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本篇内容讲解

• 采集段静态配置的解释
• static_configs解析相关源码

采集段解释

采集段是以job为单位配置的，服务器中查看prometheus配置如下：

# 采集配置段
scrape_configs:# The job name is added as a label `job=<job_name>` to any timeseries scraped from this config.- job_name: "prometheus"# metrics_path defaults to '/metrics'# scheme defaults to 'http'.static_configs:- targets: ["localhost:9090"]

target页面查看此job:
在页面上观察配置文件可以看到补全信息,如下：

- job_name: prometheus# true代表使用原始数据的时间戳，false代表使用prometheus采集器的时间戳honor_timestamps: true# 多久执行一次采集，就是这个job 多久执行一次scrape_interval: 15s# 采集的超时scrape_timeout: 15s# 就是采集target的 metric暴露 http path，默认是/metrics ,比如探针型的就是/probemetrics_path: /metrics# 采集目标的协议 是否是httpsscheme: http# 是否跟踪 redirect follow_redirects: truestatic_configs:- targets:- localhost:9090

查看源码，在prometheus/config/config.go可以看到全量的配置项：

type ScrapeConfig struct {// The job name to which the job label is set by default.JobName string `yaml:"job_name"`// Indicator whether the scraped metrics should remain unmodified.HonorLabels bool `yaml:"honor_labels,omitempty"`// Indicator whether the scraped timestamps should be respected.HonorTimestamps bool `yaml:"honor_timestamps"`// A set of query parameters with which the target is scraped.Params url.Values `yaml:"params,omitempty"`// How frequently to scrape the targets of this scrape config.ScrapeInterval model.Duration `yaml:"scrape_interval,omitempty"`// The timeout for scraping targets of this config.ScrapeTimeout model.Duration `yaml:"scrape_timeout,omitempty"`// The HTTP resource path on which to fetch metrics from targets.MetricsPath string `yaml:"metrics_path,omitempty"`// The URL scheme with which to fetch metrics from targets.Scheme string `yaml:"scheme,omitempty"`// An uncompressed response body larger than this many bytes will cause the// scrape to fail. 0 means no limit.BodySizeLimit units.Base2Bytes `yaml:"body_size_limit,omitempty"`// More than this many samples post metric-relabeling will cause the scrape to// fail.SampleLimit uint `yaml:"sample_limit,omitempty"`// More than this many targets after the target relabeling will cause the// scrapes to fail.TargetLimit uint `yaml:"target_limit,omitempty"`// More than this many labels post metric-relabeling will cause the scrape to// fail.LabelLimit uint `yaml:"label_limit,omitempty"`// More than this label name length post metric-relabeling will cause the// scrape to fail.LabelNameLengthLimit uint `yaml:"label_name_length_limit,omitempty"`// More than this label value length post metric-relabeling will cause the// scrape to fail.LabelValueLengthLimit uint `yaml:"label_value_length_limit,omitempty"`// We cannot do proper Go type embedding below as the parser will then parse// values arbitrarily into the overflow maps of further-down types.ServiceDiscoveryConfigs discovery.Configs       `yaml:"-"`HTTPClientConfig        config.HTTPClientConfig `yaml:",inline"`// List of target relabel configurations.RelabelConfigs []*relabel.Config `yaml:"relabel_configs,omitempty"`// List of metric relabel configurations.MetricRelabelConfigs []*relabel.Config `yaml:"metric_relabel_configs,omitempty"`
}

疑问： 为何在上述ScrapeConfig配置段中没有找到 static_configs配置项？
继续查找源码，在prometheus/discovery/registry.go中找到，

configFields = append(configFields, reflect.StructField{}) // Add empty field at end.copy(configFields[i+1:], configFields[i:])                 // Shift fields to the right.configFields[i] = reflect.StructField{                     // Write new field in place.Name: fieldName,Type: reflect.SliceOf(elemType),Tag:  reflect.StructTag(`yaml:"` + yamlKey + `,omitempty"`),}

看到这里 在registry.go中 的init 函数会在包自动导入的时候注册static_configs 到configFields中，所有服务发现都会在各自包中的init方法自动注册自己。
追查 configFields是干什么用的？
prometheus\config\config.go文件中，ScrapeConfig实现了 yaml的Unmarshaler接口 中的UnmarshalYAML方法，所以在yaml解析的时候 ScrapeConfig字段时会调用这个UnmarshalYAML方法。

func (c *ScrapeConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {*c = DefaultScrapeConfigif err := discovery.UnmarshalYAMLWithInlineConfigs(c, unmarshal); err != nil {return err}

UnmarshalYAMLWithInlineConfigs中 调用 getConfigType，getConfigType方法中操作了configFields结构体。
总结：

• ScrapeConfig使用指定的UnmarshalYAML方法
• 当中会去判断采用的是静态配置还是 服务发现的
• 这样写的好处是不需要通过if-else判断，而且每种服务发现的配置是不一样的