Reuse cached docker client

Fixes #925

container/docker/client.go

@@ -0,0 +1,37 @@
+// 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 /validate content.
+// Validates cadvisor dependencies - kernel, os, docker setup.
+
+package docker
+
+import (
+	"sync"
+
+	dclient "github.com/fsouza/go-dockerclient"
+)
+
+var (
+	dockerClient    *dclient.Client
+	dockerClientErr error
+	once            sync.Once
+)
+
+func Client() (*dclient.Client, error) {
+	once.Do(func() {
+		dockerClient, dockerClientErr = dclient.NewClient(*ArgDockerEndpoint)
+	})
+	return dockerClient, dockerClientErr
+}

container/docker/factory.go

@@ -101,7 +101,7 @@ func (self *dockerFactory) String() string {
 }
 
 func (self *dockerFactory) NewContainerHandler(name string, inHostNamespace bool) (handler container.ContainerHandler, err error) {
-	client, err := docker.NewClient(*ArgDockerEndpoint)
+	client, err := Client()
 	if err != nil {
 		return
 	}
@@ -184,7 +184,7 @@ func parseDockerVersion(full_version_string string) ([]int, error) {
 
 // Register root container before running this function!
 func Register(factory info.MachineInfoFactory, fsInfo fs.FsInfo) error {
-	client, err := docker.NewClient(*ArgDockerEndpoint)
+	client, err := Client()
 	if err != nil {
 		return fmt.Errorf("unable to communicate with docker daemon: %v", err)
 	}

container/docker/handler.go

@@ -335,7 +335,7 @@ func (self *dockerContainerHandler) Exists() bool {
 }
 
 func DockerInfo() (map[string]string, error) {
-	client, err := docker.NewClient(*ArgDockerEndpoint)
+	client, err := Client()
 	if err != nil {
 		return nil, fmt.Errorf("unable to communicate with docker daemon: %v", err)
 	}
@@ -347,7 +347,7 @@ func DockerInfo() (map[string]string, error) {
 }
 
 func DockerImages() ([]docker.APIImages, error) {
-	client, err := docker.NewClient(*ArgDockerEndpoint)
+	client, err := Client()
 	if err != nil {
 		return nil, fmt.Errorf("unable to communicate with docker daemon: %v", err)
 	}

manager/machine.go

@@ -21,7 +21,6 @@ import (
 	"strings"
 	"syscall"
 
-	dclient "github.com/fsouza/go-dockerclient"
 	"github.com/golang/glog"
 	"github.com/google/cadvisor/container/docker"
 	"github.com/google/cadvisor/fs"
@@ -146,7 +145,7 @@ func getContainerOsVersion() string {
 
 func getDockerVersion() string {
 	docker_version := "Unknown"
-	client, err := dclient.NewClient(*docker.ArgDockerEndpoint)
+	client, err := docker.Client()
 	if err == nil {
 		version, err := client.Version()
 		if err == nil {

validate/validate.go

@@ -19,15 +19,15 @@ package validate
 
 import (
 	"fmt"
-	"github.com/google/cadvisor/manager"
 	"io/ioutil"
 	"log"
 	"net/http"
 	"path"
 	"strings"
 
+	"github.com/google/cadvisor/manager"
+
 	"github.com/docker/libcontainer/cgroups"
-	dclient "github.com/fsouza/go-dockerclient"
 	"github.com/google/cadvisor/container/docker"
 	"github.com/google/cadvisor/utils"
 )
@@ -185,7 +185,7 @@ func validateCgroups() (string, string) {
 }
 
 func validateDockerInfo() (string, string) {
-	client, err := dclient.NewClient(*docker.ArgDockerEndpoint)
+	client, err := docker.Client()
 	if err == nil {
 		info, err := client.Info()
 		if err == nil {