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// Copyright 2023 The Prometheus 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 main
import (
"context"
"encoding/json"
"flag"
"fmt"
"log"
"net/http"
httppprof "net/http/pprof"
"os"
"syscall"
"time"
"github.com/bwplotka/tracing-go/tracing"
"github.com/bwplotka/tracing-go/tracing/exporters/otlp"
tracinghttp "github.com/bwplotka/tracing-go/tracing/http"
"github.com/efficientgo/core/errcapture"
"github.com/efficientgo/core/errors"
"github.com/oklog/run"
"github.com/prometheus/common/model"
"github.com/prometheus/client_golang/api"
v1 "github.com/prometheus/client_golang/api/prometheus/v1"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/tutorials/whatsup/internal"
)
func main() {
opts, err := internal.ParseOptions(os.Args)
if err != nil {
log.Fatalf("Error: %v", err)
}
if err := runMain(opts); err != nil {
// Use %+v for github.com/efficientgo/core/errors error to print with stack.
log.Fatalf("Error: %+v", errors.Wrapf(err, "%s", flag.Arg(0)))
}
}
func runMain(opts internal.Config) (err error) {
// Create tracer, so the application can be instrumented with traces.
var exporter tracing.ExporterBuilder
switch opts.TraceEndpoint {
case "stdout":
exporter = tracing.NewWriterExporter(os.Stdout)
default:
exporter = otlp.Exporter(opts.TraceEndpoint, otlp.WithInsecure())
}
tracer, closeFn, err := tracing.NewTracer(
exporter,
tracing.WithSampler(tracing.TraceIDRatioBasedSampler(opts.TraceSamplingRatio)),
tracing.WithServiceName("client_golang-tutorial:whatsup"),
)
if err != nil {
return err
}
defer errcapture.Do(&err, closeFn, "close tracers")
m := http.NewServeMux()
// Create HTTP handler for Prometheus metrics.
// TODO
//m.Handle("/metrics", ...
promClient, err := api.NewClient(api.Config{
Client: &http.Client{Transport: instrumentRoundTripper(nil, "prometheus", http.DefaultTransport)},
Address: opts.PrometheusAddr,
})
if err != nil {
return err
}
apiClient := v1.NewAPI(promClient)
// Create HTTP handler for our whatsup implementation.
m.HandleFunc(instrumentHandlerFunc(tracer, nil, "/whatsup", whatsUpHandler(
apiClient,
)))
// Debug profiling endpoints.
m.HandleFunc("/debug/pprof/", httppprof.Index)
m.HandleFunc("/debug/pprof/cmdline", httppprof.Cmdline)
m.HandleFunc("/debug/pprof/profile", httppprof.Profile)
m.HandleFunc("/debug/pprof/symbol", httppprof.Symbol)
srv := http.Server{Addr: fmt.Sprintf(":%v", internal.WhatsupPort), Handler: m}
g := &run.Group{}
g.Add(func() error {
log.Println("Starting HTTP server", "addr", internal.WhatsupPort)
if err := srv.ListenAndServe(); err != nil {
return errors.Wrap(err, "starting web server")
}
return nil
}, func(error) {
if err := srv.Close(); err != nil {
log.Println("Error: Failed to stop web server", "err", err)
}
})
g.Add(run.SignalHandler(context.Background(), syscall.SIGINT, syscall.SIGTERM))
return g.Run()
}
type response struct {
Error error `json:",omitempty"`
Instances []string
}
// whatsUpHandler returns all services that currently monitored by Prometheus.
// It uses prometheus client_golang client code to request PromQL query against given Prometheus server
// to return answer.
func whatsUpHandler(
apiClient v1.API,
) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
ctx := r.Context()
w.Header().Set("Content-Type", "application/json")
var upResponse model.Value
if err := tracing.DoInSpan(ctx, "query Prometheus", func(ctx context.Context) error {
res, warn, err := apiClient.Query(ctx, "up", time.Now())
if err != nil {
return err
}
if len(warn) > 0 {
return errors.Newf("got warnings from Prometheus %v", warn)
}
upResponse = res
return nil
}); err != nil {
// We return OK status, so browser can render nice result.
w.WriteHeader(http.StatusOK)
// NOTE: Pass-through error might be not always safe, sanitize on production.
b, _ := json.Marshal(response{Error: err})
_, _ = fmt.Fprintln(w, string(b))
return
}
resp := response{}
switch r := upResponse.(type) {
case model.Vector:
for _, s := range r {
resp.Instances = append(resp.Instances, string(s.Metric["instance"]))
}
}
w.WriteHeader(http.StatusOK)
b, _ := json.Marshal(resp)
_, _ = fmt.Fprintln(w, string(b))
}
}
func getExemplarFn(ctx context.Context) prometheus.Labels {
if spanCtx := tracing.GetSpan(ctx); spanCtx.Context().IsSampled() {
return prometheus.Labels{"traceID": spanCtx.Context().TraceID()}
}
return nil
}
func instrumentHandlerFunc(tracer *tracing.Tracer, _ prometheus.Registerer, handlerName string, handler http.Handler) (string, http.HandlerFunc) {
// Wrap with tracing. This will be visited as a first middleware.
base := tracinghttp.NewMiddleware(tracer).WrapHandler(handlerName, http.HandlerFunc(func(writer http.ResponseWriter, r *http.Request) {
handler.ServeHTTP(writer, r)
}))
return handlerName, base.ServeHTTP
}
func instrumentRoundTripper(_ prometheus.Registerer, clientName string, rt http.RoundTripper) http.RoundTripper {
// Wrap with tracing. This will be visited as a first middleware.
return tracinghttp.NewTripperware().WrapRoundTipper(clientName, rt)
}
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