GcpObservabilityConfig: cloud_trace.sampling_rate (#30904)

src/cpp/ext/gcp/observability_config.h

@@ -54,12 +54,14 @@ struct GcpObservabilityConfig {
 
   struct CloudTrace {
     bool enabled = false;
+    float sampling_rate = 0;
 
     static const grpc_core::JsonLoaderInterface* JsonLoader(
         const grpc_core::JsonArgs&) {
       static const auto* loader =
           grpc_core::JsonObjectLoader<CloudTrace>()
               .OptionalField("enabled", &CloudTrace::enabled)
+              .OptionalField("sampling_rate", &CloudTrace::sampling_rate)
               .Finish();
       return loader;
     }

test/cpp/ext/gcp/observability_config_test.cc

@@ -34,7 +34,8 @@ TEST(GcpObservabilityConfigJsonParsingTest, Basic) {
         "enabled": true
       },
       "cloud_trace": {
-        "enabled": true
+        "enabled": true,
+        "sampling_rate": 0.05
       },
       "project_id": "project"
     })json";
@@ -47,6 +48,7 @@ TEST(GcpObservabilityConfigJsonParsingTest, Basic) {
   EXPECT_TRUE(config.cloud_logging.enabled);
   EXPECT_TRUE(config.cloud_monitoring.enabled);
   EXPECT_TRUE(config.cloud_trace.enabled);
+  EXPECT_FLOAT_EQ(config.cloud_trace.sampling_rate, 0.05);
   EXPECT_EQ(config.project_id, "project");
 }