Prometheus源码系列： 启动过程分析

Prometheus 启动过程中，主要包含服务组件初始化，服务组件配置应用及启动各个服务组件三个部分，下面基于版本 v2.7.1，详细分析这三部分内容

１．服务组件初始化

(1) Storage组件初始化

　　Prometheus的Storage组件是时序数据库，包含两个：localStorage和remoteStorage．localStorage当前版本指TSDB，用于对metrics的本地存储存储，remoteStorage用于metrics的远程存储，其中fanoutStorage作为localStorage和remoteStorage的读写代理服务器．初始化流程如下

prometheus/cmd/prometheus/main.go

localStorage  = &tsdb.ReadyStorage{} //本地存储
remoteStorage = remote.NewStorage(log.With(logger, "component", "remote"), //远端存储 localStorage.StartTime, time.Duration(cfg.RemoteFlushDeadline))
fanoutStorage = storage.NewFanout(logger, localStorage, remoteStorage) //读写代理服务器

(2) notifier 组件初始化

 　　notifier组件用于发送告警信息给AlertManager，通过方法notifier.NewManager完成初始化

prometheus/cmd/prometheus/main.go

notifierManager = notifier.NewManager(&cfg.notifier, log.With(logger, "component", "notifier"))

(3) discoveryManagerScrape组件初始化

　　discoveryManagerScrape组件用于服务发现，当前版本支持多种服务发现系统，比如kuberneters等，通过方法discovery.NewManager完成初始化，

prometheus/cmd/prometheus/main.go

discoveryManagerScrape  = discovery.NewManager(ctxScrape, log.With(logger, "component", "discovery manager scrape"), discovery.Name("scrape"))

(4) discoveryManagerNotify组件初始化

 　　discoveryManagerNotify组件用于告警通知服务发现，比如AlertManager服务．也是通过方法discovery.NewManager完成初始化，不同的是，discoveryManagerNotify服务于notify，而discoveryManagerScrape服务与scrape

prometheus/cmd/prometheus/main.go

discoveryManagerNotify  = discovery.NewManager(ctxNotify, log.With(logger, "component", "discovery manager notify"), discovery.Name("notify")

(5) scrapeManager组件初始化

 　　scrapeManager组件利用discoveryManagerScrape组件发现的targets，抓取对应targets的所有metrics，并将抓取的metrics存储到fanoutStorage中，通过方法scrape.NewManager完成初始化

prometheus/cmd/prometheus/main.go

scrapeManager = scrape.NewManager(log.With(logger, "component", "scrape manager"), fanoutStorage)

(6) queryEngine组件

　　queryEngine组件用于rules查询和计算，通过方法promql.NewEngine完成初始化

prometheus/cmd/prometheus/main.go

opts =