服务器功能将对所有用户运行一次

Question

Good evening,

In my SignalR application I have a javascript timer that is ran for all users "simultaneously". At the end of this timer, a server function is called, and this is where this problem starts. As the function is called at the end of the timer, every connected user calls it at the same time, which is unnecessary because it will return the same output for all connected users. Being a logically complex function, having the server run it unnecessarily for all users adds up to be a great resource waste.

How can I make it so that it is ran only once (maybe the first time it is called (until the next timer stops))?

Thank you in advance

Answer 1

You could make use of GlobalHost.ConnectionManager.GetHubContext . This will allow you to get any hub context and then trigger Clients.All.YourFunction on that context. That will send send a message to all connected clients subscribed to that hub.

You will need to have a background process that runs every at the time your JavaScript function fires (by the way, relying on all your clients to call a JavaScript function simultaneously is really not a good idea; different client locations and different machine performance will mean they're not likely to be simultaneous).

The following is assuming that you're just running this on a single server. If you're going to be deploying this to a web farm, then you'll need to use a Database value to ensure you don't repeat the same work, or set up a particular server instance to be responsible for doing the calls (otherwise you'll end up with one call per server).

Create a process that runs in the Background (I'm sticking with a simple thread here, I actually use HangFire for this, but this will suffice for the example), eg On App_Start

Thread thread = new Thread(new ThreadStart(YourFunction));
thread.Start();

Then create YourFunction which will be responsible for your client calls:

private bool Cancel = false;

private void YourFunction()
{
    do 
    {
        string foo = "Foo";

        IHubContext context = GlobalHost.ConnectionManager.GetHubContext<YourHub>();
        context.Clients.All.SendYourMessage(foo);

        Thread.Sleep(10000);
    } 
    while(!Cancel)
}

And then on the client, just handle the message from the hub:

youyHub.client.sendYourMessage = function(message)
{
   // message == "Foo"
};