解析文件中的prometheus指标并更新计数器

Question

我有一个由批处理定期运行的go应用程序。每次运行时，它应该从文件中读取一些prometheus指标，运行其逻辑，更新成功/失败计数器，并将指标写回文件。

通过查看How to parse Prometheus data和godocs for prometheus，我能够读入文件，但我不知道如何使用expfmt.ExtractSamples()返回的值更新app_processed_total。

这就是我到目前为止所做的。有人能告诉我我该怎么做吗？如何将获取的向量类型转换为CounterVec

package main

import (
    "fmt"
    "net/http"
    "strings"
    "time"

    "github.com/prometheus/client_golang/prometheus"
    "github.com/prometheus/client_golang/prometheus/promhttp"
    dto "github.com/prometheus/client_model/go"
    "github.com/prometheus/common/expfmt"
    "github.com/prometheus/common/model"
)

var (
    fileOnDisk     = prometheus.NewRegistry()
    processedTotal = prometheus.NewCounterVec(prometheus.CounterOpts{
        Name: "app_processed_total",
        Help: "Number of times ran",
    }, []string{"status"})
)

func doInit() {
    prometheus.MustRegister(processedTotal)
}

func recordMetrics() {
    go func() {
        for {
            processedTotal.With(prometheus.Labels{"status": "ok"}).Inc()
            time.Sleep(5 * time.Second)
        }
    }()
}

func readExistingMetrics() {
    var parser expfmt.TextParser
    text := `
# HELP app_processed_total Number of times ran
# TYPE app_processed_total counter
app_processed_total{status="ok"} 300
`
    parseText := func() ([]*dto.MetricFamily, error) {
        parsed, err := parser.TextToMetricFamilies(strings.NewReader(text))
        if err != nil {
            return nil, err
        }
        var result []*dto.MetricFamily
        for _, mf := range parsed {
            result = append(result, mf)

        }
        return result, nil
    }

    gatherers := prometheus.Gatherers{
        fileOnDisk,
        prometheus.GathererFunc(parseText),
    }

    gathering, err := gatherers.Gather()
    if err != nil {
        fmt.Println(err)
    }

    fmt.Println("gathering: ", gathering)
    for _, g := range gathering {
        vector, err := expfmt.ExtractSamples(&expfmt.DecodeOptions{
            Timestamp: model.Now(),
        }, g)

        fmt.Println("vector: ", vector)
        if err != nil {
            fmt.Println(err)
        }

        // How can I update processedTotal with this new value?
    }

}

func main() {
    doInit()
    readExistingMetrics()
    recordMetrics()

    http.Handle("/metrics", promhttp.Handler())
    http.ListenAndServe("localhost:2112", nil)
}

Answer 1

我相信你需要使用processedTotal.WithLabelValues("ok").Inc()或者类似的东西。

更完整的例子在这里

func ExampleCounterVec() {
    httpReqs := prometheus.NewCounterVec(
        prometheus.CounterOpts{
            Name: "http_requests_total",
            Help: "How many HTTP requests processed, partitioned by status code and HTTP method.",
        },
        []string{"code", "method"},
    )
    prometheus.MustRegister(httpReqs)

    httpReqs.WithLabelValues("404", "POST").Add(42)

    // If you have to access the same set of labels very frequently, it
    // might be good to retrieve the metric only once and keep a handle to
    // it. But beware of deletion of that metric, see below!
    m := httpReqs.WithLabelValues("200", "GET")
    for i := 0; i < 1000000; i++ {
        m.Inc()
    }
    // Delete a metric from the vector. If you have previously kept a handle
    // to that metric (as above), future updates via that handle will go
    // unseen (even if you re-create a metric with the same label set
    // later).
    httpReqs.DeleteLabelValues("200", "GET")
    // Same thing with the more verbose Labels syntax.
    httpReqs.Delete(prometheus.Labels{"method": "GET", "code": "200"})
}

这张图片来自Github上的Promethus examples

要使用vector的值，可以执行以下操作：

    vectorFloat, err := strconv.ParseFloat(vector[0].Value.String(), 64)
    if err != nil {
        panic(err)
    }

    processedTotal.WithLabelValues("ok").Add(vectorFloat)

这是假设你在响应中只会得到一个向量值。向量的值存储为字符串，但您可以使用strconv.ParseFloat方法将其转换为浮点数。