I am evaluating SignalR (which happens to be used with Knockoutjs) to see if we can use it to notify clients of concurrency issues. Basically user "a" saves a record and users "b,c,d,e,f,g" are notified. I basically have an example working that notifies all clients. So I think I am almost there.
I came across this link and it lead me on the current path that I am on. I have also been looking at the documentation on Github.
Basically I want to exclude the a single client from the Clients.method() call. I dont see a way to loop through the clients and check the ClientId. The only other I can see to accomplish this is to maybe look at using the groups to keep track of it, but that seemed a little cumbersome, but I was having issues with that as well.
public class TicketHub : Hub
{
static int TotalTickets = 10;
public void GetTicketCount()
{
AddToGroup("ticketClients");
Clients.setTicketCount(TotalTickets);
}
public void BuyTicket()
{
if (TotalTickets > 0)
TotalTickets -= 1;
RemoveFromGroup("ticketClients");
// This will call the method ONLY on the calling client
// Caller.updateTicketCountWithNotification(TotalTickets);
// This will call the method on ALL clients in the group
Clients["ticketClients"].updateTicketCountNotify(TotalTickets);
AddToGroup("ticketClients");
Caller.updateTicketCountDontNotify(TotalTickets);
}
}
javascript code:
<script type="text/javascript">
$(document).ready(function () {
var test = $.connection.test;
$("#btnTest").click(function () {
test.testMethod();
});
test.show = function (text, guid) {
if (guid != test.guid) //notify all clients except the caller
alert(text);
};
$.connection.hub.start(function () { test.start(); });
});
</script>
Class :
public class Test : Hub
{
public void Start()
{
Caller.guid = Guid.NewGuid();
}
public void TestMethod()
{
Clients.show("test", Caller.guid);
}
}
If you want to exclude the caller from the call to the client side method you can use:
Clients.Others.clientSideMethod();
There is also Clients.AllExcept(...) that allows excluding certain people.
Related
I'm trying to learn SignalR by writing a really simple application... it basically sends "Hello" periodically (like the Stock Ticker, but a lot simpler).
Here's my hub:
public class StockTickerHub : Hub
{
public void Hello()
{
var s = StockTicker.stockTicker;
Clients.All.hello();
}
}
...and here's the code that is supposed to periodically send the messages:
public class StockTicker
{
public static StockTicker stockTicker = new StockTicker();
private Thread thread;
public StockTicker()
{
var stockTickerHub = GlobalHost.ConnectionManager.GetHubContext<StockTickerHub>();
this.thread = new Thread(() =>
{
while (true)
{
stockTickerHub.Clients.All().hello();
Thread.Sleep(1000);
}
}
);
this.thread.Start();
}
}
I'm getting a RuntimeBinderException at stockTickerHub.Clients.All().hello();. It says:
An unhandled exception of type 'Microsoft.CSharp.RuntimeBinder.RuntimeBinderException' occurred in System.Core.dll
Additional information: Cannot invoke a non-delegate type
What am I doing wrong?
Client-side JavaScript is below, just in case you need to replicate this.
<script type="text/javascript">
$(function () {
var chat = $.connection.stockTickerHub;
chat.client.hello = function () {
$("#log").append("Hello");
}
$.connection.hub.start().done(function () {
chat.server.hello();
});
});
</script>
Simply change:
stockTickerHub.Clients.All().hello();
to:
stockTickerHub.Clients.All.hello();
The debugger should have already tell you this error. I tried your code after the update. It is working.
A remark on the code design:
I wouldn't start a new sending thread in the hello event, that would start one every time this method is invoked by any client. I don't think that's what you want to do. As a smoother example you could start the ticker in Startup class. (If you want a ticker per connection override OnConnected, get the client's connection id and give them separate tickers...)
Hope everyone is well.
I'm using MVC C# , AspNet.Identities and have a fully functional Account controller.
I recently introduced a basic SignalR Hub to the project, I want to log the user out once he disconnects from the Hub. My idea is to call the LogOff method from the Account Controller.
The Hub is really simple, infact I've taken this from a video by Scott Hanselman if I'm not mistaken. Just the hitCounter part...Now I'm trying to add in the logoff() functionality.
Here's what I've got so far.
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult LogOff()
{
AuthenticationManager.SignOut();
return RedirectToAction("Welcome", "Home");
}//this is in my account controller
[Authorize]
[HubName("hitCounter")]
public class GameplayHub : Hub
{
private static int intCounter = 0;
public void RecordHit()
{
intCounter += 1;
this.Clients.All.onHitRecorded(intCounter);
}
public override System.Threading.Tasks.Task OnDisconnected(bool stopCalled)
{
Final.Controllers.AccountController obj = new Final.Controllers.AccountController();
intCounter -= 1;
this.Clients.All.onHitRecorded(intCounter);
this.Clients.Caller.onHitRecorded(obj.LogOff());
obj.LogOff();
return base.OnDisconnected(stopCalled);
}
}//this is the hub
<div id="hitCount" style="font-size:50px;"></div>
<script src="~/Scripts/jquery-1.6.4.js"></script>
<script src="~/Scripts/jquery.signalR-2.1.1.js"></script>
<script src="/signalr/hubs"></script>
<script>
$(function() {
var con=$.hubConnection();
var hub=con.createHubProxy('hitCounter');
hub.on('onHitRecorded', function (i) {
$('#hitCount').text(i);
});
con.start(function() {
hub.invoke('recordHit');
});
})
</script>//My view...just shows how many people active at that point...
The amount of people active, shows correctly. What I'm trying to do in my app is, if a user in on 2 tabs, and he closes one, he must be logged off on both.
Any help will be appreciated! Thanks :)
Unfortuntelny it is not going to work. Logging off user is done by removing cookie which has to be done by browser. SignalR runs your disconnected handler after tab was already closed, so you can not tell browser to delete cookie.
The solution that could work is to force redirect to log off page on the second tab opened by user.
Pseudocode:
In SignalR hub:
Task OnDisconnected()
{
var otherTab = FindOtherTabWithUser();
otherTab.forceLogOff();
}
In JavaScript:
forceLogOff = function() { window.location.href = '/logoff'; }
SignalR does not have the ability to have client methods which returns a value. So I am trying to create a helper class to make this possible.
So this is what I am trying to do:
Server side: Call client method and provide unique request id Client(clientId).GetValue(requestId)
Server side: Save requestId and wait for answer using ManualResetEvent
Client side: Inside void GetValue(Guid requestId) call server method hubProxy.Invoke("GetValueFinished", requestId, 10)
Server side: find waiting method by requestId => set return value => set signal
Server side: Method not longer waiting vor ManualResetEvent and returns retrieved value.
I am able to get it work unfortunately. Here is my code:
public static class MethodHandler
{
private static ConcurrentDictionary<Guid, ReturnWaiter> runningMethodWaiters = new ConcurrentDictionary<Guid,ReturnWaiter>();
public static TResult GetValue<TResult>(Action<Guid> requestValue)
{
Guid key = Guid.NewGuid();
ReturnWaiter returnWaiter = new ReturnWaiter(key);
runningMethodWaiters.TryAdd(key, returnWaiter);
requestValue.Invoke(key);
returnWaiter.Signal.WaitOne();
return (TResult)returnWaiter.Value;
}
public static void GetValueResult(Guid key, object value)
{
ReturnWaiter waiter;
if (runningMethodWaiters.TryRemove(key, out waiter))
{
waiter.Value = value;
}
}
}
internal class ReturnWaiter
{
private ManualResetEvent _signal = new ManualResetEvent(false);
public ManualResetEvent Signal { get { return _signal; } }
public Guid Key {get; private set;}
public ReturnWaiter(Guid key)
{
Key = key;
}
private object _value;
public object Value
{
get { return _value; }
set
{
_value = value;
Signal.Set();
}
}
}
Using this MethodHandler class I need to have two method server side:
public int GetValue(string clientId)
{
return MethodHandler.GetValue<int>(key => Clients(clientId).Client.GetValue(key));
}
public void GetValueResult(Guid key, object value)
{
MethodHandler.GetValueResult(key, value);
}
Client side implementation is like this:
// Method registration
_hubProxy.On("GetValue", new Action<Guid>(GetValue));
public void GetValue(Guid requestId)
{
int result = 10;
_hubConnection.Invoke("GetValueResult", requestId, result);
}
PROBLEM:
if I call server side GetValue("clientid"). The client method will not be invoked. If I comment out returnWaiter.Signal.WaitOne();, client side GetValue is called and server side GetValueResult is called. But of course this time the method has already returned.
I thought is has to do with the ManualResetEvent but even using while(!returnWaiter.HasValue) Thread.Sleep(100); will not fix this issue.
Any ideas how to fix this issue?
Thanks in advance!
First, I think that, rather than asking for help in how to make it synchronous, it would be best if you just told us what it is you're trying to do so we could suggest a proper approach to do it.
You don't show your MethodHandler::Retrieve method, but I can guess pretty much what it looks like and it's not even the real problem. I have to tell you in the nicest possible way that this is a really bad idea. It will simply never scale. This would only work with a single SignalR server instance because you're relying on machine specific resources (e.g. kernel objects behind the ManualResetEvent) to provide the blocking. Maybe you don't need to scale beyond one server to meet your requirements, but this still a terrible waste of resources even on a single server.
You're actually on the right track with the client calling back with the requestId as a correlating identifier. Why can't you use that correlation to resume logical execution of whatever process you are in the middle of on the server side? That way no resources are held around while waiting for the message to be delivered to the client, processed and then the follow up message, GetValueResult in your sample, to be sent back a the server instance.
Problem solved:
The problem only occured in Hub.OnConnected and Hub.OnDisconnected. I don't have an exact explanation why, but probably these methods must be able to finish before it will handle your method call to the client.
So I changed code:
public override Task OnConnected()
{
// NOT WORKING
Debug.Print(MethodHandler.GetValue<int>(key => Clients(Context.ConnectionId).Client.GetValue(key)));
// WORKING
new Thread(() => Debug.Print(MethodHandler.GetValue<int>(key => Clients(Context.ConnectionId).Client.GetValue(key)))).Start();
return base.OnConnected();
}
I am trying out SignalR, and i don't quite understand how to call methods from my client in a way that it calls the same hub.
i have two methods in my hub:
private ctlDataManager myManager;
public void StartConnection()
{
myManager = new ctlDataManager("test");
myManager.UpdateItemEvent += myManager_UpdateItemEvent;
myManager.Connect();
}
public void StopConnection()
{
myManager.Disconnect();
}
And in my client i try to call them like this:
var notificationHub = $.connection.notificationHub;
$.connection.hub.start()
.done(function (state) {
$("#submit").click(function (e) {
e.preventDefault();
notificationHub.server.startConnection();
return false;
});
$("#stop").click(function (e) {
e.preventDefault();
notificationHub.server.stopConnection();
return false;
});
});
Now when i click on the start button it works fine it starts it and receives data too.
But when i click the stop button it throws an instance of an object error.
It appears that 'myManager' is null. It's almost as a new hub were open. Naturally i need it to be the same one as i need to close the connection.
How can i do that?
From my understanding, the server-side hub class is not persisted. Therefore, the myManager object is created with each method call from a client. My advice would be to declare myManager elsewhere in your application that you can assure 100% up-time, and have your server-side hub methods communicate with it that way.
One way for you to verify this is to debug the constructor of your hub class. You will notice that it is called for every client->server-side method call.
I seem to be having a problem calling:
Clients.Others.SomeJavascriptFunction;
When I use
GlobalHost.ConnectionManager.GetHubContext("MyHub");
I seem to be only able to get this to work within a Hub.
Can anybody shed some light on this.
Regards
Mike
Update
After David's comment
I found that I could do the following:
public class MyHub1 : Hub
{
public static HubConnectionContext MyProperty { get; set; }
public void Start()
{
MyProperty = Clients;
}
}
Then call Start in my js
$.connection.hub.start().done(function () {
sig.server.start();
});
Which then allows me to call my function from my api controller
[HttpPost]
public SaveResult SaveChanges(JObject saveBundle) {
var changes = _contextProvider.SaveChanges(saveBundle);
var stuff = MyHub1.MyProperty;
stuff.Others.refreshToDos();
return changes;
}
Maybe a complete hack but seems to work.
Can anyone see any problems with this?
Others only makes sense when you have a connection id to exclude. Others is shorthand for Clients.AllExcept(Context.ConnectionId). When you're outside the hub there's no current connection id so you can't use Others.
You need to pass the connection id from the client to the API to want to use to do AllExcept.