lib/fs: add MustStopDirRemover for waiting until pending directories are removed on graceful shutdown

This patch is mainly required for laggy NFS. See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/162

app/vminsert/main.go

@@ -16,6 +16,7 @@ import (
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/auth"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/buildinfo"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/flagutil"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/fs"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/httpserver"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/procutil"
@@ -88,6 +89,8 @@ func main() {
 	netstorage.Stop()
 	logger.Infof("successfully stopped netstorage in %s", time.Since(startTime))
 
+	fs.MustStopDirRemover()
+
 	logger.Infof("the vminsert has been stopped")
 }
 

app/vmselect/main.go

@@ -76,6 +76,8 @@ func main() {
 	}
 	logger.Infof("successfully stopped netstorage in %s", time.Since(startTime))
 
+	fs.MustStopDirRemover()
+
 	logger.Infof("the vmselect has been stopped")
 }
 

app/vmstorage/main.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmstorage/transport"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/buildinfo"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/fs"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/httpserver"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/procutil"
@@ -76,6 +77,8 @@ func main() {
 	strg.MustClose()
 	logger.Infof("successfully closed the storage in %s", time.Since(startTime))
 
+	fs.MustStopDirRemover()
+
 	logger.Infof("the vmstorage has been stopped")
 }
 

lib/fs/dir_remover.go

@@ -0,0 +1,111 @@
+package fs
+
+import (
+	"os"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
+	"github.com/VictoriaMetrics/metrics"
+)
+
+func mustRemoveAll(path string) bool {
+	err := os.RemoveAll(path)
+	if err == nil {
+		// Make sure the parent directory doesn't contain references
+		// to the current directory.
+		mustSyncParentDirIfExists(path)
+		return true
+	}
+	if !isTemporaryNFSError(err) {
+		logger.Panicf("FATAL: cannot remove %q: %s", path, err)
+	}
+	// NFS prevents from removing directories with open files.
+	// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/61 .
+	// Schedule for later directory removal.
+	nfsDirRemoveFailedAttempts.Inc()
+	select {
+	case removeDirCh <- path:
+	default:
+		logger.Panicf("FATAL: cannot schedule %s for removal, since the removal queue is full (%d entries)", path, cap(removeDirCh))
+	}
+	return false
+}
+
+var nfsDirRemoveFailedAttempts = metrics.NewCounter(`vm_nfs_dir_remove_failed_attempts_total`)
+
+var removeDirCh = make(chan string, 1024)
+
+func dirRemover() {
+	const minSleepTime = 100 * time.Millisecond
+	const maxSleepTime = time.Second
+	sleepTime := minSleepTime
+	for {
+		var path string
+		select {
+		case path = <-removeDirCh:
+		default:
+			if atomic.LoadUint64(&stopDirRemover) != 0 {
+				return
+			}
+			time.Sleep(minSleepTime)
+			continue
+		}
+		if mustRemoveAll(path) {
+			sleepTime = minSleepTime
+			continue
+		}
+
+		// Couldn't remove the directory at the path because of NFS lock.
+		// Sleep for a while and try again.
+		// Do not limit the amount of time required for deleting the directory,
+		// since this may break on laggy NFS.
+		// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/162 .
+		time.Sleep(sleepTime)
+		if sleepTime < maxSleepTime {
+			sleepTime *= 2
+		} else {
+			logger.Errorf("failed to remove directory %q due to NFS lock; retrying later", path)
+		}
+	}
+}
+
+func isTemporaryNFSError(err error) bool {
+	// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/61 for details.
+	errStr := err.Error()
+	return strings.Contains(errStr, "directory not empty") || strings.Contains(errStr, "device or resource busy")
+}
+
+var dirRemoverWG sync.WaitGroup
+var stopDirRemover uint64
+
+func init() {
+	dirRemoverWG.Add(1)
+	go func() {
+		defer dirRemoverWG.Done()
+		dirRemover()
+	}()
+}
+
+// MustStopDirRemover must be called in the end of graceful shutdown
+// in order to wait for removing the remaining directories from removeDirCh.
+//
+// It is expected that nobody calls MustRemoveAll when MustStopDirRemover
+// is called.
+func MustStopDirRemover() {
+	atomic.StoreUint64(&stopDirRemover, 1)
+	doneCh := make(chan struct{})
+	go func() {
+		dirRemoverWG.Wait()
+		close(doneCh)
+	}()
+	const maxWaitTime = 5 * time.Second
+	select {
+	case <-doneCh:
+		return
+	case <-time.After(maxWaitTime):
+		logger.Panicf("FATAL: cannot stop dirRemover in %s", maxWaitTime)
+	}
+}

lib/fs/fs.go

@@ -6,9 +6,7 @@ import (
 	"os"
 	"path/filepath"
 	"regexp"
-	"strings"
 	"sync/atomic"
-	"time"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/filestream"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
@@ -251,67 +249,6 @@ func MustRemoveAll(path string) {
 	_ = mustRemoveAll(path)
 }
 
-func mustRemoveAll(path string) bool {
-	err := os.RemoveAll(path)
-	if err == nil {
-		// Make sure the parent directory doesn't contain references
-		// to the current directory.
-		mustSyncParentDirIfExists(path)
-		return true
-	}
-	if !isTemporaryNFSError(err) {
-		logger.Panicf("FATAL: cannot remove %q: %s", path, err)
-	}
-	// NFS prevents from removing directories with open files.
-	// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/61 .
-	// Schedule for later directory removal.
-	nfsDirRemoveFailedAttempts.Inc()
-	select {
-	case removeDirCh <- path:
-	default:
-		logger.Panicf("FATAL: cannot schedule %s for removal, since the removal queue is full (%d entries)", path, cap(removeDirCh))
-	}
-	return false
-}
-
-var nfsDirRemoveFailedAttempts = metrics.NewCounter(`vm_nfs_dir_remove_failed_attempts_total`)
-
-var removeDirCh = make(chan string, 1024)
-
-func dirRemover() {
-	const minSleepTime = 100 * time.Millisecond
-	const maxSleepTime = time.Second
-	sleepTime := minSleepTime
-	for path := range removeDirCh {
-		if mustRemoveAll(path) {
-			sleepTime = minSleepTime
-			continue
-		}
-
-		// Couldn't remove the directory at the path because of NFS lock.
-		// Sleep for a while and try again.
-		// Do not limit the amount of time required for deleting the directory,
-		// since this may break on laggy NFS.
-		// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/162 .
-		time.Sleep(sleepTime)
-		if sleepTime < maxSleepTime {
-			sleepTime *= 2
-		} else {
-			logger.Errorf("failed to remove directory %q due to NFS lock; retrying later", path)
-		}
-	}
-}
-
-func isTemporaryNFSError(err error) bool {
-	// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/61 for details.
-	errStr := err.Error()
-	return strings.Contains(errStr, "directory not empty") || strings.Contains(errStr, "device or resource busy")
-}
-
-func init() {
-	go dirRemover()
-}
-
 // HardLinkFiles makes hard links for all the files from srcDir in dstDir.
 func HardLinkFiles(srcDir, dstDir string) error {
 	if err := mkdirSync(dstDir); err != nil {