148 lines
5.9 KiB
Markdown
148 lines
5.9 KiB
Markdown
# 监控
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在前面的[安装heapster插件](heapster-addon-installation.md)章节，我们已经谈到Kubernetes本身提供了监控插件作为集群和容器监控的选择，但是在实际使用中，因为种种原因，再考虑到跟我们自身的监控系统集成，我们准备重新造轮子。
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## 容器的命名规则
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首先我们需要清楚使用cAdvisor收集的数据的格式和字段信息。
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当我们通过cAdvisor获取到了容器的信息后，例如访问`${NODE_IP}:4194/api/v1.3/docker`获取的json结果中的某个容器包含如下字段：
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```json
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"labels": {
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"annotation.io.kubernetes.container.hash": "f47f0602",
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"annotation.io.kubernetes.container.ports": "[{\"containerPort\":80,\"protocol\":\"TCP\"}]",
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"annotation.io.kubernetes.container.restartCount": "0",
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"annotation.io.kubernetes.container.terminationMessagePath": "/dev/termination-log",
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"annotation.io.kubernetes.container.terminationMessagePolicy": "File",
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"annotation.io.kubernetes.pod.terminationGracePeriod": "30",
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"io.kubernetes.container.logpath": "/var/log/pods/d8a2e995-3617-11e7-a4b0-ecf4bbe5d414/php-redis_0.log",
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"io.kubernetes.container.name": "php-redis",
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"io.kubernetes.docker.type": "container",
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"io.kubernetes.pod.name": "frontend-2337258262-771lz",
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"io.kubernetes.pod.namespace": "default",
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"io.kubernetes.pod.uid": "d8a2e995-3617-11e7-a4b0-ecf4bbe5d414",
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"io.kubernetes.sandbox.id": "843a0f018c0cef2a5451434713ea3f409f0debc2101d2264227e814ca0745677"
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},
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```
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这些信息其实都是kubernetes创建容器时给docker container打的`Labels`，使用`docker inspect $conainer_name`命令同样可以看到上述信息。
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你是否想过这些label跟容器的名字有什么关系？当你在node节点上执行`docker ps`看到的容器名字又对应哪个应用的Pod呢？
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在kubernetes代码中pkg/kubelet/dockertools/docker.go中的BuildDockerName方法定义了容器的名称规范。
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这段容器名称定义代码如下：
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```go
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// Creates a name which can be reversed to identify both full pod name and container name.
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// This function returns stable name, unique name and a unique id.
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// Although rand.Uint32() is not really unique, but it's enough for us because error will
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// only occur when instances of the same container in the same pod have the same UID. The
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// chance is really slim.
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func BuildDockerName(dockerName KubeletContainerName, container *v1.Container) (string, string, string) {
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containerName := dockerName.ContainerName + "." + strconv.FormatUint(kubecontainer.HashContainerLegacy(container), 16)
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stableName := fmt.Sprintf("%s_%s_%s_%s",
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containerNamePrefix,
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containerName,
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dockerName.PodFullName,
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dockerName.PodUID)
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UID := fmt.Sprintf("%08x", rand.Uint32())
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return stableName, fmt.Sprintf("%s_%s", stableName, UID), UID
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}
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// Unpacks a container name, returning the pod full name and container name we would have used to
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// construct the docker name. If we are unable to parse the name, an error is returned.
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func ParseDockerName(name string) (dockerName *KubeletContainerName, hash uint64, err error) {
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// For some reason docker appears to be appending '/' to names.
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// If it's there, strip it.
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name = strings.TrimPrefix(name, "/")
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parts := strings.Split(name, "_")
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if len(parts) == 0 || parts[0] != containerNamePrefix {
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err = fmt.Errorf("failed to parse Docker container name %q into parts", name)
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return nil, 0, err
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}
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if len(parts) < 6 {
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// We have at least 5 fields. We may have more in the future.
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// Anything with less fields than this is not something we can
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// manage.
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glog.Warningf("found a container with the %q prefix, but too few fields (%d): %q", containerNamePrefix, len(parts), name)
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err = fmt.Errorf("Docker container name %q has less parts than expected %v", name, parts)
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return nil, 0, err
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}
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nameParts := strings.Split(parts[1], ".")
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containerName := nameParts[0]
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if len(nameParts) > 1 {
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hash, err = strconv.ParseUint(nameParts[1], 16, 32)
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if err != nil {
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glog.Warningf("invalid container hash %q in container %q", nameParts[1], name)
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}
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}
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podFullName := parts[2] + "_" + parts[3]
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podUID := types.UID(parts[4])
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return &KubeletContainerName{podFullName, podUID, containerName}, hash, nil
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}
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```
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我们可以看到容器名称中包含如下几个字段，中间用下划线隔开，至少有6个字段，未来可能添加更多字段。
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下面的是四个基本字段。
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```
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containerNamePrefix_containerName_PodFullName_PodUID
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```
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所有kubernetes启动的容器的containerNamePrefix都是k8s。
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Kubernetes启动的docker容器的容器名称规范，下面以官方示例guestbook为例，Deployment 名为 frontend中启动的名为php-redis的docker容器的副本书为3。
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Deployment frontend的配置如下：
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```yaml
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apiVersion: extensions/v1beta1
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kind: Deployment
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metadata:
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name: frontend
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spec:
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template:
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metadata:
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labels:
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app: guestbook
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tier: frontend
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spec:
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containers:
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- name: php-redis
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image: bj-xg-oam-docker-hub-001.tendcloud.com/library/gb-frontend:v4
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resources:
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requests:
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cpu: 100m
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memory: 100Mi
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env:
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- name: GET_HOSTS_FROM
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value: dns
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ports:
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- containerPort: 80
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```
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我们选取三个实例中的一个运行php-redis的docker容器。
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```
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k8s_php-redis_frontend-2337258262-154p7_default_d8a2e2dd-3617-11e7-a4b0-ecf4bbe5d414_0
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```
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- containerNamePrefix：k8s
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- containerName：php-redis
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- podFullName：frontend-2337258262-154p7
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- computeHash：154p7
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- deploymentName：frontend
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- replicaSetName：frontend-2337258262
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- namespace：default
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- podUID：d8a2e2dd-3617-11e7-a4b0-ecf4bbe5d414
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kubernetes容器命名规则解析，见下图所示。
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