Refactor netlink implementation.

This allows us to plug in a scheddebug based interface.

manager/container.go

@@ -44,7 +44,7 @@ type containerData struct {
 	info                 containerInfo
 	storageDriver        storage.StorageDriver
 	lock                 sync.Mutex
-	loadReader           *cpuload.CpuLoadReader
+	loadReader           cpuload.CpuLoadReader
 	housekeepingInterval time.Duration
 	lastUpdatedTime      time.Time
 	lastErrorTime        time.Time
@@ -93,7 +93,7 @@ func (c *containerData) GetInfo() (*containerInfo, error) {
 	return &c.info, nil
 }
 
-func newContainerData(containerName string, driver storage.StorageDriver, handler container.ContainerHandler, loadReader *cpuload.CpuLoadReader, logUsage bool) (*containerData, error) {
+func newContainerData(containerName string, driver storage.StorageDriver, handler container.ContainerHandler, loadReader cpuload.CpuLoadReader, logUsage bool) (*containerData, error) {
 	if driver == nil {
 		return nil, fmt.Errorf("nil storage driver")
 	}

manager/manager.go

@@ -120,7 +120,7 @@ type manager struct {
 	quitChannels           []chan error
 	cadvisorContainer      string
 	dockerContainersRegexp *regexp.Regexp
-	loadReader             *cpuload.CpuLoadReader
+	loadReader             cpuload.CpuLoadReader
 }
 
 // Start the container manager.
@@ -129,9 +129,14 @@ func (self *manager) Start() error {
 	cpuLoadReader, err := cpuload.New()
 	if err != nil {
 		// TODO(rjnagal): Promote to warning once we support cpu load inside namespaces.
-		glog.Infof("could not initialize cpu load reader: %s", err)
+		glog.Infof("Could not initialize cpu load reader: %s", err)
 	} else {
-		self.loadReader = cpuLoadReader
+		err = cpuLoadReader.Start()
+		if err != nil {
+			glog.Warning("Could not start cpu load stat collector: %s", err)
+		} else {
+			self.loadReader = cpuLoadReader
+		}
 	}
 
 	// Create root and then recover all containers.
@@ -176,7 +181,7 @@ func (self *manager) Stop() error {
 	}
 	self.quitChannels = make([]chan error, 0, 2)
 	if self.loadReader != nil {
-		self.loadReader.Close()
+		self.loadReader.Stop()
 		self.loadReader = nil
 	}
 	return nil

utils/cpuload/cpuload.go

@@ -16,58 +16,27 @@ package cpuload
 
 import (
 	"fmt"
-	"os"
 
-	"github.com/golang/glog"
 	"github.com/google/cadvisor/info"
+	"github.com/google/cadvisor/utils/cpuload/netlink"
 )
 
-type CpuLoadReader struct {
+type CpuLoadReader interface {
-	familyId uint16
+	// Start the reader.
-	conn     *Connection
+	Start() error
+
+	// Stop the reader and clean up internal state.
+	Stop()
+
+	// Retrieve Cpu load for a given group.
+	// Path is an absolute filesystem path for a container under CPU cgroup hierarchy.
+	GetCpuLoad(path string) (info.LoadStats, error)
 }
 
-func New() (*CpuLoadReader, error) {
+func New() (CpuLoadReader, error) {
-	conn, err := newConnection()
+	reader, err := netlink.New()
 	if err != nil {
-		return nil, fmt.Errorf("failed to create a new connection: %s", err)
+		return nil, fmt.Errorf("failed to create a netlink-based cpu load reader: %s", err)
 	}
-
+	return reader, nil
-	id, err := getFamilyId(conn)
-	if err != nil {
-		return nil, fmt.Errorf("failed to get netlink family id for task stats: %s", err)
-	}
-	glog.V(2).Infof("Family id for taskstats: %d", id)
-	return &CpuLoadReader{
-		familyId: id,
-		conn:     conn,
-	}, nil
-}
-
-func (self *CpuLoadReader) Close() {
-	if self.conn != nil {
-		self.conn.Close()
-	}
-}
-
-// Returns instantaneous number of running tasks in a group.
-// Caller can use historical data to calculate cpu load.
-// path is an absolute filesystem path for a container under the CPU cgroup hierarchy.
-// NOTE: non-hierarchical load is returned. It does not include load for subcontainers.
-func (self *CpuLoadReader) GetCpuLoad(path string) (info.LoadStats, error) {
-	if len(path) == 0 {
-		return info.LoadStats{}, fmt.Errorf("cgroup path can not be empty!")
-	}
-
-	cfd, err := os.Open(path)
-	if err != nil {
-		return info.LoadStats{}, fmt.Errorf("failed to open cgroup path %s: %q", path, err)
-	}
-
-	stats, err := getLoadStats(self.familyId, cfd.Fd(), self.conn)
-	if err != nil {
-		return info.LoadStats{}, err
-	}
-	glog.V(1).Infof("Task stats for %q: %+v", path, stats)
-	return stats, nil
 }

utils/cpuload/netlink/conn.go

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package cpuload
+package netlink
 
 import (
 	"bufio"

utils/cpuload/netlink/defs.go

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package cpuload
+package netlink
 
 /*
 #include <linux/taskstats.h>

utils/cpuload/netlink/example/example.go

@@ -17,20 +17,20 @@ package main
 import (
 	"log"
 
-	"github.com/google/cadvisor/utils/cpuload"
+	"github.com/google/cadvisor/utils/cpuload/netlink"
 )
 
 func main() {
-	c, err := cpuload.New()
+	n, err := netlink.New()
 	if err != nil {
 		log.Printf("Failed to create cpu load util: %s", err)
 		return
 	}
-	defer c.Close()
+	defer n.Stop()
 
 	paths := []string{"/sys/fs/cgroup/cpu", "/sys/fs/cgroup/cpu/docker"}
 	for _, path := range paths {
-		stats, err := c.GetCpuLoad(path)
+		stats, err := n.GetCpuLoad(path)
 		if err != nil {
 			log.Printf("Error getting cpu load for %q: %s", path, err)
 		}

utils/cpuload/netlink/netlink.go

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package cpuload
+package netlink
 
 import (
 	"bytes"

utils/cpuload/netlink/reader.go

@@ -0,0 +1,78 @@
+// 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.
+
+package netlink
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/golang/glog"
+	"github.com/google/cadvisor/info"
+)
+
+type NetlinkReader struct {
+	familyId uint16
+	conn     *Connection
+}
+
+func New() (*NetlinkReader, error) {
+	conn, err := newConnection()
+	if err != nil {
+		return nil, fmt.Errorf("failed to create a new connection: %s", err)
+	}
+
+	id, err := getFamilyId(conn)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get netlink family id for task stats: %s", err)
+	}
+	glog.V(2).Infof("Family id for taskstats: %d", id)
+	return &NetlinkReader{
+		familyId: id,
+		conn:     conn,
+	}, nil
+}
+
+func (self *NetlinkReader) Stop() {
+	if self.conn != nil {
+		self.conn.Close()
+	}
+}
+
+func (self *NetlinkReader) Start() error {
+	// We do the start setup for netlink in New(). Nothing to do here.
+	return nil
+}
+
+// Returns instantaneous number of running tasks in a group.
+// Caller can use historical data to calculate cpu load.
+// path is an absolute filesystem path for a container under the CPU cgroup hierarchy.
+// NOTE: non-hierarchical load is returned. It does not include load for subcontainers.
+func (self *NetlinkReader) GetCpuLoad(path string) (info.LoadStats, error) {
+	if len(path) == 0 {
+		return info.LoadStats{}, fmt.Errorf("cgroup path can not be empty!")
+	}
+
+	cfd, err := os.Open(path)
+	if err != nil {
+		return info.LoadStats{}, fmt.Errorf("failed to open cgroup path %s: %q", path, err)
+	}
+
+	stats, err := getLoadStats(self.familyId, cfd.Fd(), self.conn)
+	if err != nil {
+		return info.LoadStats{}, err
+	}
+	glog.V(1).Infof("Task stats for %q: %+v", path, stats)
+	return stats, nil
+}