handle rsync failure gracefully

  - main loop will now gracefully exit when rsync is not found or
  returns anything except 0 or 24.
  - pid unlock works now in this case
  - probably we will need to handle other rsync return codes like 24

Author: sstark

main.go

@@ -97,6 +97,7 @@ func subcmdRun() (ferr error) {
 		var createError error
 	CREATE_LOOP:
 		for {
+			debugf("start of create loop")
 			select {
 			case <-createExit:
 				debugf("gracefully exiting snapshot creation goroutine")
@@ -106,8 +107,18 @@ func subcmdRun() (ferr error) {
 				sn, err := createSnapshot(lastGood)
 				if err != nil || sn == nil {
 					debugf("snapshot creation finally failed (%s), the partial transfer will hopefully be reused", err)
-					//createError = err
-					//go func() { createExit <- true; return }()
+					createError = err
+					go func() {
+						// need to stop the lastGoodTicker here because it could
+						// happen that it will be faster and the create loop would
+						// run again instead of exiting
+						lastGoodOut = nil
+						debugf("subcmdRun: sending createExit")
+						createExit <- true
+						debugf("subcmdRun: createExit sent")
+						return
+					}()
+					time.Sleep(time.Second)
 				}
 				lastGoodIn <- sn
 				debugf("pruning")
@@ -187,7 +198,9 @@ func subcmdRun() (ferr error) {
 			createExit <- true
 			ferr = <-createExitDone
 		}
+	// ferr will hold the error that happened in the CREATE_LOOP
 	case ferr = <-createExitDone:
+		log.Println("-> Rsync exit")
 	}
 	return
 }

rsync.go

@@ -6,6 +6,7 @@ package main
 
 import (
 	"errors"
+	"fmt"
 	"log"
 	"os"
 	"os/exec"
@@ -72,7 +73,8 @@ func createSnapshot(base *snapshot) (*snapshot, error) {
 	cmd := createRsyncCommand(newSn, base)
 	done, err := runRsyncCommand(cmd)
 	if err != nil {
-		log.Fatalln("could not start rsync command:", err)
+		log.Println("could not start rsync command:", err)
+		return nil, err
 	}
 	debugf("rsync started")
 	sigc := make(chan os.Signal, 1)
@@ -113,7 +115,7 @@ func createSnapshot(base *snapshot) (*snapshot, error) {
 					}
 				}
 				if failed {
-					return nil, err
+					return nil, fmt.Errorf("rsync failed: %s", err)
 				}
 			}
 			newSn.transComplete(cl)