Number of specific go routines running

Question

In go's runtime lib we have NumGoroutine() to return the total number of go routines running at that time. I was wondering if there was a simple way of getting the number of go routines running of a specific function?

Currently I have it telling me I have 1000, or whatever, of all go routines but I would like to know I have 500 go routines running func Foo. Possible? Simple? Shouldn't bother with it?

Answer 1

I'm afraid you have to count the goroutines on your own if you are interested in those numbers. The cheapest way to achieve your goal would be to use the sync/atomic package directly.

import "sync/atomic"

var counter int64

func example() {
    atomic.AddInt64(&counter, 1)
    defer atomic.AddInt64(&counter, -1)

    // ...
}

Use atomic.LoadInt64(&counter) whenever you want to read the current value of the counter.

And it's not uncommon to have a couple of such counters in your program, so that you can monitor it easily. For example, take a look at the CacheStats struct of the recently published groupcache source.