trace.go

/*
 * Copyright 2022 CloudWeGo Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package prometheus

import (
	"context"
	"net/http"
	"strconv"

	"github.com/cloudwego/hertz/pkg/common/hlog"
	"github.com/prometheus/client_golang/prometheus/promhttp"

	"github.com/cloudwego/hertz/pkg/app"
	"github.com/cloudwego/hertz/pkg/common/tracer"
	"github.com/cloudwego/hertz/pkg/common/tracer/stats"
	prom "github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/collectors"
)

const (
	labelMethod     = "method"
	labelStatusCode = "statusCode"
	labelPath       = "path"

	unknownLabelValue = "unknown"
)

// genLabels make labels values.
func genLabels(ctx *app.RequestContext) prom.Labels {
	labels := make(prom.Labels)
	labels[labelMethod] = defaultValIfEmpty(string(ctx.Request.Method()), unknownLabelValue)
	labels[labelStatusCode] = defaultValIfEmpty(strconv.Itoa(ctx.Response.Header.StatusCode()), unknownLabelValue)
	labels[labelPath] = defaultValIfEmpty(ctx.FullPath(), unknownLabelValue)

	return labels
}

type serverTracer struct {
	serverHandledCounter   *prom.CounterVec
	serverHandledHistogram *prom.HistogramVec
}

// Start record the beginning of server handling request from client.
func (s *serverTracer) Start(ctx context.Context, c *app.RequestContext) context.Context {
	return ctx
}

// Finish record the ending of server handling request from client.
func (s *serverTracer) Finish(ctx context.Context, c *app.RequestContext) {
	if c.GetTraceInfo().Stats().Level() == stats.LevelDisabled {
		return
	}

	httpStart := c.GetTraceInfo().Stats().GetEvent(stats.HTTPStart)
	httpFinish := c.GetTraceInfo().Stats().GetEvent(stats.HTTPFinish)
	if httpFinish == nil || httpStart == nil {
		return
	}
	cost := httpFinish.Time().Sub(httpStart.Time())
	_ = counterAdd(s.serverHandledCounter, 1, genLabels(c))
	_ = histogramObserve(s.serverHandledHistogram, cost, genLabels(c))
}

// NewServerTracer provides tracer for server access, addr and path is the scrape_configs for prometheus server.
func NewServerTracer(addr, path string, opts ...Option) tracer.Tracer {
	cfg := defaultConfig()

	for _, opts := range opts {
		opts.apply(cfg)
	}

	if !cfg.disableServer {
		http.Handle(path, promhttp.HandlerFor(cfg.registry, promhttp.HandlerOpts{ErrorHandling: promhttp.ContinueOnError}))
		go func() {
			if err := http.ListenAndServe(addr, nil); err != nil {
				hlog.Fatal("HERTZ: Unable to start a promhttp server, err: " + err.Error())
			}
		}()
	}

	serverHandledCounter := prom.NewCounterVec(
		prom.CounterOpts{
			Name: "hertz_server_throughput",
			Help: "Total number of HTTPs completed by the server, regardless of success or failure.",
		},
		[]string{labelMethod, labelStatusCode, labelPath},
	)
	cfg.registry.MustRegister(serverHandledCounter)

	serverHandledHistogram := prom.NewHistogramVec(
		prom.HistogramOpts{
			Name:    "hertz_server_latency_us",
			Help:    "Latency (microseconds) of HTTP that had been application-level handled by the server.",
			Buckets: cfg.buckets,
		},
		[]string{labelMethod, labelStatusCode, labelPath},
	)
	cfg.registry.MustRegister(serverHandledHistogram)

	if cfg.enableGoCollector {
		cfg.registry.MustRegister(collectors.NewGoCollector(collectors.WithGoCollectorRuntimeMetrics(cfg.runtimeMetricRules...)))
	}

	return &serverTracer{
		serverHandledCounter:   serverHandledCounter,
		serverHandledHistogram: serverHandledHistogram,
	}
}

func defaultValIfEmpty(val, def string) string {
	if val == "" {
		return def
	}
	return val
}