SignalR in MVC skewing Application Insights - asp.net-mvc

Question

We just started using SignalR in an MVC application and now we're getting a bunch of alerts due to high average response time. I suspect this to be misleading as the application isn't experiencing performance degradation. It appears that SignalR uses this URL to make a connection. This url not a controller/action of the project and just the built in SignalR code in the js file. jquery.signalR-2.2.1.js is the file. I suspect that it is just leaving the websocket connection open while they are on this page and it's skewing our numbers. Is this accurate? If so, is there a way to filter it out of the application insights?
Here is the counter. Is this the expected behavior?
Here is the signalR jquery code where it builds it's url:
// BUG #2953: The url needs to be same otherwise it will cause a memory leak
getUrl: function (connection, transport, reconnecting, poll, ajaxPost) {
/// <summary>Gets the url for making a GET based connect request</summary>
var baseUrl = transport === "webSockets" ? "" : connection.baseUrl,
url = baseUrl + connection.appRelativeUrl,
qs = "transport=" + transport;
if (!ajaxPost && connection.groupsToken) {
qs += "&groupsToken=" + window.encodeURIComponent(connection.groupsToken);
}
if (!reconnecting) {
url += "/connect";
} else {
if (poll) {
// longPolling transport specific
url += "/poll";
} else {
url += "/reconnect";
}
if (!ajaxPost && connection.messageId) {
qs += "&messageId=" + window.encodeURIComponent(connection.messageId);
}
}
url += "?" + qs;
url = transportLogic.prepareQueryString(connection, url);
if (!ajaxPost) {
url += "&tid=" + Math.floor(Math.random() * 11);
}
return url;
},

Answer 1

I fixed this by following the instructions on https://learn.microsoft.com/en-us/azure/application-insights/app-insights-api-filtering-sampling:
Update your ApplicationInsights Nuget package to 2.0.0 or later.
Create a class implementing ITelemetryProcessor:
public class UnwantedTelemetryFilter : ITelemetryProcessor
{
private ITelemetryProcessor Next { get; set; }
public UnwantedTelemetryFilter(ITelemetryProcessor next)
{
this.Next = next;
}
public void Process(ITelemetry item)
{
var request = item as RequestTelemetry;
if (request != null && request.Name != null)
if (request.Name.Contains("signalr"))
return;
// Send everything else:
this.Next.Process(item);
}
}
Add the processor to your Application_Start() in Global.asax.cs:
var builder = TelemetryConfiguration.Active.TelemetryProcessorChainBuilder;
builder.Use((next) => new UnwantedTelemetryFilter(next));
builder.Build();

Answer 2

if the calls are coming from the C# part of the app, the easiest way is to write a custom telemetry processor:
https://learn.microsoft.com/en-us/azure/application-insights/app-insights-api-filtering-sampling
public void Process(ITelemetry item)
{
var request = item as RequestTelemetry;
if (request != null && request.[some field here].Equals("[some signalr specific check here]", StringComparison.OrdinalIgnoreCase))
{
// To filter out an item, just terminate the chain:
return;
}
// Send everything else:
this.Next.Process(item);
}
and use that to explicitly filter out the signalr calls from being sent
or if the calls are coming from JS, then the telemetry initializer there does a similar thing to filter out telemetry if you return false in the initializer.