Add multiple tracing propagators

This commit adds more tracing propagators to allow the system to work with both
W3C tracing context and the "old" Jaeger tracing context that Prometheus still
uses. This is a combination of future proofing and compatibility.

go.mod

@@ -12,6 +12,7 @@ require (
 	github.com/thanos-io/thanos v0.12.1
 	go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.16.0
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.16.0
+	go.opentelemetry.io/contrib/propagators v0.16.0 // indirect
 	go.opentelemetry.io/otel v0.16.0
 	go.opentelemetry.io/otel/exporters/trace/jaeger v0.16.0
 	golang.org/x/sys v0.0.0-20210104204734-6f8348627aad // indirect

go.sum

@@ -910,12 +910,15 @@ go.opencensus.io v0.22.2/go.mod h1:yxeiOL68Rb0Xd1ddK5vPZ/oVn4vY4Ynel7k9FzqtOIw=
 go.opencensus.io v0.22.3/go.mod h1:yxeiOL68Rb0Xd1ddK5vPZ/oVn4vY4Ynel7k9FzqtOIw=
 go.opencensus.io v0.22.4/go.mod h1:yxeiOL68Rb0Xd1ddK5vPZ/oVn4vY4Ynel7k9FzqtOIw=
 go.opencensus.io v0.22.5/go.mod h1:5pWMHQbX5EPX2/62yrJeAkowc+lfs/XD7Uxpq3pI6kk=
+go.opentelemetry.io v0.1.0 h1:EANZoRCOP+A3faIlw/iN6YEWoYb1vleZRKm1EvH8T48=
 go.opentelemetry.io/contrib v0.16.0 h1:cScR/U3bjTjxsBv939wh4miANY/akdP644rsg9msrIA=
 go.opentelemetry.io/contrib v0.16.0/go.mod h1:G/EtFaa6qaN7+LxqfIAT3GiZa7Wv5DTBUzl5H4LY0Kc=
 go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.16.0 h1:Px1Aq1dWypvYhuuvb2Y0sL8j66L6GDKfVECP8/QMMZ0=
 go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.16.0/go.mod h1:hFqINJwGPTvDeAdDVxQXV+5HV944veeLbuexbZeVeqs=
 go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.16.0 h1:hPbUH5fugPACtUdBWGL5glNqzowwHvnOdnwvQOATWgM=
 go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.16.0/go.mod h1:dNF4PMGeouMEPAWDwgEjsGFlod9hAU8oj0TU0w2J19g=
+go.opentelemetry.io/contrib/propagators v0.16.0 h1:6M16whHin+Uz2zMefuxmFG5CITQ2Q1CHnt2vKxWcQ+A=
+go.opentelemetry.io/contrib/propagators v0.16.0/go.mod h1:5kVVCrfVbGf6mu9Lk6DS91EDrkdneQdqUkJhmZXrOrA=
 go.opentelemetry.io/otel v0.16.0 h1:uIWEbdeb4vpKPGITLsRVUS44L5oDbDUCZxn8lkxhmgw=
 go.opentelemetry.io/otel v0.16.0/go.mod h1:e4GKElweB8W2gWUqbghw0B8t5MCTccc9212eNHnOHwA=
 go.opentelemetry.io/otel/exporters/trace/jaeger v0.16.0 h1:gOnjphv9uycs+AfZprppdsm/P7B0CVxPr5E1UtT2wqw=

main.go

@@ -21,10 +21,13 @@ import (
 	"github.com/thanos-io/thanos/pkg/store/storepb"
 	"go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc"
 	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/propagation"
 	"go.opentelemetry.io/otel/trace"
 	"google.golang.org/grpc"
 
 	grpc_prometheus "github.com/grpc-ecosystem/go-grpc-prometheus"
+	jaegerPropagator "go.opentelemetry.io/contrib/propagators/jaeger"
 	jaegerExporter "go.opentelemetry.io/otel/exporters/trace/jaeger"
 )
 
@@ -60,6 +63,12 @@ func initTracer() func() {
 		log.Fatal(err)
 	}
 
+	otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(
+		jaegerPropagator.Jaeger{},
+		propagation.TraceContext{},
+		propagation.Baggage{},
+	))
+
 	return flush
 }