From d1868287dbb5eb74c84ef82146ae890dae47ace3 Mon Sep 17 00:00:00 2001
From: "Tim St. Clair" <stclair@google.com>
Date: Fri, 6 May 2016 19:31:36 -0700
Subject: [PATCH] Clean up docker root dir

---
 container/docker/client.go  |  8 ++++----
 container/docker/factory.go | 33 +++++++++++++++++++--------------
 2 files changed, 23 insertions(+), 18 deletions(-)

diff --git a/container/docker/client.go b/container/docker/client.go
index 0b0b32cf..b05724cd 100644
--- a/container/docker/client.go
+++ b/container/docker/client.go
@@ -24,13 +24,13 @@ import (
 )
 
 var (
-	dockerClient    *dclient.Client
-	dockerClientErr error
-	once            sync.Once
+	dockerClient     *dclient.Client
+	dockerClientErr  error
+	dockerClientOnce sync.Once
 )
 
 func Client() (*dclient.Client, error) {
-	once.Do(func() {
+	dockerClientOnce.Do(func() {
 		dockerClient, dockerClientErr = dclient.NewClient(*ArgDockerEndpoint, "", nil, nil)
 	})
 	return dockerClient, dockerClientErr
diff --git a/container/docker/factory.go b/container/docker/factory.go
index 93089beb..7708aacf 100644
--- a/container/docker/factory.go
+++ b/container/docker/factory.go
@@ -20,6 +20,7 @@ import (
 	"path"
 	"regexp"
 	"strings"
+	"sync"
 
 	"github.com/google/cadvisor/container"
 	"github.com/google/cadvisor/container/libcontainer"
@@ -34,12 +35,7 @@ import (
 var ArgDockerEndpoint = flag.String("docker", "unix:///var/run/docker.sock", "docker endpoint")
 
 // The namespace under which Docker aliases are unique.
-var DockerNamespace = "docker"
-
-// Basepath to all container specific information that libcontainer stores.
-// TODO: Deprecate this flag
-var dockerRootDir = flag.String("docker_root", "/var/lib/docker", "Absolute path to the Docker state root directory (default: /var/lib/docker)")
-var dockerRunDir = flag.String("docker_run", "/var/run/docker", "Absolute path to the Docker run directory (default: /var/run/docker)")
+const DockerNamespace = "docker"
 
 // Regexp that identifies docker cgroups, containers started with
 // --cgroup-parent have another prefix than 'docker'
@@ -47,12 +43,25 @@ var dockerCgroupRegexp = regexp.MustCompile(`([a-z0-9]{64})`)
 
 var dockerEnvWhitelist = flag.String("docker_env_metadata_whitelist", "", "a comma-separated list of environment variable keys that needs to be collected for docker containers")
 
-const (
-	dockerRootDirKey = "Root Dir"
+var (
+	// Basepath to all container specific information that libcontainer stores.
+	dockerRootDir string
+
+	dockerRootDirFlag = flag.String("docker_root", "/var/lib/docker", "DEPRECATED: docker root is read from docker info (this is a fallback, default: /var/lib/docker)")
+
+	dockerRootDirOnce sync.Once
 )
 
 func RootDir() string {
-	return *dockerRootDir
+	dockerRootDirOnce.Do(func() {
+		status, err := Status()
+		if err == nil && status.RootDir != "" {
+			dockerRootDir = status.RootDir
+		} else {
+			dockerRootDir = *dockerRootDirFlag
+		}
+	})
+	return dockerRootDir
 }
 
 type storageDriver string
@@ -172,10 +181,6 @@ func Register(factory info.MachineInfoFactory, fsInfo fs.FsInfo, ignoreMetrics c
 	// Version already validated above, assume no error here.
 	dockerVersion, _ := parseDockerVersion(dockerInfo.ServerVersion)
 
-	storageDir := dockerInfo.DockerRootDir
-	if storageDir == "" {
-		storageDir = *dockerRootDir
-	}
 	cgroupSubsystems, err := libcontainer.GetCgroupSubsystems()
 	if err != nil {
 		return fmt.Errorf("failed to get cgroup subsystems: %v", err)
@@ -189,7 +194,7 @@ func Register(factory info.MachineInfoFactory, fsInfo fs.FsInfo, ignoreMetrics c
 		fsInfo:             fsInfo,
 		machineInfoFactory: factory,
 		storageDriver:      storageDriver(dockerInfo.Driver),
-		storageDir:         storageDir,
+		storageDir:         RootDir(),
 		ignoreMetrics:      ignoreMetrics,
 	}