Make trace context interceptor conditional based on client opt-in

Author: nareshz

google-cloud-spanner/src/main/java/com/google/cloud/spanner/spi/v1/GapicSpannerRpc.java

@@ -348,6 +348,8 @@ public GapicSpannerRpc(final SpannerOptions options) {
                           MoreObjects.firstNonNull(
                               options.getInterceptorProvider(),
                               SpannerInterceptorProvider.createDefault(options.getOpenTelemetry())))
+                      // This sets the trace context headers.
+                      .withTraceContext(serverSideTracingEnabled, options.getOpenTelemetry())
                       // This sets the response compressor (Server -> Client).
                       .withEncoding(compressorName))
               .setHeaderProvider(headerProviderWithUserAgent)

google-cloud-spanner/src/main/java/com/google/cloud/spanner/spi/v1/SpannerInterceptorProvider.java

@@ -51,7 +51,6 @@ public static SpannerInterceptorProvider createDefault(OpenTelemetry openTelemet
     defaultInterceptorList.add(
         new LoggingInterceptor(Logger.getLogger(GapicSpannerRpc.class.getName()), Level.FINER));
     defaultInterceptorList.add(new HeaderInterceptor(new SpannerRpcMetrics(openTelemetry)));
-    defaultInterceptorList.add(new TraceContextInterceptor(openTelemetry));
     return new SpannerInterceptorProvider(ImmutableList.copyOf(defaultInterceptorList));
   }
 
@@ -75,6 +74,13 @@ SpannerInterceptorProvider withEncoding(String encoding) {
     return this;
   }
 
+  SpannerInterceptorProvider withTraceContext(boolean serverSideTracingEnabled, OpenTelemetry openTelemetry) {
+    if (serverSideTracingEnabled) {
+      return with(new TraceContextInterceptor(openTelemetry));
+    }
+    return this;
+  }
+
   @Override
   public List<ClientInterceptor> getInterceptors() {
     return clientInterceptors;

google-cloud-spanner/src/test/java/com/google/cloud/spanner/spi/v1/GapicSpannerRpcTest.java

@@ -631,15 +631,15 @@ public void testCustomUserAgent() {
   }
 
   @Test
-  public void testTraceContextHeaderWithOpenTelemetry() {
+  public void testTraceContextHeaderWithOpenTelemetryAndServerSideTracingEnabled() {
     OpenTelemetry openTelemetry =
         OpenTelemetrySdk.builder()
             .setPropagators(ContextPropagators.create(W3CTraceContextPropagator.getInstance()))
             .setTracerProvider(SdkTracerProvider.builder().setSampler(Sampler.alwaysOn()).build())
             .build();
 
     final SpannerOptions options =
-        createSpannerOptions().toBuilder().setOpenTelemetry(openTelemetry).build();
+        createSpannerOptions().toBuilder().setOpenTelemetry(openTelemetry).enableServerSideTracing().build();
     try (Spanner spanner = options.getService()) {
       final DatabaseClient databaseClient =
           spanner.getDatabaseClient(DatabaseId.of("[PROJECT]", "[INSTANCE]", "[DATABASE]"));
@@ -652,6 +652,28 @@ public void testTraceContextHeaderWithOpenTelemetry() {
     }
   }
 
+  @Test
+  public void testTraceContextHeaderWithOpenTelemetryAndServerSideTracingDisabled() {
+    OpenTelemetry openTelemetry =
+        OpenTelemetrySdk.builder()
+            .setPropagators(ContextPropagators.create(W3CTraceContextPropagator.getInstance()))
+            .setTracerProvider(SdkTracerProvider.builder().setSampler(Sampler.alwaysOn()).build())
+            .build();
+
+    final SpannerOptions options =
+        createSpannerOptions().toBuilder().setOpenTelemetry(openTelemetry).disableServerSideTracing().build();
+    try (Spanner spanner = options.getService()) {
+      final DatabaseClient databaseClient =
+          spanner.getDatabaseClient(DatabaseId.of("[PROJECT]", "[INSTANCE]", "[DATABASE]"));
+
+      try (final ResultSet rs = databaseClient.singleUse().executeQuery(SELECT1AND2)) {
+        rs.next();
+      }
+
+      assertFalse(isTraceContextPresent);
+    }
+  }
+
   @Test
   public void testTraceContextHeaderWithoutOpenTelemetry() {
     final SpannerOptions options = createSpannerOptions();