【云原生 • Prometheus】Prometheus 注册中心Eureka服务发现原理

- job_name: 'eureka'
  eureka_sd_configs:
    - server: http://localhost:8761/eureka #eureka server地址
      refresh_interval: 1m #刷新间隔，默认30s

server: <string>

basic_auth:
  [ username: <string> ]
  [ password: <secret> ]
  [ password_file: <string> ]

# Configures the scrape request's TLS settings.
tls_config:
  [ <tls_config> ]

# Optional proxy URL.
[ proxy_url: <string> ]

# Configure whether HTTP requests follow HTTP 3xx redirects.
[ follow_redirects: <bool> | default = true ]

# Refresh interval to re-read the app instance list.
[ refresh_interval: <duration> | default = 30s ]

func (d *Discovery) refresh(ctx context.Context) ([]*targetgroup.Group, error) {
 // 通过Eureka REST API接口从eureka拉取元数据：http://ip:port/eureka/apps
 apps, err := fetchApps(ctx, d.server, d.client)
 if err != nil {
  return nil, err
 }

 tg := &targetgroup.Group{
  Source: "eureka",
 }

 for _, app := range apps.Applications {//遍历app
        // targetsForApp()方法将app下每个instance部分转成target
  targets := targetsForApp(&app)
        //解析的采集点合入一起
  tg.Targets = append(tg.Targets, targets...)
 }
 return []*targetgroup.Group{tg}, nil
}

<applications>
    <versions__delta>1</versions__delta>
    <apps__hashcode>UP_1_</apps__hashcode>
    <application>
        <name>SERVICE-PROVIDER-01</name>
        <instance>
            <instanceId>localhost:service-provider-01:8001</instanceId>
            <hostName>192.168.3.121</hostName>
            <app>SERVICE-PROVIDER-01</app>
            <ipAddr>192.168.3.121</ipAddr>
            <status>UP</status>
            <overriddenstatus>UNKNOWN</overriddenstatus>
            <port enabled="true">8001</port>
            <securePort enabled="false">443</securePort>
            <countryId>1</countryId>
            <dataCenterInfo class="com.netflix.appinfo.InstanceInfo$DefaultDataCenterInfo">
                <name>MyOwn</name>
            </dataCenterInfo>
            <leaseInfo>
                <renewalIntervalInSecs>30</renewalIntervalInSecs>
                <durationInSecs>90</durationInSecs>
                <registrationTimestamp>1629385562130</registrationTimestamp>
                <lastRenewalTimestamp>1629385682050</lastRenewalTimestamp>
                <evictionTimestamp>0</evictionTimestamp>
                <serviceUpTimestamp>1629385562132</serviceUpTimestamp>
            </leaseInfo>
            <metadata>
                <management.port>8001</management.port>
                <scrape__enable>true</scrape__enable>
                <scrape.port>8080</scrape.port>
            </metadata>
            <homePageUrl>http://192.168.3.121:8001/</homePageUrl>
            <statusPageUrl>http://192.168.3.121:8001/actuator/info</statusPageUrl>
            <healthCheckUrl>http://192.168.3.121:8001/actuator/health</healthCheckUrl>
            <vipAddress>service-provider-01</vipAddress>
            <secureVipAddress>service-provider-01</secureVipAddress>
            <isCoordinatingDiscoveryServer>false</isCoordinatingDiscoveryServer>
            <lastUpdatedTimestamp>1629385562132</lastUpdatedTimestamp>
            <lastDirtyTimestamp>1629385562039</lastDirtyTimestamp>
            <actionType>ADDED</actionType>
        </instance>
    </application>
</applications>

func targetsForApp(app *Application) []model.LabelSet {
 targets := make([]model.LabelSet, 0, len(app.Instances))

 // Gather info about the app's 'instances'. Each instance is considered a task.
 for _, t := range app.Instances {
  var targetAddress string
        // __address__取值方式：instance.hostname和port，没有port则默认port=80
  if t.Port != nil {
   targetAddress = net.JoinHostPort(t.HostName, strconv.Itoa(t.Port.Port))
  } else {
   targetAddress = net.JoinHostPort(t.HostName, "80")
  }

  target := model.LabelSet{
   model.AddressLabel:  lv(targetAddress),
   model.InstanceLabel: lv(t.InstanceID),

   appNameLabel:                     lv(app.Name),
   appInstanceHostNameLabel:         lv(t.HostName),
   appInstanceHomePageURLLabel:      lv(t.HomePageURL),
   appInstanceStatusPageURLLabel:    lv(t.StatusPageURL),
   appInstanceHealthCheckURLLabel:   lv(t.HealthCheckURL),
   appInstanceIPAddrLabel:           lv(t.IPAddr),
   appInstanceVipAddressLabel:       lv(t.VipAddress),
   appInstanceSecureVipAddressLabel: lv(t.SecureVipAddress),
   appInstanceStatusLabel:           lv(t.Status),
   appInstanceCountryIDLabel:        lv(strconv.Itoa(t.CountryID)),
   appInstanceIDLabel:               lv(t.InstanceID),
  }

  if t.Port != nil {
   target[appInstancePortLabel] = lv(strconv.Itoa(t.Port.Port))
   target[appInstancePortEnabledLabel] = lv(strconv.FormatBool(t.Port.Enabled))
  }

  if t.SecurePort != nil {
   target[appInstanceSecurePortLabel] = lv(strconv.Itoa(t.SecurePort.Port))
   target[appInstanceSecurePortEnabledLabel] = lv(strconv.FormatBool(t.SecurePort.Enabled))
  }

  if t.DataCenterInfo != nil {
   target[appInstanceDataCenterInfoNameLabel] = lv(t.DataCenterInfo.Name)

   if t.DataCenterInfo.Metadata != nil {
    for _, m := range t.DataCenterInfo.Metadata.Items {
     ln := strutil.SanitizeLabelName(m.XMLName.Local)
     target[model.LabelName(appInstanceDataCenterInfoMetadataPrefix+ln)] = lv(m.Content)
    }
   }
  }

  if t.Metadata != nil {
   for _, m := range t.Metadata.Items {
                // prometheus label只支持[^a-zA-Z0-9_]字符，其它非法字符都会被替换成下划线_
    ln := strutil.SanitizeLabelName(m.XMLName.Local)
    target[model.LabelName(appInstanceMetadataPrefix+ln)] = lv(m.Content)
   }
  }

  targets = append(targets, target)

 }
 return targets
}

eureka:
  instance:
    metadata-map:
      scrape_enable: true
      scrape.port: 8080