Replace non-threadsafe HashSet with ConcurrentDictionary in RequestTrackingTelemetryModule.IsHandlerToFilter

[Mikhail-msft]

Fix Issue # .
Fixes IndexOutOfRangeException:
WAC FrontEnd unhandled exception [0] [ExceptionType:System.IndexOutOfRangeException]
System.IndexOutOfRangeException: Index was outside the bounds of the array.
at System.Collections.Generic.HashSet`1.AddIfNotPresent(T value)
at Microsoft.ApplicationInsights.Web.RequestTrackingTelemetryModule.IsHandlerToFilter(IHttpHandler handler)
at Microsoft.ApplicationInsights.Web.RequestTrackingTelemetryModule.NeedProcessRequest(HttpContext httpContext)
...

• I ran Unit Tests locally.

[cijothomas]

Please use a descriptive title, and explain how this change is fixing the issue.
And modify changelog.md to add one line about this bug fix.

[TimothyMothra]

In general, this looks good to me.
Is HashSet thread safe? I think that was the main reason for using ConcurrentDictionary here.

[cijothomas]

In general, this looks good to me.
Is HashSet thread safe? I think that was the main reason for using ConcurrentDictionary here.

https://stackoverflow.com/a/18923091/2624380

[TimothyMothra]

In general, this looks good to me.
Is HashSet thread safe? I think that was the main reason for using ConcurrentDictionary here.

https://stackoverflow.com/a/18923091/2624380

lol. I was just reading the same article! :)
I haven't seen the exception that @Mikhail-Pranovich referenced, so it would be good to hear what problem he's trying to solve.

[Mikhail-msft]

And modify changelog.md to add one line about this bug fix.

@cijothomas, Do we need to modify it if the fix is within same version? (i.e. this code was not shipped before)

[TimothyMothra]

oooohhhhhhhhhhh. i read this backwards.. it's replacing the HashSet with ConcurrentDictionary. I agree with this change

[jirigregor]

Is there any chance to release this fix in some quicker way then usual several months cycle? I consider it as a critial bug causing all of our application crashing randomly and there is no other way how to fix it than restarting entire application (in IIS). So currently we had to turn off ApplicationInsights completely.

[TimothyMothra]

Hi @jirigregor This fix is available now in our 2.11-beta1 release.

Regarding our release cadence, we currently release something monthly.
Currently, our requirements are that we only ship a patch release if we introduced a regression. NEW bug fixes are picked up in the next version's release cycle.
But I've seen a handful of requests asking for quicker bug fixes. I'll bring this up in our standup today.