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Metrics

Metrics middleware is used to monitor performance metrics for services, counting request time and request counts.

Configuration​

Two configuration methods are available in metrics middleware WithSeconds() and WithRequests()。

WithSeconds()​

func WithSeconds(c metrics.Observer) Option {
    return func(o *options) {
        o.seconds = c
    }
}

The Observer histogram used to set up the metrics middleware statistics request.

WithRequests()​

func WithRequests(c metrics.Counter) Option {
    return func(o *options) {
        o.requests = c
    }
}

The Counter counter used to set the metrics middleware statistics request count.

Usage (kratos < 2.8.0)​

Prometheus​

// Detailed reference https://github.com/go-kratos/examples/tree/main/metrics

_metricSeconds = prometheus.NewHistogramVec(prometheus.HistogramOpts{
    Namespace: "server",
    Subsystem: "requests",
    Name:      "duration_sec",
    Help:      "server requests duratio(sec).",
    Buckets:   []float64{0.005, 0.01, 0.025, 0.05, 0.1, 0.250, 0.5, 1},
}, []string{"kind", "operation"})

_metricRequests = prometheus.NewCounterVec(prometheus.CounterOpts{
    Namespace: "client",
    Subsystem: "requests",
    Name:      "code_total",
    Help:      "The total number of processed requests",
}, []string{"kind", "operation", "code", "reason"})
    
prometheus.MustRegister(_metricSeconds, _metricRequests)

To configure metrics in servers​

import (
    prom "github.com/go-kratos/kratos/contrib/metrics/prometheus/v2"
)

// grpc service
grpcSrv := grpc.NewServer(
    grpc.Address(":9000"),
    grpc.Middleware(
        metrics.Server(
            metrics.WithSeconds(prom.NewHistogram(_metricSeconds)),
            metrics.WithRequests(prom.NewCounter(_metricRequests)),
        ),
    ),
)

// http service
httpSrv := http.NewServer(
    http.Address(":8000"),
    http.Middleware(
        metrics.Server(
            metrics.WithSeconds(prom.NewHistogram(_metricSeconds)),
            metrics.WithRequests(prom.NewCounter(_metricRequests)),
        ),
    ),
)
httpSrv.Handle("/metrics", promhttp.Handler())

To configure metrics in clients​

// grpc client
conn, err := grpc.DialInsecure(
    context.Background(),
    grpc.WithEndpoint("127.0.0.1:9000"),
    grpc.WithMiddleware(
        metrics.Client(
            metrics.WithSeconds(prom.NewHistogram(_metricSeconds)),
            metrics.WithRequests(prom.NewCounter(_metricRequests)),
        ),
    ),
)

// http client
conn, err := http.NewClient(
    context.Background(),
    http.WithEndpoint("127.0.0.1:8000"),
    http.WithMiddleware(
        metrics.Client(
            metrics.WithSeconds(prom.NewHistogram(_metricSeconds)),
            metrics.WithRequests(prom.NewCounter(_metricRequests)),
        ),
    ),
)

Usage (kratos >= 2.8.0)​

Since version v2.8.0, kratos uses otel.Metrics. Way to export metrics to prometheus is as follows:

Prometheus​

import (
    "github.com/go-kratos/kratos/v2/middleware/metrics"
    "go.opentelemetry.io/otel/exporters/prometheus"
    "go.opentelemetry.io/otel/metric"
    sdkmetric "go.opentelemetry.io/otel/sdk/metric"
)

// Detailed reference https://github.com/go-kratos/examples/tree/main/metrics
func init() {
    exporter, err := prometheus.New()
    if err != nil {
        panic(err)
    }
    provider := sdkmetric.NewMeterProvider(sdkmetric.WithReader(exporter))
    meter := provider.Meter(Name)

    _metricRequests, err = metrics.DefaultRequestsCounter(meter, metrics.DefaultServerRequestsCounterName)
    if err != nil {
        panic(err)
    }

    _metricSeconds, err = metrics.DefaultSecondsHistogram(meter, metrics.DefaultServerSecondsHistogramName)
    if err != nil {
        panic(err)
    }
}

To configure metrics in servers​

import (
    "github.com/prometheus/client_golang/prometheus/promhttp"
)

// grpc service
grpcSrv := grpc.NewServer(
    grpc.Address(":9000"),
    grpc.Middleware(
        metrics.Server(
            metrics.WithSeconds(_metricSeconds),
            metrics.WithRequests(_metricRequests),
        ),
    ),
)

// http service
httpSrv := http.NewServer(
    http.Address(":8000"),
    http.Middleware(
        metrics.Server(
            metrics.WithSeconds(_metricSeconds),
            metrics.WithRequests(_metricRequests),
        ),
    ),
)
httpSrv.Handle("/metrics", promhttp.Handler())

To configure metrics in clients​

// grpc client
conn, err := grpc.DialInsecure(
    context.Background(),
    grpc.WithEndpoint("127.0.0.1:9000"),
    grpc.WithMiddleware(
        metrics.Client(
            metrics.WithSeconds(_metricSeconds),
            metrics.WithRequests(_metricRequests),
        ),
    ),
)

// http client
conn, err := http.NewClient(
    context.Background(),
    http.WithEndpoint("127.0.0.1:8000"),
    http.WithMiddleware(
        metrics.Client(
            metrics.WithSeconds(_metricSeconds),
            metrics.WithRequests(_metricRequests),
        ),
    ),
)

References​