victoriaMetrics无法获取抓取target的问题

victoriaMetrics无法获取抓取target的问题

问题描述

最近在新环境中部署了一个服务，其暴露的指标路径为:10299/metrics，配置文件如下(名称字段有修改)：

apiVersion: v1items:- apiVersion: operator.victoriametrics.com/v1beta1  kind: VMServiceScrape  metadata:    labels:      app_id: audit    name: audit    namespace: default  spec:    endpoints:    - path: /metrics      targetPort: 10299    namespaceSelector:      matchNames:      - default    selector:      matchLabels:        app_id: audit

但在vmagent上查看其状态如下，vmagent无法发现该target：

一般排查方式

1. 确保服务本身没问题，可以通过${podIp}:10299/metrics访问到指标
2. 确保vmservicescrape-->service-->enpoints链路是通的，即配置的selector字段能够正确匹配到对应的资源
3. 确保vmservicescrape格式正确。注：vmservicescrape资源格式不正确可能会导致vmagent无法加载配置，可以通过第5点检测到
4. 确保vmagent中允许发现该命名空间中的target
5. 在vmagent的UI界面执行reload，查看vmagent的日志是否有相关错误提示

经过排查发现上述方式均无法解决问题，更奇怪的是在vmagent的api/v1/targets中无法找到该target，说明vmagent压根没有发现该服务，即vmservicescrape配置没有生效。在vmagent中查看上述vmservicescrape生成的配置文件如下(其拼接了静态配置)，可以看到它使用了kubernetes_sd_configs的方式来发现target：

- job_name: serviceScrape/default/audit/0  metrics_path: /metrics  relabel_configs:  - source_labels: [__meta_kubernetes_service_label_app_id]    regex: audit    action: keep  - source_labels: [__meta_kubernetes_pod_container_port_number]    regex: "10299"    action: keep  - source_labels: [__meta_kubernetes_endpoint_address_target_kind, __meta_kubernetes_endpoint_address_target_name]    separator: ;    target_label: node    regex: Node;(.*)    replacement: ${1}  - source_labels: [__meta_kubernetes_endpoint_address_target_kind, __meta_kubernetes_endpoint_address_target_name]    separator: ;    target_label: pod    regex: Pod;(.*)    replacement: ${1}  - source_labels: [__meta_kubernetes_pod_name]    target_label: pod  - source_labels: [__meta_kubernetes_pod_container_name]    target_label: container  - source_labels: [__meta_kubernetes_namespace]    target_label: namespace  - source_labels: [__meta_kubernetes_service_name]    target_label: service  - source_labels: [__meta_kubernetes_service_name]    target_label: job    replacement: ${1}  - target_label: endpoint    replacement: "8080"  kubernetes_sd_configs:  - role: endpoints    namespaces:      own_namespace: false      names:      - default

代码分析

既然配置没有问题，那只能通过victoriametrics的kubernetes_sd_configs的运作方式看下到底是哪里出问题了。在victoriametrics的源码可以看到其拼接的target url如下：

scrapeURL := fmt.Sprintf("%s://%s%s%s%s", schemeRelabeled, addressRelabeled, metricsPathRelabeled, optionalQuestion, paramsStr)

其中：

• schemeRelabeled：默认是http
• metricsPathRelabeled：即生成的配置文件的metrics_path字段
• optionalQuestion和paramsStr没有配置，可以忽略

最主要的字段就是addressRelabeled，它来自一个名为"__address__"的标签

func mergeLabels(swc *scrapeWorkConfig, target string, extraLabels, metaLabels map[string]string) []prompbmarshal.Label {	...	m["job"] = swc.jobName	m["__address__"] = target	m["__scheme__"] = swc.scheme	m["__metrics_path__"] = swc.metricsPath	m["__scrape_interval__"] = swc.scrapeInterval.String()	m["__scrape_timeout__"] = swc.scrapeTimeout.String()	...}

继续跟踪代码，可以看到该标签是通过sc.KubernetesSDConfigs[i].MustStart获取到的，从KubernetesSDConfigs的名称上看，它就是负责处理kubernetes_sd_configs机制的：

func (sc *ScrapeConfig) mustStart(baseDir string) {	swosFunc := func(metaLabels map[string]string) interface{} {		target := metaLabels["__address__"]		sw, err := sc.swc.getScrapeWork(target, nil, metaLabels)		if err != nil {			logger.Errorf("cannot create kubernetes_sd_config target %q for job_name %q: %s", target, sc.swc.jobName, err)			return nil		}		return sw	}	for i := range sc.KubernetesSDConfigs {		sc.KubernetesSDConfigs[i].MustStart(baseDir, swosFunc)	}}

继续往下看，看看这个"__address__"字段到底是什么，函数调用如下：

MustStart --> cfg.aw.mustStart --> aw.gw.startWatchersForRole --> uw.reloadScrapeWorksForAPIWatchersLocked --> o.getTargetLabels

最后一个函数getTargetLabels是个接口方法：

type object interface {	key() string	// getTargetLabels must be called under gw.mu lock.	getTargetLabels(gw *groupWatcher) []map[string]string}

getTargetLabels的实现如下，这就是kubernetes_sd_configs的各个role的具体实现。上述服务用到的是kubernetes_sd_configsrole为endpoints：

其实现如下：

func (eps *Endpoints) getTargetLabels(gw *groupWatcher) []map[string]string {	var svc *Service	if o := gw.getObjectByRoleLocked("service", eps.Metadata.Namespace, eps.Metadata.Name); o != nil {		svc = o.(*Service)	}	podPortsSeen := make(map[*Pod][]int)	var ms []map[string]string	for _, ess := range eps.Subsets {		for _, epp := range ess.Ports {			ms = appendEndpointLabelsForAddresses(ms, gw, podPortsSeen, eps, ess.Addresses, epp, svc, "true")			ms = appendEndpointLabelsForAddresses(ms, gw, podPortsSeen, eps, ess.NotReadyAddresses, epp, svc, "false")		}	}	// See https://kubernetes.io/docs/reference/labels-annotations-taints/#endpoints-kubernetes-io-over-capacity	// and https://github.com/kubernetes/kubernetes/pull/99975	switch eps.Metadata.Annotations.GetByName("endpoints.kubernetes.io/over-capacity") {	case "truncated":		logger.Warnf(`the number of targets for "role: endpoints" %q exceeds 1000 and has been truncated; please use "role: endpointslice" instead`, eps.Metadata.key())	case "warning":		logger.Warnf(`the number of targets for "role: endpoints" %q exceeds 1000 and will be truncated in the next k8s releases; please use "role: endpointslice" instead`, eps.Metadata.key())	}	// Append labels for skipped ports on seen pods.	portSeen := func(port int, ports []int) bool {		for _, p := range ports {			if p == port {				return true			}		}		return false	}	for p, ports := range podPortsSeen {		for _, c := range p.Spec.Containers {			for _, cp := range c.Ports {				if portSeen(cp.ContainerPort, ports) {					continue				}				addr := discoveryutils.JoinHostPort(p.Status.PodIP, cp.ContainerPort)				m := map[string]string{					"__address__": addr,				}				p.appendCommonLabels(m)				p.appendContainerLabels(m, c, &cp)				if svc != nil {					svc.appendCommonLabels(m)				}				ms = append(ms, m)			}		}	}	return ms}

可以看到，"__address__"其实就是拼接了p.Status.PodIP和cp.ContainerPort，而p则代表一个kubernetes的pod数据结构，因此要求：

1. pod状态是running的，且能够正确分配到PodIP
2. p.Spec.Containers[].ports[].ContainerPort中配置了暴露metrics target的端口

问题解决

鉴于上述分析，查看了一下环境中的deployment，发现该deployment只配置了8080端口，并没有配置暴露指标的端口10299。问题解决。

apiVersion: apps/v1kind: Deploymentmetadata:  labels:    app_id: audit  name: audit  namespace: defaultspec:  ...  template:    metadata:      ...    spec:      containers:      - env:        - name: APP_ID          value: audit        ports:        - containerPort: 8080          protocol: TCP

总结

kubernetes_sd_configs方式其实就是通过listwatch的方式获取对应role的配置，然后拼接出target的__address__，此外它还会暴露一些额外的指标，如：

• __meta_kubernetes_endpoint_hostname: Hostname of the endpoint.
• __meta_kubernetes_endpoint_node_name: Name of the node hosting the endpoint.
• __meta_kubernetes_endpoint_ready: Set to true or false for the endpoint's ready state.
• __meta_kubernetes_endpoint_port_name: Name of the endpoint port.
• __meta_kubernetes_endpoint_port_protocol: Protocol of the endpoint port.
• __meta_kubernetes_endpoint_address_target_kind: Kind of the endpoint address target.
• __meta_kubernetes_endpoint_address_target_name: Name of the endpoint address target.