Elastic APM Go Deep Stacktrace

tracer.go

package tracer

import (
	"context"
	"github.com/pkg/errors"
	"go.elastic.co/apm"
	"runtime"
)

// Lifted from github.com/pkg/errors
func callers() errors.StackTrace {
	const depth = 32
	var pcs [depth]uintptr
	n := runtime.Callers(3, pcs[:])
	var st []uintptr = pcs[0:n]

	f := make([]errors.Frame, len(st))
	for i := 0; i < len(f); i++ {
		f[i] = errors.Frame((st)[i])
	}
	return f
}

type unwrappedError struct {
	error
}

type stackTracer interface {
	StackTrace() errors.StackTrace
}

func Unwrap(e error) error {
	return &unwrappedError{error: e}
}

func (u *unwrappedError) Cause() error {
	return u.error
}

func (u *unwrappedError) StackTrace() errors.StackTrace {
	st := callers()

	var last stackTracer
	err := u.error
  // See https://github.com/newrelic/go-agent/blob/c680931e5ab45efd53e933df0350ff469d8c3d24/_integrations/nrpkgerrors/nrpkgerrors.go#L28
	for err != nil {
		if err, ok := err.(stackTracer); ok {
			last = err
		}
		cause, ok := err.(interface {
			Cause() error
		})
		if !ok {
			break
		}
		err = cause.Cause()
	}

	if last == nil {
		return st
	}
	return last.StackTrace()
}

// CaptureError reports an error to APM with the deepest Stacktrace. See https://github.com/elastic/apm-agent-go/issues/423
// Use this instead of apm.CaptureError
func CaptureError(ctx context.Context, err error) *apm.Error {
	return apm.CaptureError(ctx, Unwrap(err))
}