【prometheus】-03 轻松搞定Prometheus文件服务发现
【prometheus】-02 一张图彻底搞懂Prometheus服务发现机制
Prometheus服务发现机制之Eureka
概述
Eureka服务发现协议允许使用Eureka Rest API检索出Prometheus需要监控的targets，Prometheus会定时周期性的从Eureka调用Eureka Rest API，并将每个应用实例创建出一个target。
Eureka服务发现协议支持对如下元标签进行relabeling：
__meta_eureka_app_name: the name of the app__meta_eureka_app_instance_id: the ID of the app instance__meta_eureka_app_instance_hostname: the hostname of the instance__meta_eureka_app_instance_homepage_url: the homepage url of the app instance__meta_eureka_app_instance_statuspage_url: the status page url of the app instance__meta_eureka_app_instance_healthcheck_url: the health check url of the app instance__meta_eureka_app_instance_ip_addr: the IP address of the app instance__meta_eureka_app_instance_vip_address: the VIP address of the app instance__meta_eureka_app_instance_secure_vip_address: the secure VIP address of the app instance__meta_eureka_app_instance_status: the status of the app instance__meta_eureka_app_instance_port: the port of the app instance__meta_eureka_app_instance_port_enabled: the port enabled of the app instance__meta_eureka_app_instance_secure_port: the secure port address of the app instance__meta_eureka_app_instance_secure_port_enabled: the secure port of the app instance__meta_eureka_app_instance_country_id: the country ID of the app instance__meta_eureka_app_instance_metadata_<metadataname>: app instance metadata__meta_eureka_app_instance_datacenterinfo_name: the datacenter name of the app instance__meta_eureka_app_instance_datacenterinfo_<metadataname>: the datacenter metadata
eureka_sd_configs配置可选项如下：
# The URL to connect to the Eureka server.
server: <string>
# Sets the `Authorization` header on every request with the
# configured username and password.
# password and password_file are mutually exclusive.
basic_auth:
[ username: <string> ]
[ password: <secret> ]
[ password_file: <string> ]
# Optional `Authorization` header configuration.
authorization:
# Sets the authentication type.
[ type: <string> | default: Bearer ]
# Sets the credentials. It is mutually exclusive with
# `credentials_file`.
[ credentials: <secret> ]
# Sets the credentials to the credentials read from the configured file.
# It is mutually exclusive with `credentials`.
[ credentials_file: <filename> ]
# Optional OAuth 2.0 configuration.
# Cannot be used at the same time as basic_auth or authorization.
oauth2:
[ <oauth2> ]
# 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 ]
协议分析
通过前面分析的Prometheus服务发现原理以及基于文件方式服务发现协议实现的分析，Eureka服务发现大致原理如下图：
通过解析配置中eureka_sd_configs协议的job生成Config，然后NewDiscovery方法创建出对应的Discoverer，最后调用Discoverer.Run()方法启动服务发现targets。
1、基于文件服务发现配置解析
假如我们定义如下job:
- job_name: 'eureka'
eureka_sd_configs:
- server: http://localhost:8761/eureka
会被解析成eureka.SDConfig如下：
eureka.SDConfig定义如下：
type SDConfig struct {
// eureka-server地址
Server string `yaml:"server,omitempty"`
// http请求client配置，如:认证信息
HTTPClientConfig config.HTTPClientConfig `yaml:",inline"`
// 周期刷新间隔，默认30s
RefreshInterval model.Duration `yaml:"refresh_interval,omitempty"`
}
2、Discovery创建
func NewDiscovery(conf *SDConfig, logger log.Logger) (*Discovery, error) {
rt, err := config.NewRoundTripperFromConfig(conf.HTTPClientConfig, "eureka_sd", config.WithHTTP2Disabled())
if err != nil {
return nil, err
}
d := &Discovery{
client: &http.Client{Transport: rt},
server: conf.Server,
}
d.Discovery = refresh.NewDiscovery(
logger,
"eureka",
time.Duration(conf.RefreshInterval),
d.refresh,
)
return d, nil
}
3、Discovery创建完成，最后会调用Discovery.Run()启动服务发现：
和上一节分析的服务发现之File机制类似，执行Run方法时会执行tgs, err := d.refresh(ctx)，然后创建定时周期触发器，不停执行tgs, err := d.refresh(ctx)，将返回的targets结果信息通过channel传递出去。
4、上面Run方法核心是调用d.refresh(ctx)逻辑获取targets，基于Eureka发现协议主要实现逻辑就在这里：
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)
//假如到
tg.Targets = append(tg.Targets, targets...)
}
return []*targetgroup.Group{tg}, nil
}
refresh方法主要有两个流程：
1、fetchApps()：从eureka-server的/eureka/apps接口拉取注册服务信息；
2、targetsForApp()：遍历app下instance，将每个instance解析出一个target，并添加一堆元标签数据。
如下就是从eureka-server的/eureka/apps接口拉取的注册服务信息：
<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>
5、instance信息解析target：
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
}
解析比较简单，就不再分析，解析后的标签数据如下图：
标签中有两个特别说明下：
1、__address__：这个取值instance.hostname和port(默认80)，所以要注意注册到eureka上的hostname准确性，不然可能无法抓取；
2、metadata-map数据会被转成__meta_eureka_app_instance_metadata_<metadataname>格式标签，prometheus进行relabeling 一般操作metadata-map，可以自定义metric_path、抓取端口等；
3、prometheus的label只支持[a-zA-Z0-9_]，其它非法字符都会被转换成下划线，具体参加：strutil.SanitizeLabelName(m.XMLName.Local)；但是eureka的metadata-map标签含有下划线时，注册到eureka-server上变成双下划线，如下配置:
eureka:
instance:
metadata-map:
scrape_enable: true
scrape.port: 8080
通过/eureka/apps获取如下：
总结
基于Eureka方式的服务原理如下图：
大概说明：Discoverer启动后定时周期触发从eureka server的/eureka/apps接口拉取注册服务元数据，然后通过targetsForApp遍历app下的instance，将每个instance解析成target，并将其它元数据信息转换成target原标签可以用于target抓取前relabeling操作。
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