalr/hubs"></script>
<a id="refresh">Refresh</a>
$(function() {
var dashboardHubProxy = $.connection.dashboardHub;
$.connection.hub.start().done(function() {
// dashboardHubProxy.server.refreshClient(parameters);
$("#refresh").click(function() {
dashboardHubProxy.server.refreshClient(parameters);
});
});
dashboardHubProxy.client.refreshChart = function (chartData) {
debugger;
DrawChart(chartData, 'Hourly Call Count For Last ' + Duration + ' Days', '#chartHourly', 'StackedAreaChart');
};
});
and my Dashboard Hub class is as follows
public class DashboardHub : Hub
{
private readonly ReportService ReportService = new ReportService();
public void RefreshClient(string parameters)
{
var chartData = ReportService.GenerateHourlyCallsTrendGraphicalReport(parameters);
Clients.All.refreshChart(chartData);
}
}
My SignalR startup class is as follows
[assembly: OwinStartup(typeof(CallsPortalWeb.Startup), "Configuration")]
namespace CallsPortalWeb
{
public static class Startup
{
public static void Configuration(IAppBuilder app)
{
ConfigureSignalR(app);
}
public static void ConfigureSignalR(IAppBuilder app)
{
app.MapSignalR();
}
}
}
When i click on refresh button and a debugger on RefreshClient method on hub the debugger doesn't get to the method which means i am unable to call server side method of SignalR.
Is there anything needs to be done in web.config?
I agree with AD.Net's comment. To elaborate slightly more though, the SignalR hubs can be hosted directly in your web project kinda the same way controllers are used. There is also a package out there so you can host the SignalR library on its own so it can act as a service all on its own. Either way you will need to hit the SignalR hub first as that is how it communicates then you would call your WCF service methods from within the hubs.
Brief explanation
Your HUB will have methods used by both your USER Client and your WCF Client. You may use something like UserConnected() for the user to call in and setup your logging of the connection. Then the WCF service may call your HUB with an UpdateUserStats(Guid connnectionId, UserStats stats) which would in turn call the USER client directly and provide the stats passed in like so Clients.Client(connectionId).updateStats(stats) which in turn would have a method on the USERS client named updateStats() that would handle the received information.
Initial page landing
What AD.Net provided is basic code that will be called when the user lands on the page. At this point you would want to log the ConnectionId related to that user so you can directly contact them back.
First contact with your hub touching WCF
From your Hub, you could call your WCF service as you normally would inside any normal C# code to fetch your data or perform action and return it to your user.
Method of updating the user periodically
SignalR removes the need for your client code to have to continually poll the server for updates. It is meant to allow you to push data out to the client with out them asking for it directly. This is where the persistence of the connections come into play.
You will probably want to create a wrapper to easily send messages to the hub from your application, since you are using WCF I would assume you have your business logic behind this layer so you will want the WCF service reaching out to your Hub whenever action X happens. You can do that by utilizing the Client side C# code as in this case your client is actually the user and the WCF service. With a chat application the other user is basically doing what you want your WCF service to do, which is send a message to the other client.
Usage example
You are running an online store. The dashboard displays how many orders there have been for the day. So you would wire up a call to the hub to send a message out to update the products ordered when a user places a new order. You can do this by sending it to the admin group you have configured and any admins on the dashboard would get the message. Though if these stats are very user specific, you will more then likely instead reach into the database, find the ConnectionId that the user has connected with and send the update message directly to that connectionid.
WCF Client Code Example
Just incase you want some code, this is directly from MS site on connecting with a .net client. You would use this in your WCF service, or wherever in your code you plan on connecting and then sending an update to your user.
var hubConnection = new HubConnection("http://www.contoso.com/");
IHubProxy stockTickerHubProxy = hubConnection.CreateHubProxy("StockTickerHub");
stockTickerHubProxy.On<Stock>("UpdateStockPrice", stock => Console.WriteLine("Stock update for {0} new price {1}", stock.Symbol, stock.Price));
await hubConnection.Start();
Here is a link directly to the .Net Client section: http://www.asp.net/signalr/overview/signalr-20/hubs-api/hubs-api-guide-net-client
I am sure you have seen this link but it really holds all the good information you need to get started. http://www.asp.net/signalr
Here is a more direct link that goes into usages with code for you. http://www.asp.net/signalr/overview/signalr-20/hubs-api/hubs-api-guide-server
ADDED: Here is a blog specific to Dashboards with SignalR and their polling.
http://solomon-t.blogspot.com/2012/12/signalr-and-interval-polling-for.html
ADDED: Here is a page on managing users signalR connections.
http://www.asp.net/signalr/overview/signalr-20/hubs-api/mapping-users-to-connections
Update for your code update
The .Net Client library (in NuGet) gives your .net code access to the hub. Since you are a client you will need to connect to the hub just like the User who is also a client. Your hub would act as the server for this. So with the .Net Client I am assuming you would setup a windows service that would internally poll, or something event based that would call the .Net Client code portion of it which would reach out to your hub. Your hub would take the information provided, more than likely a ConnectionId or GroupId and broad cast the User (which is perhaps on a website so it would be the JS client) a method that would update the front end for the user client. Basically what I mention under "Brief Explanation".
Now, to directly respond to the code you posted. That is Javascript, I would expect a connect like you have done. Updating the chart on initial connection is fine as well. If this is all the code signalR wise though you are missing a client side method to handle the refresh. Technically, instead of calling Clients.Caller.RefreshChart() you could just return that data and use it, which is what your javascript is doing right now. You are returning void but it is expecting a your date.
Now, I would actually say correct your javascript instead of correcting the hub code. Why? Because having a method in JS on your client that is called "refreshChart()" can be reused for when you are having your server reach out and update the client.
So I would recommend, dropping anything that is related to updating the dashboard in your JS done statement. If you want to do a notification or something to the user that is fine but dont update the grid.
Now create a JS client function called "refreshChart", note the lower case R, you can call it with a big R in c# but the js library will lowercase it so when you make the function have it will receive your dashboard information.
Now, on the server polling, or executing on some action, your WCF would call a method on the hub that would be say "UpdateDashboar(connectionId,dashInfo)" and that method would then inside of it call the "refreshChart" just like you are doing in your RefreshClient method, accept instead of doing Clients.Caller you would use Clients.Client(connectionId).refreshChart(chartInfo).
Directly the reason your code is not working is because you need to turn that Void into the type you expect to be returned. If the rest is coded right you will have it update once. You will need to implement the other logic I mentioned if you want it constantly updating. Which is again why I asked about how you are persisting your connections. I added a link to help you with that if you are not sure what I am talking about.
You should use the SignalR Hub to push data to the client. Your hub can consume a WCF service (the same way your client can) to get the data.
from client:
hub.VisitingDashBoard();
on the hub in the VisitingDashBoard method:
var data = wcfClient.GetDashboardData()//may be pass the user id from the context
Clients.Caller.UpdateDashboard(data)
Of course your client will have a handler for UpdateDashboard call
I have two classes, client and user. User is a field in client (there is a foreign key). I am trying to do a join, getting all the clients and the related user (it is one to one).
I am using Entity Framework and a web service that gives me my data.
I currently am getting all my clients like:
public DbSet<Client> getClients()
{
return context.Clients;
}
I need to also get the related object user. I found an example that tells me to do:
public DbSet<Client> getClients()
{
return context.Clients.include(x => x.User);
}
This throws an exception, I need to be working with IQueryable. If I change my function the connection to the web service does not work.
How do I do what I am trying to do?
EDIT:
The exception I get from the webservice is An error occurred while receiving the HTTP response to http://localhost:60148/WebService.svc. This could be due to the service endpoint binding not using the HTTP protocol. This could also be due to an HTTP request context being aborted by the server (possibly due to the service shutting down). See server logs for more details.
try these links:
Expose IQueryable Over WCF Service
and IQueryable problems using WCF you need to send something else back, like a List, as IQueryable is actually a query, which you can't send back. the links above provide alternative ways to do it, to get around the IQueryable restriction.
I recently started using Signal R library in ASP.Net MVC 3 application. I am able to use Signal R to send message to client. But I noticed that if I logged in to the application from another browser, I get following error -
Exception type: InvalidOperationException
Exception message: Unrecognized user identity. The user identity cannot change during an active SignalR connection.
Server stack trace:
at Microsoft.AspNet.SignalR.PersistentConnection.GetConnectionId(HostContext context, String connectionToken)
at Microsoft.AspNet.SignalR.PersistentConnection.ProcessRequest(HostContext context)
at Microsoft.AspNet.SignalR.Owin.CallHandler.Invoke(IDictionary2 environment)
at Microsoft.AspNet.SignalR.Owin.Handlers.HubDispatcherHandler.Invoke(IDictionary2 environment)
at Microsoft.Owin.Host.SystemWeb.OwinCallContext.Execute()
at Microsoft.Owin.Host.SystemWeb.OwinHttpHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object extraData)
And in some instances, I started getting this error repeatedly. And event log get full in couple of minutes.
I override OnConnect, OnDisconnect functions in my hub class and initiated hub connection from the Java script.
SignalR does not allow a user's Identity to change while maintaining a connection. This is because SignalR's connectionToken acts as an anti-xsrf token.
It appears that your "other" browser must actually be just another browser window. When you log in to the application in another window, it changes your ASP.NET forms authentication cookie (and therefore your Identity) in both browser windows.
Any ongoing SignalR connections will run into the aforementioned InvalidOperationException when they attempt to reconnect after the browser's auth cookie has changed. SignalR may attempt to reconnect quite frequently if the long polling transport is being used. Once the reconnect fails due to the exception, SignalR will repeatedly try to reconnect for about 40 seconds after which SignalR will give up and disconnect.
I am creating a WCF (with callbacks) service currently hosted as a process but will be a service eventually.
I am using netTCP binding in a Windows Domain environment and the client is on another machine within the domain (windows forms client).
I have all the binding, methods etc working with Windows security at transport level and an SPN in place.
I am now implementing security and am attempting to use this pattern on some methods (not all need to be secured):
<PrincipalPermission(SecurityAction.Demand, Role="MyDomain\DataReader")>
public Function GetData() As String
return "Test String"
End Function
(example)
This correctly allows users and blocks those not in role.
My problem is that an exception is raised at the service end (I can see this in VS as the process is run from there). The client does not get an security exception but times out instead.
How do I correctly pass back to the caller that a security exception occurred so that the I can then pass a message to the user.