How to put the "real" stack trace under the "stacktrace" key, instead of the "msg" key?

Question

Given the following code (copied from here):

     1  package main
     2  
     3  import (
     4      "fmt"
     5  
     6      "github.com/pkg/errors"
     7  
     8      "go.uber.org/zap"
     9  )
    10  
    11  func main() {
    12      logger, _ := zap.NewProduction()
    13      defer logger.Sync()
    14  
    15      sugar := logger.Sugar()
    16      result, err := caller1()
    17      if err != nil {
    18          sugar.Error(err)
    19          return
    20      }
    21      fmt.Println("Result: ", result)
    22  }
    23  
    24  func caller1() (int, error) {
    25      err := caller2()
    26      if err != nil {
    27          return 0, err
    28      }
    29      return 1, nil
    30  }
    31  
    32  func caller2() error {
    33      doSomething()
    34      return caller3()
    35  }
    36  
    37  func caller3() error {
    38      return errors.New("failed")
    39  }
    40  
    41  func doSomething() {}

Since we are using github.com/pkg/errors package, I know that to log the stack trace, just use sugar.Errorf("%+v", err):

$ go run stacktrace.go 2>&1 | jq
{
  "level": "error",
  "ts": 1606501191.539652,
  "caller": "zap/stacktrace.go:18",
  "msg": "failed\nmain.caller3\n\t/Users/quanta/go/src/github.com/quantonganh/zap/stacktrace.go:38\nmain.caller2\n\t/Users/quanta/go/src/github.com/quantonganh/zap/stacktrace.go:34\nmain.caller1\n\t/Users/quanta/go/src/github.com/quantonganh/zap/stacktrace.go:25\nmain.main\n\t/Users/quanta/go/src/github.com/quantonganh/zap/stacktrace.go:16\nruntime.main\n\t/usr/local/Cellar/go/1.15.2/libexec/src/runtime/proc.go:204\nruntime.goexit\n\t/usr/local/Cellar/go/1.15.2/libexec/src/runtime/asm_amd64.s:1374",
  "stacktrace": "main.main\n\t/Users/quanta/go/src/github.com/quantonganh/zap/stacktrace.go:18\nruntime.main\n\t/usr/local/Cellar/go/1.15.2/libexec/src/runtime/proc.go:204"
}

The thing is the stack trace is put under the msg key and the one under the stacktrace is the stack trace of the logging line:

main.main
    /Users/quanta/go/src/github.com/quantonganh/zap/stacktrace.go:18
runtime.main
    /usr/local/Cellar/go/1.15.2/libexec/src/runtime/proc.go:204

not the stack trace of the error:

main.caller3
    /Users/quanta/go/src/github.com/quantonganh/zap/stacktrace.go:38
main.caller2
    /Users/quanta/go/src/github.com/quantonganh/zap/stacktrace.go:34
main.caller1
    /Users/quanta/go/src/github.com/quantonganh/zap/stacktrace.go:25
main.main
    /Users/quanta/go/src/github.com/quantonganh/zap/stacktrace.go:16
runtime.main
    /usr/local/Cellar/go/1.15.2/libexec/src/runtime/proc.go:204
runtime.goexit
    /usr/local/Cellar/go/1.15.2/libexec/src/runtime/asm_amd64.s:1374

Question: how can I log the "real" stack trace under the stacktrace key?

quanta · Answer 1 · 2020-11-28T12:49:04.830

I have looked into the source code and I think we cannot do that.

Log messages are formatted and put under the msg key.

The stack trace is taken from runtime.CallersFrames at the time of logging.

The reason I asked this question is before using %+v to get the complete call stack, I just looked at the "stacktrace" value and wondering:

Why it is missing?
Why it just point to the logging line instead of pointing to the actual error?

How to put the "real" stack trace under the "stacktrace" key, instead of the "msg" key?

1 Answers1