From dd8345ab321a714693536e064911ce442f1ed401 Mon Sep 17 00:00:00 2001
From: Vishnu kannan <vishnuk@google.com>
Date: Thu, 8 Oct 2015 11:21:38 -0700
Subject: [PATCH] Perform separate housekeeping for docker container filesystem
 stats.

---
 container/docker/fsHandler.go | 109 ++++++++++++++++++++++++++++++++++
 container/docker/handler.go   |  40 ++++---------
 2 files changed, 119 insertions(+), 30 deletions(-)
 create mode 100644 container/docker/fsHandler.go

diff --git a/container/docker/fsHandler.go b/container/docker/fsHandler.go
new file mode 100644
index 00000000..b55634a7
--- /dev/null
+++ b/container/docker/fsHandler.go
@@ -0,0 +1,109 @@
+// Copyright 2015 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Handler for Docker containers.
+package docker
+
+import (
+	"sync"
+	"time"
+
+	"github.com/golang/glog"
+	"github.com/google/cadvisor/fs"
+)
+
+type fsHandler interface {
+	start()
+	usage() uint64
+	stop()
+}
+
+type realFsHandler struct {
+	sync.RWMutex
+	lastUpdate  time.Time
+	usageBytes  uint64
+	period      time.Duration
+	storageDirs []string
+	fsInfo      fs.FsInfo
+	// Tells the container to stop.
+	stopChan chan struct{}
+}
+
+const longDu = time.Second
+
+var _ fsHandler = &realFsHandler{}
+
+func newFsHandler(period time.Duration, storageDirs []string, fsInfo fs.FsInfo) fsHandler {
+	return &realFsHandler{
+		lastUpdate:  time.Time{},
+		usageBytes:  0,
+		period:      period,
+		storageDirs: storageDirs,
+		fsInfo:      fsInfo,
+		stopChan:    make(chan struct{}, 1),
+	}
+}
+
+func (fh *realFsHandler) needsUpdate() bool {
+	return time.Now().After(fh.lastUpdate.Add(fh.period))
+}
+
+func (fh *realFsHandler) update() error {
+	var usage uint64
+	for _, dir := range fh.storageDirs {
+		// TODO(Vishh): Add support for external mounts.
+		dirUsage, err := fh.fsInfo.GetDirUsage(dir)
+		if err != nil {
+			return err
+		}
+		usage += dirUsage
+	}
+	fh.Lock()
+	defer fh.Unlock()
+	fh.lastUpdate = time.Now()
+	fh.usageBytes = usage
+	return nil
+}
+
+func (fh *realFsHandler) trackUsage() {
+	for {
+		start := time.Now()
+		if _, ok := <-fh.stopChan; !ok {
+			return
+		}
+		if err := fh.update(); err != nil {
+			glog.V(2).Infof("failed to collect filesystem stats - %v", err)
+		}
+		duration := time.Since(start)
+		if duration > longDu {
+			glog.V(3).Infof("`du` on following dirs took %v: %v", duration, fh.storageDirs)
+		}
+		next := start.Add(fh.period)
+		time.Sleep(next.Sub(time.Now()))
+	}
+}
+
+func (fh *realFsHandler) start() {
+	go fh.trackUsage()
+}
+
+func (fh *realFsHandler) stop() {
+	close(fh.stopChan)
+}
+
+func (fh *realFsHandler) usage() uint64 {
+	fh.RLock()
+	defer fh.RUnlock()
+	return fh.usageBytes
+}
diff --git a/container/docker/handler.go b/container/docker/handler.go
index 332c4f12..6ae205a4 100644
--- a/container/docker/handler.go
+++ b/container/docker/handler.go
@@ -38,21 +38,6 @@ import (
 // aufs/mnt contains the mount points used to compose the rootfs. Hence it is also ignored.
 var pathToAufsDir = "aufs/diff"
 
-type fsHandler struct {
-	lastUpdate time.Time
-	usageBytes uint64
-	frequency  time.Duration
-}
-
-func (fh *fsHandler) needsUpdate() bool {
-	return time.Now().After(fh.lastUpdate.Add(fh.frequency))
-}
-
-func (fh *fsHandler) update(usage uint64) {
-	fh.lastUpdate = time.Now()
-	fh.usageBytes = usage
-}
-
 type dockerContainerHandler struct {
 	client             *docker.Client
 	name               string
@@ -132,6 +117,9 @@ func newDockerContainerHandler(
 	}
 
 	id := ContainerNameToDockerId(name)
+
+	storageDirs := []string{path.Join(*dockerRootDir, pathToAufsDir, id)}
+
 	handler := &dockerContainerHandler{
 		id:                 id,
 		client:             client,
@@ -142,9 +130,13 @@ func newDockerContainerHandler(
 		usesAufsDriver:     usesAufsDriver,
 		fsInfo:             fsInfo,
 		rootFs:             rootFs,
-		fsHandler:          fsHandler{lastUpdate: time.Time{}, usageBytes: 0, frequency: time.Minute},
+		storageDirs:        storageDirs,
+		fsHandler:          newFsHandler(time.Minute, storageDirs, fsInfo),
+	}
+
+	if usesAufsDriver {
+		handler.fsHandler.start()
 	}
-	handler.storageDirs = append(handler.storageDirs, path.Join(*dockerRootDir, pathToAufsDir, id))
 
 	// We assume that if Inspect fails then the container is not known to docker.
 	ctnr, err := client.InspectContainer(id)
@@ -274,19 +266,7 @@ func (self *dockerContainerHandler) getFsStats(stats *info.ContainerStats) error
 
 	fsStat := info.FsStats{Device: deviceInfo.Device, Limit: limit}
 
-	var usage uint64 = self.fsHandler.usageBytes
-	if self.fsHandler.needsUpdate() {
-		for _, dir := range self.storageDirs {
-			// TODO(Vishh): Add support for external mounts.
-			dirUsage, err := self.fsInfo.GetDirUsage(dir)
-			if err != nil {
-				return err
-			}
-			usage += dirUsage
-		}
-		self.fsHandler.update(usage)
-	}
-	fsStat.Usage = usage
+	fsStat.Usage = self.fsHandler.usage()
 	stats.Filesystem = append(stats.Filesystem, fsStat)
 
 	return nil