Function snapshot

stack/webstack/webstack.go:98–127

snapshot returns a Context based on the snapshot of the stacks of the current process.

(maxmem int, opts *stack.Opts)

// snapshot returns a Context based on the snapshot of the stacks of the
// current process.
func snapshot(maxmem int, opts *stack.Opts) (*stack.Snapshot, error) {
	// We don't know how big the buffer needs to be to collect all the
	// goroutines. Start with 1 MB and try a few times, doubling each time. Give
	// up and use a truncated trace if maxmem is not enough.
	buf := make([]byte, 1<<20)
	if maxmem < len(buf) {
		maxmem = len(buf)
	}
	for i := 0; ; i++ {
		n := runtime.Stack(buf, true)
		if n < len(buf) {
			buf = buf[:n]
			break
		}
		if len(buf) >= maxmem {
			break
		}
		l := len(buf) * 2
		if l > maxmem {
			l = maxmem
		}
		buf = make([]byte, l)
	}
	s, _, err := stack.ScanSnapshot(bytes.NewReader(buf), io.Discard, opts)
	// That's expected.
	if err == io.EOF {
		err = nil
	}
	return s, err
}