From 159b9e80c4466c948285debb13ecc3acb50b8ace Mon Sep 17 00:00:00 2001
From: Alexander Neumann <alexander@bumpern.de>
Date: Sun, 12 Jul 2015 22:10:01 +0200
Subject: [PATCH] cmd/restic: implement lock refresh

---
 cmd/restic/lock.go | 80 +++++++++++++++++++++++++++++++++++-----------
 cmd/restic/main.go |  6 ++++
 lock.go            |  2 ++
 3 files changed, 70 insertions(+), 18 deletions(-)

diff --git a/cmd/restic/lock.go b/cmd/restic/lock.go
index 389241644..a5bdc3981 100644
--- a/cmd/restic/lock.go
+++ b/cmd/restic/lock.go
@@ -4,14 +4,21 @@ import (
 	"fmt"
 	"os"
 	"os/signal"
+	"sync"
 	"syscall"
+	"time"
 
 	"github.com/restic/restic"
 	"github.com/restic/restic/debug"
 	"github.com/restic/restic/repository"
 )
 
-var globalLocks []*restic.Lock
+var globalLocks struct {
+	locks         []*restic.Lock
+	cancelRefresh chan struct{}
+	refreshWG     sync.WaitGroup
+	sync.Mutex
+}
 
 func lockRepo(repo *repository.Repository) (*restic.Lock, error) {
 	return lockRepository(repo, false)
@@ -29,35 +36,69 @@ func lockRepository(repo *repository.Repository, exclusive bool) (*restic.Lock,
 
 	lock, err := lockFn(repo)
 	if err != nil {
-		if restic.IsAlreadyLocked(err) {
-			tpe := ""
-			if exclusive {
-				tpe = " exclusive"
-			}
-			fmt.Fprintf(os.Stderr, "unable to acquire%s lock for operation:\n", tpe)
-			fmt.Fprintln(os.Stderr, err)
-			fmt.Fprintf(os.Stderr, "\nthe `unlock` command can be used to remove stale locks\n")
-			os.Exit(1)
-		}
-
 		return nil, err
 	}
 
-	globalLocks = append(globalLocks, lock)
+	globalLocks.Lock()
+	if globalLocks.cancelRefresh == nil {
+		debug.Log("main.lockRepository", "start goroutine for lock refresh")
+		globalLocks.cancelRefresh = make(chan struct{})
+		globalLocks.refreshWG = sync.WaitGroup{}
+		globalLocks.refreshWG.Add(1)
+		go refreshLocks(&globalLocks.refreshWG, globalLocks.cancelRefresh)
+	}
+
+	globalLocks.locks = append(globalLocks.locks, lock)
+	globalLocks.Unlock()
 
 	return lock, err
 }
 
+var refreshInterval = 5 * time.Minute
+
+func refreshLocks(wg *sync.WaitGroup, done <-chan struct{}) {
+	debug.Log("main.refreshLocks", "start")
+	defer func() {
+		wg.Done()
+		globalLocks.Lock()
+		globalLocks.cancelRefresh = nil
+		globalLocks.Unlock()
+	}()
+
+	ticker := time.NewTicker(refreshInterval)
+
+	for {
+		select {
+		case <-done:
+			debug.Log("main.refreshLocks", "terminate")
+			return
+		case <-ticker.C:
+			debug.Log("main.refreshLocks", "refreshing locks")
+			globalLocks.Lock()
+			for _, lock := range globalLocks.locks {
+				err := lock.Refresh()
+				if err != nil {
+					fmt.Fprintf(os.Stderr, "unable to refresh lock: %v\n", err)
+				}
+			}
+			globalLocks.Unlock()
+		}
+	}
+}
+
 func unlockRepo(lock *restic.Lock) error {
+	globalLocks.Lock()
+	defer globalLocks.Unlock()
+
 	debug.Log("unlockRepo", "unlocking repository")
 	if err := lock.Unlock(); err != nil {
 		debug.Log("unlockRepo", "error while unlocking: %v", err)
 		return err
 	}
 
-	for i := 0; i < len(globalLocks); i++ {
-		if lock == globalLocks[i] {
-			globalLocks = append(globalLocks[:i], globalLocks[i+1:]...)
+	for i := 0; i < len(globalLocks.locks); i++ {
+		if lock == globalLocks.locks[i] {
+			globalLocks.locks = append(globalLocks.locks[:i], globalLocks.locks[i+1:]...)
 			return nil
 		}
 	}
@@ -66,8 +107,11 @@ func unlockRepo(lock *restic.Lock) error {
 }
 
 func unlockAll() error {
-	debug.Log("unlockAll", "unlocking %d locks", len(globalLocks))
-	for _, lock := range globalLocks {
+	globalLocks.Lock()
+	defer globalLocks.Unlock()
+
+	debug.Log("unlockAll", "unlocking %d locks", len(globalLocks.locks))
+	for _, lock := range globalLocks.locks {
 		if err := lock.Unlock(); err != nil {
 			debug.Log("unlockAll", "error while unlocking: %v", err)
 			return err
diff --git a/cmd/restic/main.go b/cmd/restic/main.go
index 8669ae8d6..3acab925e 100644
--- a/cmd/restic/main.go
+++ b/cmd/restic/main.go
@@ -1,10 +1,12 @@
 package main
 
 import (
+	"fmt"
 	"os"
 	"runtime"
 
 	"github.com/jessevdk/go-flags"
+	"github.com/restic/restic"
 	"github.com/restic/restic/debug"
 )
 
@@ -26,6 +28,10 @@ func main() {
 		os.Exit(0)
 	}
 
+	if restic.IsAlreadyLocked(err) {
+		fmt.Fprintf(os.Stderr, "\nthe `unlock` command can be used to remove stale locks\n")
+	}
+
 	if err != nil {
 		os.Exit(1)
 	}
diff --git a/lock.go b/lock.go
index d4fb990f5..2a30a98b4 100644
--- a/lock.go
+++ b/lock.go
@@ -225,6 +225,7 @@ func (l *Lock) Stale() bool {
 // Refresh refreshes the lock by creating a new file in the backend with a new
 // timestamp. Afterwards the old lock is removed.
 func (l *Lock) Refresh() error {
+	debug.Log("Lock.Refresh", "refreshing lock %v", l.lockID.Str())
 	id, err := l.createLock()
 	if err != nil {
 		return err
@@ -235,6 +236,7 @@ func (l *Lock) Refresh() error {
 		return err
 	}
 
+	debug.Log("Lock.Refresh", "new lock ID %v", id.Str())
 	l.lockID = id
 
 	return nil