[tracegen] Allow use of adaptive sampling (#5718)

## Which problem is this PR solving?
- Part of #5717

## Description of the changes
- Add a new flag to tracegen to allow it to use `jaegerremotesampling`
contrib module with OTEL SDK

## How was this change tested?
- It's not actually working at the moment, the backend does not
recognize the spans without sampling tags

Signed-off-by: Yuri Shkuro <github@ysh.us>

cmd/tracegen/main.go

@@ -19,8 +19,10 @@ import (
 	"errors"
 	"flag"
 	"fmt"
+	"time"
 
 	"github.com/go-logr/zapr"
+	"go.opentelemetry.io/contrib/samplers/jaegerremote"
 	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/exporters/otlp/otlptrace"
 	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
@@ -39,6 +41,8 @@ import (
 	"github.com/jaegertracing/jaeger/pkg/version"
 )
 
+var flagAdaptiveSamplingEndpoint string
+
 func main() {
 	zc := zap.NewDevelopmentConfig()
 	zc.Level = zap.NewAtomicLevelAt(zapcore.Level(-8)) // level used by OTEL's Debug()
@@ -51,6 +55,14 @@ func main() {
 	fs := flag.CommandLine
 	cfg := new(tracegen.Config)
 	cfg.Flags(fs)
+	fs.StringVar(
+		&flagAdaptiveSamplingEndpoint,
+		"adaptive-sampling",
+		"",
+		"HTTP endpoint to use to retrieve sampling strategies, "+
+			"e.g. http://localhost:14268/api/sampling. "+
+			"When not specified a standard SDK sampler will be used "+
+			"(see OTEL_TRACES_SAMPLER env var in OTEL docs)")
 	flag.Parse()
 
 	logger.Info(version.Get().String())
@@ -94,10 +106,21 @@ func createTracers(cfg *tracegen.Config, logger *zap.Logger) ([]trace.Tracer, fu
 			logger.Sugar().Fatalf("resource creation failed: %s", err)
 		}
 
-		tp := sdktrace.NewTracerProvider(
+		opts := []sdktrace.TracerProviderOption{
 			sdktrace.WithBatcher(exp, sdktrace.WithBlocking()),
 			sdktrace.WithResource(res),
-		)
+		}
+		if flagAdaptiveSamplingEndpoint != "" {
+			jaegerRemoteSampler := jaegerremote.New(
+				svc,
+				jaegerremote.WithSamplingServerURL(flagAdaptiveSamplingEndpoint),
+				jaegerremote.WithSamplingRefreshInterval(5*time.Second),
+				jaegerremote.WithInitialSampler(sdktrace.TraceIDRatioBased(0.5)),
+			)
+			opts = append(opts, sdktrace.WithSampler(jaegerRemoteSampler))
+			logger.Sugar().Infof("using adaptive sampling URL: %s", flagAdaptiveSamplingEndpoint)
+		}
+		tp := sdktrace.NewTracerProvider(opts...)
 		tracers = append(tracers, tp.Tracer(cfg.Service))
 		shutdown = append(shutdown, tp.Shutdown)
 	}

go.mod

@@ -71,6 +71,7 @@ require (
 	go.opentelemetry.io/collector/receiver/otlpreceiver v0.104.0
 	go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.53.0
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.53.0
+	go.opentelemetry.io/contrib/samplers/jaegerremote v0.22.0
 	go.opentelemetry.io/otel v1.28.0
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.28.0
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc v1.28.0

go.sum

@@ -489,6 +489,8 @@ go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.53.0 h1:4K4tsIX
 go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.53.0/go.mod h1:jjdQuTGVsXV4vSs+CJ2qYDeDPf9yIJV23qlIzBm73Vg=
 go.opentelemetry.io/contrib/propagators/b3 v1.27.0 h1:IjgxbomVrV9za6bRi8fWCNXENs0co37SZedQilP2hm0=
 go.opentelemetry.io/contrib/propagators/b3 v1.27.0/go.mod h1:Dv9obQz25lCisDvvs4dy28UPh974CxkahRDUPsY7y9E=
+go.opentelemetry.io/contrib/samplers/jaegerremote v0.22.0 h1:OYxqumWcd1yaV/qvCt1B7Sru9OeUNGjeXq/oldx3AGk=
+go.opentelemetry.io/contrib/samplers/jaegerremote v0.22.0/go.mod h1:2tZTRqCbvx7nG57wUwd5NQpNVujOWnR84iPLllIH0Ok=
 go.opentelemetry.io/contrib/zpages v0.52.0 h1:MPgkMy0Cp3O5EdfVXP0ss3ujhEibysTM4eszx7E7d+E=
 go.opentelemetry.io/contrib/zpages v0.52.0/go.mod h1:fqG5AFdoYru3A3DnhibVuaaEfQV2WKxE7fYE1jgDRwk=
 go.opentelemetry.io/otel v1.28.0 h1:/SqNcYk+idO0CxKEUOtKQClMK/MimZihKYMruSMViUo=

scripts/adaptive-sampling-integration-test.sh

@@ -0,0 +1,17 @@
+#!/bin/bash
+
+set -euf -o pipefail
+
+# This script is currently a placeholder.
+
+# Commands to run integration test:
+#   SAMPLING_STORAGE_TYPE=memory SAMPLING_CONFIG_TYPE=adaptive go run -tags=ui ./cmd/all-in-one --log-level=debug
+#   go run ./cmd/tracegen -adaptive-sampling=http://localhost:14268/api/sampling -pause=10ms -duration=60m
+
+# Check how strategy is changing
+#   curl 'http://localhost:14268/api/sampling?service=tracegen' | jq .
+
+# Issues
+# - SDK does not report sampling probability in the tags the way Jaeger SDKs did
+# - Server probably does not recognize spans as having adaptive sampling without sampler info
+# - There is no way to modify target traces-per-second dynamically, must restart collector.