jaegerremote: Add WithSamplingStrategyFetcher option (#4045)

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
+
+- Do not panic when the default HTTP round-tripper is not `*http.Transport`. (#4045)
 
 ## [1.20.0/0.45.0/0.14.0] - 2023-09-28
 

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

@@ -46,7 +46,7 @@ func TestRemotelyControlledSampler_updateConcurrentSafe(t *testing.T) {
 		WithInitialSampler(initSampler),
 		WithSamplingServerURL("my url"),
 		WithSamplingRefreshInterval(time.Millisecond),
-		withSamplingStrategyFetcher(fetcher),
+		WithSamplingStrategyFetcher(fetcher),
 		withSamplingStrategyParser(parser),
 		withUpdaters(updaters...),
 	)
@@ -80,8 +80,7 @@ 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 +116,7 @@ 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 +301,7 @@ 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 +333,8 @@ func TestRemotelyControlledSampler_multiStrategyResponse(t *testing.T) {
 					Operation: testUnusedOpName,
 					ProbabilisticSampling: &jaeger_api_v2.ProbabilisticSamplingStrategy{
 						SamplingRate: testUnusedOpSamplingRate,
-					}},
+					},
+				},
 			},
 		},
 	}
@@ -586,3 +586,8 @@ 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)
+}