How can I dump all a Go process's stacks without killing it?

Question

A Go process is running. I want to

1. dump a stack trace for each of its goroutines
2. from the outside, without depending on anything I add to its source c

Answer 1

You can set up a handler like that using code something like this:

import (
    "fmt"
    "os"
    "os/signal"
    "runtime"
    "syscall"
)

func main() {
    sigChan := make(chan os.Signal)
    go func() {
        stacktrace := make([]byte, 8192)
        for _ = range sigChan {
            length := runtime.Stack(stacktrace, true)
            fmt.Println(string(stacktrace[:length]))
        }
    }()
    signal.Notify(sigChan, syscall.SIGQUIT)


    ...
}

The SIGQUIT signal will now be caught and sent to the given channel. The runtime.Stack function is then used to format the stack trace into a prepared buffer (if it is larger than the buffer, it will be truncated), and then printed.