前言
metric object
package metric
var studentCounterVec = prometheus.NewCounterVec(
prometheus.CounterOpts{
Name: "student",
Help: "The number of student",
},
[]string{"class", "age"},
)
func Start(){
prometheus.MustRegister(studentCounterVec)
http.Handle("/metrics", promhttp.Handler())
go http.ListenAndServe(":8888", nil)
}
func Inc(class, age string) {
studentCounterVec.With(prometheus.Labels{"class": number1, "age": 18}).Inc()
}
之后便可以在代码其它地方 使用metric.Inc 添加某个班级、年龄的学生人数了。
数据写入
一个指标由Metric name + Labels共同确定，若Metric name相同，但Label的值不同，则是不同的Metric。
CounterVec/GaugeVec/HistogramVec/SummaryVec 作为 Counter/Gauge/Histogram/Summary（均实现了Metric interface）的容器，都聚合了 metricVec，以 CounterVec为例，CounterVec.With(labels) ==> CounterVec.GetMetricWith(labels) ==> Metric = metricVec.getMetricWith(labels)
type CounterVec struct {
*metricVec
}
// metricVec is a Collector to bundle metrics of the same name that differ in their label values. metricVec is not used directly (and therefore unexported). It is used as a building block for implementations of vectors of a given metric type, like GaugeVec, CounterVec, SummaryVec, and HistogramVec. It also handles label currying.
// github.com/prometheus/client_golang/prometheus/vec.go
type metricVec struct {
*metricMap
curry []curriedLabelValue
// hashAdd and hashAddByte can be replaced for testing collision handling.
hashAdd func(h uint64, s string) uint64
hashAddByte func(h uint64, b byte) uint64
}
func (v *CounterVec) GetMetricWith(labels Labels) (Counter, error) {
metric, err := v.metricVec.getMetricWith(labels)
if metric != nil {
return metric.(Counter), err
}
return nil, err
}
type metricMap struct {
mtx sync.RWMutex // Protects metrics.
// key=根据label值计算出的hash值
metrics map[uint64][]metricWithLabelValues
desc *Desc
newMetric func(labelValues ...string) Metric
}
type Counter interface {
Metric
Collector
Inc()
Add(float64)
}
数据写入即由开发直接创建 CounterVec/GaugeVec/HistogramVec/SummaryVec ，根据labels 找到对应的metric（ Counter/Gauge/Histogram/Summary） 进行数据操作。
数据读取
可以直接通过 http://ip:port/metrics 获取metric 数据
type Registry struct {
mtx sync.RWMutex
collectorsByID map[uint64]Collector // ID is a hash of the descIDs.
descIDs map[uint64]struct{}
...
}
开发直接创建的 CounterVec/GaugeVec/HistogramVec/SummaryVec 注入到Registry 中，Registry持有一个Collector 集合，同时Counter/Gauge/Histogram/Summary 均实现Collector 接口的 Collect 方法， metric 请求 ==> Registry.Gather() ==> 各种collector.Collect
// Prometheus拉取的入口
http.Handle("/metrics", promhttp.Handler())
// http.go promhttp.Handler()
func Handler() http.Handler {
return InstrumentMetricHandler(
prometheus.DefaultRegisterer, HandlerFor(prometheus.DefaultGatherer, HandlerOpts{}),
)
}
// http.go HandlerFor
func HandlerFor(reg prometheus.Gatherer, opts HandlerOpts) http.Handler {
...
mfs, err := reg.Gather() // 收集Metric信息
...
}
func (r *Registry) Gather() ([]*dto.MetricFamily, error) {
...
// 声明Counter类型的Metric后，需要MustRegist注册到Registry，最终就是保存在collectorsByID里
// Counter类型本身就是一个collector
for _, collector := range r.collectorsByID {
checkedCollectors <- collector
}
...
collectWorker := func() {
for {
select {
case collector := <-checkedCollectors: //collector metric写入checkedMetricChan
collector.Collect(checkedMetricChan) // 执行Counter的Collect，见下文
case collector := <-uncheckedCollectors:
collector.Collect(uncheckedMetricChan)
default:
return
}
wg.Done()
}
}
// 消费 checkedMetricChan 将结果聚合到 []*dto.MetricFamily 中
...
}
func (m *metricMap) Collect(ch chan<- Metric) {
...
for _, metrics := range m.metrics {
for _, metric := range metrics {
ch <- metric.metric
}
}
k8s使用实践
除了开发 手动创建XXVec 并在代码中使用，k8s client-go等一些库 会在代码中定义 XXProvider 接口
k8s.io/client-go
/tools/leaderelection/metrics.go
/util/workqueue/metrics.go
MetricsProvider 作为client-go 与业务开发的边界。
- client-go 并不负责创建 XXVec， XXVec的创建由使用者手动创建，并注册到prometheus registry中，对外通过prometheus server 暴露http api出去。对内通过MetricsProvider 暴露给 client-go workqueue
// k8s.io.component-base.metrics.prometheus.workqueue function init(){ workqueue.SetProvider(workqueueMetricsProvider{}) } -
client-go 通过MetricsProvider 获取到 metric 并赋值数据
// k8s.io/client-go/util/workqueue/metrics.go type MetricsProvider interface { NewDepthMetric(name string) GaugeMetric NewAddsMetric(name string) CounterMetric NewLatencyMetric(name string) HistogramMetric NewWorkDurationMetric(name string) HistogramMetric NewUnfinishedWorkSecondsMetric(name string) SettableGaugeMetric NewLongestRunningProcessorSecondsMetric(name string) SettableGaugeMetric NewRetriesMetric(name string) CounterMetric } type CounterMetric interface { Inc() } // k8s.io/client-go/util/workqueue/queue.go func (q *Type) Add(item interface{}) { ... q.metrics.add(item) ... }