jaegerremote: Add WithSamplingStrategyFetcher option

CHANGELOG.md

@@ -11,6 +11,11 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 ### Added
 
 - Add the new `go.opentelemetry.io/contrib/instrgen` package to provide auto-generated source code instrumentation. (#3068, #3108)
+- Add `WithSamplingStrategyFetcher` which sets custom fetcher implementation. (#4045)
+
+### Fixed
+
+- Fixed panic when default HTTP round-tripper is not `*http.Transport` (#4045)
 
 ## [1.18.0/0.43.0/0.12.0] - 2023-08-28
 
@@ -19,6 +24,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Add `NewMiddleware` function in `go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp`. (#2964)
 - The `go.opentelemetry.io/contrib/exporters/autoexport` package to provide configuration of trace exporters with useful defaults and environment variable support. (#2753, #4100, #4130, #4132, #4134)
 - `WithRouteTag` in `go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp` adds HTTP route attribute to metrics. (#615)
+
 - Add `WithSpanOptions` option in `go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc`. (#3768)
 - Add testing support for Go 1.21. (#4233)
 

samplers/jaegerremote/sampler_remote.go

@@ -39,8 +39,8 @@ const (
 	defaultSamplingOperationNameLateBinding = true
 )
 
-// samplingStrategyFetcher is used to fetch sampling strategy updates from remote server.
-type samplingStrategyFetcher interface {
+// SamplingStrategyFetcher is used to fetch sampling strategy updates from remote server.
+type SamplingStrategyFetcher interface {
 	Fetch(service string) ([]byte, error)
 }
 
@@ -273,13 +273,10 @@ type httpSamplingStrategyFetcher struct {
 }
 
 func newHTTPSamplingStrategyFetcher(serverURL string) *httpSamplingStrategyFetcher {
-	customTransport := http.DefaultTransport.(*http.Transport).Clone()
-	customTransport.ResponseHeaderTimeout = defaultRemoteSamplingTimeout
-
 	return &httpSamplingStrategyFetcher{
 		serverURL: serverURL,
 		httpClient: http.Client{
-			Transport: customTransport,
+			Timeout: defaultRemoteSamplingTimeout,
 		},
 	}
 }

samplers/jaegerremote/sampler_remote_options.go

@@ -28,7 +28,7 @@ type config struct {
 	sampler                 trace.Sampler
 	samplingServerURL       string
 	samplingRefreshInterval time.Duration
-	samplingFetcher         samplingStrategyFetcher
+	samplingFetcher         SamplingStrategyFetcher
 	samplingParser          samplingStrategyParser
 	updaters                []samplerUpdater
 	posParams               perOperationSamplerParams
@@ -123,8 +123,10 @@ func WithLogger(logger logr.Logger) Option {
 	})
 }
 
-// samplingStrategyFetcher creates a Option that initializes sampling strategy fetcher.
-func withSamplingStrategyFetcher(fetcher samplingStrategyFetcher) Option {
+// WithSamplingStrategyFetcher creates an Option that initializes the sampling strategy fetcher.
+// Custom fetcher can be used for setting custom headers, timeouts, etc., or getting
+// sampling strategies from a different source, like files.
+func WithSamplingStrategyFetcher(fetcher SamplingStrategyFetcher) Option {
 	return optionFunc(func(c *config) {
 		c.samplingFetcher = fetcher
 	})

samplers/jaegerremote/sampler_remote_test.go

@@ -20,6 +20,7 @@ import (
 	"encoding/binary"
 	"errors"
 	"fmt"
+	"net/http"
 	"sync"
 	"testing"
 	"time"
@@ -46,7 +47,7 @@ func TestRemotelyControlledSampler_updateConcurrentSafe(t *testing.T) {
 		WithInitialSampler(initSampler),
 		WithSamplingServerURL("my url"),
 		WithSamplingRefreshInterval(time.Millisecond),
-		withSamplingStrategyFetcher(fetcher),
+		WithSamplingStrategyFetcher(fetcher),
 		withSamplingStrategyParser(parser),
 		withUpdaters(updaters...),
 	)
@@ -80,8 +81,7 @@ func (c *testSamplingStrategyFetcher) Fetch(serviceName string) ([]byte, error)
 	return c.response, nil
 }
 
-type testSamplingStrategyParser struct {
-}
+type testSamplingStrategyParser struct{}
 
 func (p *testSamplingStrategyParser) Parse(response []byte) (interface{}, error) {
 	strategy := new(jaeger_api_v2.SamplingStrategyResponse)
@@ -117,7 +117,7 @@ func TestRemoteSamplerOptions(t *testing.T) {
 		WithInitialSampler(initSampler),
 		WithSamplingServerURL("my url"),
 		WithSamplingRefreshInterval(42*time.Second),
-		withSamplingStrategyFetcher(fetcher),
+		WithSamplingStrategyFetcher(fetcher),
 		withSamplingStrategyParser(parser),
 		withUpdaters(updaters...),
 		WithLogger(logger),
@@ -302,7 +302,7 @@ func TestRemotelyControlledSampler_ImmediatelyUpdateOnStartup(t *testing.T) {
 		WithInitialSampler(initSampler),
 		WithSamplingServerURL("my url"),
 		WithSamplingRefreshInterval(10*time.Minute),
-		withSamplingStrategyFetcher(fetcher),
+		WithSamplingStrategyFetcher(fetcher),
 		withSamplingStrategyParser(parser),
 		withUpdaters(updaters...),
 	)
@@ -334,7 +334,8 @@ func TestRemotelyControlledSampler_multiStrategyResponse(t *testing.T) {
 					Operation: testUnusedOpName,
 					ProbabilisticSampling: &jaeger_api_v2.ProbabilisticSamplingStrategy{
 						SamplingRate: testUnusedOpSamplingRate,
-					}},
+					},
+				},
 			},
 		},
 	}
@@ -586,3 +587,21 @@ func TestSamplingStrategyParserImpl_Error(t *testing.T) {
 	require.Error(t, err, "output: %+v", val)
 	require.Contains(t, err.Error(), `unknown value "foo_bar"`)
 }
+
+func TestDefaultSamplingStrategyFetcher_Timeout(t *testing.T) {
+	fetcher := newHTTPSamplingStrategyFetcher("")
+	assert.Equal(t, defaultRemoteSamplingTimeout, fetcher.httpClient.Timeout)
+}
+
+func TestDefaultSamplingStrategyFetcher_NoPanic(t *testing.T) {
+	defaultTransport := http.DefaultTransport
+	http.DefaultTransport = http.NewFileTransport(http.Dir("/"))
+
+	t.Cleanup(func() {
+		http.DefaultTransport = defaultTransport
+	})
+
+	require.NotPanics(t, func() {
+		newHTTPSamplingStrategyFetcher("")
+	})
+}