Why Do Infinite-Loop Goroutines Block Go's HTTP Server Despite `runtime.GOMAXPROCS` and `runtime.LockOSThread()`?

Goroutine Infinite Loop Blocking HTTP Server in Go

The Go programming language allows for the creation of concurrent goroutines that run in parallel. However, a recent observation has raised concerns about the behavior of infinite-loop goroutines in HTTP servers.

According to the Go documentation, setting runtime.GOMAXPROCS(8) with 8 CPU cores should allow goroutines to run in parallel without blocking each other. However, this is not the case when using the net/http package. An infinite-loop goroutine seems to block the server after a few requests.

The issue is not limited to the code, as it persists even when runtime.LockOSThread() is added to the infinite-loop goroutine. This is unexpected because runtime.LockOSThread() should ensure that the loop runs in a separate thread, freeing up other goroutines to continue executing.

Explanation

The Go runtime's scheduler is not entirely pre-emptive. In the absence of function calls, as in the case of the infinite-loop code, the scheduler is not triggered. This allows the infinite-loop goroutine to monopolize the CPU and prevent other goroutines from executing.

Solutions

There are a few possible solutions to this issue:

• Add content to the infinite loop: By adding a body or function calls to the infinite loop, the scheduler will be triggered more frequently and other goroutines will have a chance to run.
• Regularly call runtime.Gosched: The runtime.Gosched() function can be used to manually yield the scheduler, allowing other goroutines to execute. This approach may not be ideal for performance-sensitive applications.

It's important to note that runtime.LockOSThread() does not fully isolate the loop in a separate thread. It allows the loop to run on any thread, but the scheduler may still interrupt it if other goroutines require execution.

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