Server Sent Events or web server (console) can't handle more than 1-2 tabs

This is a very odd issue we’ve been experiencing for awhile, and I always chalked it up to it just being a dev server (localhost) and can’t handle very many requests. It started happening after adding Server Sent Events to our app (roughly).

But it’s gotten to the point where I can’t even load two tabs to do user permission testing in my app. When opening the second tab to localhost:5000, the content and data either doesn’t load, or half-load and spinners just keep spinning. It acts as though it simply can’t handle any more requests.

Like I said it seemed to start after we added server sent events. It’s especially strange because lets say I open two tabs, the first one loads fully, the second is stuck spinning. Then I close the first tab, the second one finishes loading. Is there some setting in ServiceStack Web host or in server sent events that we can change to allow more requests or remove limits?

What do you mean by “acts as though it simply can’t handle more requests”, SSE requests is a long running HTTP connection which isn’t meant to “finish” as it needs to keep the HTTP connection open to be able to send SSE events.

What’s actually happening at the HTTP level? Are other HTTP Requests hanging? What are the response times for other requests? What web server are you seeing this in, both IIS Express and IIS? If it’s a .NET Core App does running against the the Console App (i.e. dotnet run) have the same behaviour?

Also the browsers max concurrent limit per domain could also be related.