Merge pull request #34 from mistifyio/MIST-581

MIST-581 Add debug logging before and after running external zfs command

Author: bbickerton

utils.go

@@ -8,6 +8,8 @@ import (
 	"regexp"
 	"strconv"
 	"strings"
+
+	"code.google.com/p/go-uuid/uuid"
 )
 
 type command struct {
@@ -34,16 +36,17 @@ func (c *command) Run(arg ...string) ([][]string, error) {
 	}
 	cmd.Stderr = &stderr
 
-	debug := strings.Join([]string{cmd.Path, strings.Join(cmd.Args, " ")}, " ")
-	if logger != nil {
-		logger.Log(cmd.Args)
-	}
+	id := uuid.New()
+	joinedArgs := strings.Join(cmd.Args, " ")
+
+	logger.Log([]string{"ID:" + id, "START", joinedArgs})
 	err := cmd.Run()
+	logger.Log([]string{"ID:" + id, "FINISH"})
 
 	if err != nil {
 		return nil, &Error{
 			Err:    err,
-			Debug:  debug,
+			Debug:  strings.Join([]string{cmd.Path, joinedArgs}, " "),
 			Stderr: stderr.String(),
 		}
 	}

zfs.go

@@ -92,12 +92,20 @@ type Logger interface {
 	Log(cmd []string)
 }
 
-var logger Logger
+type defaultLogger struct{}
+
+func (*defaultLogger) Log(cmd []string) {
+	return
+}
+
+var logger Logger = &defaultLogger{}
 
 // SetLogger set a log handler to log all commands including arguments before
 // they are executed
 func SetLogger(l Logger) {
-	logger = l
+	if l != nil {
+		logger = l
+	}
 }
 
 // zfs is a helper function to wrap typical calls to zfs.