Why Does an Infinite Loop Goroutine Block a Go HTTP Server Even with Thread Limits?

Why an Infinite-Loop Goroutine Blocks a Go HTTP Server

Despite setting the number of maximum available threads to 8, starting an infinite-loop goroutine causes the HTTP server to block after a few invocations. This behavior contradicts the assumption that independent threads would prevent blocking.

Explanation:

The Go runtime's scheduler operates in a non-fully pre-emptive manner. While it periodically invokes the scheduler during function calls, an infinite loop without these calls prevents the scheduler from being triggered. This non-preemptive behavior causes the infinite-loop goroutine to consume all available threads, leaving none for the HTTP server.

runtime.LockOSThread()

Adding runtime.LockOSThread() to the infinite loop should have forced its execution on a single thread, isolating it from the HTTP server. However, it fails to resolve the issue.

According to the Go documentation for runtime.LockOSThread(), the targeted empty loop should run in a separate thread, allowing other goroutines to execute concurrently. However, it seems that the empty loop in the example is not sufficiently busy to trigger the thread separation.

Solution:

To address this issue, you can either use a loop with some actual execution logic or manually call runtime.Gosched() within the loop. This will trigger the scheduler and allow other goroutines, including the HTTP server, to resume execution.

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