runtime.Stack
- Go course
- Expert
- Lesson 22/34
- 4 min
Learn to get a goroutine's stack trace with Stack.
runtime.Stack
runtime.Stack(buf, all) writes the call stack as text into a buffer. If all is true, every goroutine's stack is written; this is very valuable when diagnosing a stuck service.
buf := make([]byte, 1<<16)
n := runtime.Stack(buf, true)
os.Stderr.Write(buf[:n])For the current goroutine only, debug.Stack() or debug.PrintStack() is shorter.
runtime.Caller
runtime.Caller(skip) returns the caller's file name and line; logging libraries add line information this way:
func nerede() string {
_, dosya, satir, ok := runtime.Caller(1)
if !ok { return "?" }
return fmt.Sprintf("%s:%d", filepath.Base(dosya), satir)
}skip=0 refers to the function calling Caller, 1 to its caller.
Practice Search the stack
Write a function called calisan(); inside it call runtime.Stack(buf, false) with buf := make([]byte, 4096) and return whether the stack text contains "main.calisan" using strings.Contains. Print the result.
Starter code
package main
import (
"fmt"
"runtime"
"strings"
)
func main() {
// buraya yaz
}Sample solution
package main
import (
"fmt"
"runtime"
"strings"
)
func calisan() bool {
buf := make([]byte, 4096)
n := runtime.Stack(buf, false)
return strings.Contains(string(buf[:n]), "main.calisan")
}
func main() {
fmt.Println(calisan())
}Expected output
true
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 How do you get all goroutine stacks of a running Go process without changing code?
- With GOGC=off
- It isn't possible
- By sending SIGQUIT (Ctrl+\) Correct answer
- By sending SIGINT
Explanation: On SIGQUIT the Go runtime writes all goroutine stacks to stderr and exits; GOTRACEBACK=all increases the detail.
2 All goroutines
n := runtime.Stack(buf, ____)n := runtime.Stack(buf, true)Explanation: With the second argument true, every goroutine's stack is written.
3 Tool and output
| Term | Meaning |
|---|---|
runtime.Stack(buf, true) |
All stacks |
debug.Stack() |
Current goroutine |
runtime.Caller(1) |
File and line |
SIGQUIT |
Stack dump and exit |