make the logging of stacks in errors an opt-in behavior

Signed-off-by: Michael Demmer <mdemmer@slack-corp.com>

go/vt/vterrors/vterrors.go

@@ -70,6 +70,7 @@
 package vterrors
 
 import (
+	"flag"
 	"fmt"
 	"io"
 
@@ -77,6 +78,12 @@ import (
 	vtrpcpb "vitess.io/vitess/go/vt/proto/vtrpc"
 )
 
+var logErrStacks bool
+
+func init() {
+	flag.BoolVar(&logErrStacks, "logerrstacks", false, "log stack traces in errors")
+}
+
 // New returns an error with the supplied message.
 // New also records the stack trace at the point it was called.
 func New(code vtrpcpb.Code, message string) error {
@@ -122,7 +129,9 @@ func (f *fundamental) Format(s fmt.State, verb rune) {
 	case 'v':
 		panicIfError(io.WriteString(s, "Code: "+f.code.String()+"\n"))
 		panicIfError(io.WriteString(s, f.msg+"\n"))
-		f.stack.Format(s, verb)
+		if logErrStacks {
+			f.stack.Format(s, verb)
+		}
 		return
 	case 's':
 		panicIfError(io.WriteString(s, f.msg))
@@ -198,7 +207,9 @@ func (w *wrapping) Format(s fmt.State, verb rune) {
 	if rune('v') == verb {
 		panicIfError(fmt.Fprintf(s, "%v\n", w.Cause()))
 		panicIfError(io.WriteString(s, w.msg))
-		w.stack.Format(s, verb)
+		if logErrStacks {
+			w.stack.Format(s, verb)
+		}
 		return
 	}