cAdvisor 容器数据采集

cAdvisor 代码托管地址

• 代码入口： github.com/google/cadvisor/cadvisor.go
• API handler: github.com/google/cadvisor/api/handler.go
• 基于 tag： v0.19.2

# github.com/google/cadvisor/cadvisor.go
... ...
73     containerManager, err := manager.New(memoryStorage, sysFs, *maxHousekeepingInterval, *allowDynamicHousekeeping)
74     if err != nil {
75         glog.Fatalf("Failed to create a Container Manager: %s", err)
76     }
77
78     mux := http.DefaultServeMux
79
80     // Register all HTTP handlers.
81     err = cadvisorHttp.RegisterHandlers(mux, containerManager, *httpAuthFile, *httpAuthRealm, *httpDigestFile, *httpDigestRealm)
82     if err != nil {
83         glog.Fatalf("Failed to register HTTP handlers: %v", err)
84     }
85
86     cadvisorHttp.RegisterPrometheusHandler(mux, containerManager, *prometheusEndpoint, nil)
87
88     // Start the manager.
89     if err := containerManager.Start(); err != nil {
90         glog.Fatalf("Failed to start container manager: %v", err)
91     }
... ...

从入口可以得知真正获取 container 和 machine 信息的 interface 为 Manager， github.com/google/cadvisor/manager/manager.go

# github.com/google/cadvisor/manager/manager.go
52 // The Manager interface defines operations for starting a manager and getting
53 // container and machine information.
54 type Manager interface {
55     // Start the manager. Calling other manager methods before this returns
56     // may produce undefined behavior.
57     Start() error
58
59     // Stops the manager.
60     Stop() error
61
62     // Get information about a container.
63     GetContainerInfo(containerName string, query *info.ContainerInfoRequest) (*info.ContainerInfo, error)
... ...

以下对 cadvisor 具体如何获取到 machine 和 docker container 的信息结合代码具体讲解。

# github.com/google/cadvisor/manager/manager.go
158     machineInfo, err := getMachineInfo(sysfs, fsInfo) // 此处通过 getMachineInfo() 函数获取 machine 信息
159     if err != nil {
160         return nil, err
161     }
162     newManager.machineInfo = *machineInfo
163     glog.Infof("Machine: %+v", newManager.machineInfo)

获取 machineinfo 的具体函数 getMachineInfo()

# github.com/google/cadvisor/manager/machine.go
52 func getMachineInfo(sysFs sysfs.SysFs, fsInfo fs.FsInfo) (*info.MachineInfo, error) {
53     cpuinfo, err := ioutil.ReadFile("/proc/cpuinfo")
54     clockSpeed, err := machine.GetClockSpeed(cpuinfo)
55     if err != nil {
56         return nil, err
57     }
58
... ...

MachineInfo 数据结构：

# github.com/google/cadvisor/info/v1/machine.go
131 type MachineInfo struct {
132     // The number of cores in this machine.
133     NumCores int `json:"num_cores"`
134
135     // Maximum clock speed for the cores, in KHz.
136     CpuFrequency uint64 `json:"cpu_frequency_khz"`
137
138     // The amount of memory (in bytes) in this machine
139     MemoryCapacity int64 `json:"memory_capacity"`
140
141     // The machine id
142     MachineID string `json:"machine_id"`
143
144     // The system uuid
145     SystemUUID string `json:"system_uuid"`
146
147     // The boot id
148     BootID string `json:"boot_id"`
149
150     // Filesystems on this machine.
151     Filesystems []FsInfo `json:"filesystems"`
152
153     // Disk map
154     DiskMap map[string]DiskInfo `json:"disk_map"`
155
156     // Network devices
157     NetworkDevices []NetInfo `json:"network_devices"`
158
159     // Machine Topology
160     // Describes cpu/memory layout and hierarchy.
161     Topology []Node `json:"topology"`
162
163     // Cloud provider the machine belongs to.
164     CloudProvider CloudProvider `json:"cloud_provider"`
165
166     // Type of cloud instance (e.g. GCE standard) the machine is.
167     InstanceType InstanceType `json:"instance_type"`
168 }

• cpu /proc/cpuinfo
• mem /proc/meminfo

# github.com/google/cadvisor/utils/machine/machine.go
76 func GetMachineMemoryCapacity() (int64, error) {
77     out, err := ioutil.ReadFile("/proc/meminfo")
78     if err != nil {
79         return 0, err
80     }
81
82     memoryCapacity, err := parseCapacity(out, memoryCapacityRegexp)
83     if err != nil {
84         return 0, err
85     }
86     return memoryCapacity, err
87 }

• machine_id /var/lib/dbus/machine-id
• boot_id /proc/sys/kernel/random/boot_id
• system UUID /sys/class/dmi/id/product_uuid

➜  ~  cat /var/lib/dbus/machine-id
a8919ec7c9ee43bd1bcaf6cd55e1a7bc
➜  ~  cat /proc/sys/kernel/random/boot_id
2f6bac7f-738a-4d85-8b58-53e71296119e
➜  ~  cat /sys/class/dmi/id/product_uuid
F27316D5-4DB3-E411-A26A-F0761C6D26D6
➜  ~

• disk /proc/diskstats

# github.com/google/cadvisor/fs/fs.go
189 func (self *RealFsInfo) GetFsInfoForPath(mountSet map[string]struct{}) ([]Fs, error) {
190     filesystems := make([]Fs, 0)
191     deviceSet := make(map[string]struct{})
192     diskStatsMap, err := getDiskStatsMap("/proc/diskstats") // 磁盘状态通过 /proc/diskstats 获取
193     if err != nil {
194         return nil, err
195     }
... ...

对于分配给容器的 pool 值，如果是 device mapper 类型的，则通过 dmsetup status pool_device_name 获取设备使用情况

# github.com/google/cadvisor/fs/fs.go
... ...
205             case "devicemapper":
206                 total, free, avail, err = getDMStats(device, partition.blockSize)
....

• 获取磁盘设备信息 /sys/block

# github.com/google/cadvisor/utils/sysinfo/sysinfo.go
31 func GetBlockDeviceInfo(sysfs sysfs.SysFs) (map[string]info.DiskInfo, error) {
32     disks, err := sysfs.GetBlockDevices()
       // cadvisor/utils/sysfs/sysfs.go GetBlockDevices() 可知，通过 /sys/block 获取磁盘设备名，其它信息雷同
33     if err != nil {
34         return nil, err
35     }
... ...

➜  ~  cat /sys/block/sda/dev                # 主次设备号
8:0
➜  ~  cat /sys/block/sda/size               # 磁盘设备大小
976773168
➜  ~  cat /sys/block/sda/queue/scheduler    # 磁盘调度类型
noop deadline [cfq]
➜  ~

• netDevices /sys/class/net

# github.com/google/cadvisor/utils/sysinfo/sysinfo.go
87 func GetNetworkDevices(sysfs sysfs.SysFs) ([]info.NetInfo, error) {
88     devs, err := sysfs.GetNetworkDevices()
89     if err != nil {
90         return nil, err
91     }
92     netDevices := []info.NetInfo{}
... ...

➜  ~  cat /sys/class/net/eth0/address
f0:76:1c:6d:26:d6
➜  ~  cat /sys/class/net/eth0/mtu
1500
➜  ~  cat /sys/class/net/eth0/speed
10

# github.com/google/cadvisor/manager/manager.go
201 // Start the container manager.
202 func (self *manager) Start() error {
203     // Register Docker container factory.
204     err := docker.Register(self, self.fsInfo)
205     if err != nil {
206         glog.Errorf("Docker container factory registration failed: %v.", err)
207     }
... ...

cAdvisor 启动 container manager，通过调用 Linux 系统 inotify 监测 cgroup docker 目录的文件变化判断 docker 的创建和删除。

# github.com/google/cadvisor/manager/manager.go
687 func (m *manager) GetProcessList(containerName string, options v2.RequestOptions) ([]v2.ProcessInfo, error) {
688     // override recursive. Only support single container listing.
689     options.Recursive = false
690     conts, err := m.getRequestedContainers(containerName, options)
691     if err != nil {
692         return nil, err
693     }
694     if len(conts) != 1 {
695         return nil, fmt.Errorf("Expected the request to match only one container")
696     }
... ...

# github.com/google/cadvisor/manager/container.go
273         if isRoot || c.info.Name == cgroup {
274             processes = append(processes, v2.ProcessInfo{
275                 User:          fields[0],
276                 Pid:           pid,
277                 Ppid:          ppid,
278                 StartTime:     fields[3],
279                 PercentCpu:    float32(percentCpu),
... ...

# github.com/google/cadvisor manager/manager.go
531 func (self *manager) DockerContainer(containerName string, query *info.ContainerInfoRequest) (info.ContainerInfo, error) {
532     container, err := self.getDockerContainer(containerName)
533     if err != nil {
534         return info.ContainerInfo{}, err
535     }
536
... ...

# github.com/google/cadvisor/manager/container.go
102 func (c *containerData) GetInfo() (*containerInfo, error) {
103     // Get spec and subcontainers.
104     if time.Since(c.lastUpdatedTime) > 5*time.Second {   // 可以看出当上一次更新时间超过 5s 的时候才会更新 info 数据 5
105         err := c.updateSpec()
106         if err != nil {
107             return nil, err
108         }
... ...

# github.com/google/cadvisor/container/docker/handler.go
220 func (self *dockerContainerHandler) GetSpec() (info.ContainerSpec, error) {
221     mi, err := self.machineInfoFactory.GetMachineInfo()
222     if err != nil {
223         return info.ContainerSpec{}, err
224     }

# github.com/google/cadvisor/container/libcontainer/compatibility.go 读取 libcontainer config 文件信息
150 func ReadConfig(dockerRoot, dockerRun, containerID string) (*configs.Config, error) {
151     // Try using the new config if it is available.
152     configPath := configPath(dockerRun, containerID)
153     if utils.FileExists(configPath) {
154         out, err := ioutil.ReadFile(configPath)
155         if err != nil {
156             return nil, err
157         }
158
159         var state libcontainer.State
160         err = json.Unmarshal(out, &state)
161         if err != nil {
162             return nil, err
163         }
164         return &state.Config, nil
165     }

# github.com/google/cadvisor/container/docker/handler.go 磁盘使用率统计目前支持 aufs，这是目前 CentOS7 上没有 filesystem 大小的原因
... ...
232     // For now only enable for aufs filesystems
233     spec.HasFilesystem = self.storageDriver == aufsStorageDriver
... ...
241 func (self *dockerContainerHandler) getFsStats(stats *info.ContainerStats) error {
242     // No support for non-aufs storage drivers.
243     if self.storageDriver != aufsStorageDriver {
244         return nil
245     }
... ...

# github.com/google/cadvisor/container/docker/handler.go
# cgroup 信息是调用 github.com/docker/libcontainer/cgroups 获取
276 func (self *dockerContainerHandler) GetStats() (*info.ContainerStats, error) {
277     stats, err := containerLibcontainer.GetStats(self.cgroupManager, self.rootFs, self.pid)
278     if err != nil {
279         return stats, err
280     }
281     // Clean up stats for containers that don't have their own network - this
282     // includes containers running in Kubernetes pods that use the network of the
283     // infrastructure container. This stops metrics being reported multiple times
284     // for each container in a pod.  如果 container 没有自己的网络，则返回空。对于 K8s pod 内部 container 都是通过 pause container 网络通信
285     if !hasNet(self.networkMode) {
286         stats.Network = info.NetworkStats{}
287     }
288
289     // Get filesystem stats.
290     err = self.getFsStats(stats)
291     if err != nil {
292         return stats, err
293     }
294
295     return stats, nil
296 }

# github.com/google/cadvisor/container/libcontainer/helpers.go
81 // Get cgroup and networking stats of the specified container
82 func GetStats(cgroupManager cgroups.Manager, rootFs string, pid int) (*info.ContainerStats, error) {
83     cgroupStats, err := cgroupManager.GetStats()
84     if err != nil {
85         return nil, err
86     }
87     libcontainerStats := &libcontainer.Stats{
88         CgroupStats: cgroupStats,
89     }
90     stats := toContainerStats(libcontainerStats)
91
92     // If we know the pid then get network stats from /proc/<pid>/net/dev
93     if pid > 0 {
94         netStats, err := networkStatsFromProc(rootFs, pid)
95         if err != nil {
96             glog.V(2).Infof("Unable to get network stats from pid %d: %v", pid, err)
97         } else {
98             stats.Network.Interfaces = append(stats.Network.Interfaces, netStats...)
99         }
... ...

# github.com/docker/libcontainer/cgroups/stats.go
80 type Stats struct {
81     CpuStats    CpuStats    `json:"cpu_stats,omitempty"`
82     MemoryStats MemoryStats `json:"memory_stats,omitempty"`
83     BlkioStats  BlkioStats  `json:"blkio_stats,omitempty"`
84     // the map is in the format "size of hugepage: stats of the hugepage"
85     HugetlbStats map[string]HugetlbStats `json:"hugetlb_stats,omitempty"`
86 }