Activate client stats by default for java 17 services (#9463)

* Activate client stats by default for java 17 services

* Add comments

Author: amarziali

dd-java-agent/instrumentation/okhttp-3/src/test/groovy/IastOkHttp3InstrumentationTest.groovy

@@ -18,6 +18,9 @@ class IastOkHttp3InstrumentationTest extends InstrumentationSpecification {
     // HttpUrl gets loaded early so we have to disable the advice transformer
     IastHttpUrlInstrumentation.ENABLE_ADVICE_TRANSFORMER = false
     injectSysConfig('dd.iast.enabled', 'true')
+    // disable tracer metrics because it uses OkHttp and class loading is
+    // not isolated in tests
+    injectSysConfig("trace.stats.computation.enabled", "false")
   }
 
   @Override

dd-java-agent/instrumentation/okhttp-3/src/test/groovy/OkHttp3Test.groovy

@@ -14,7 +14,7 @@ abstract class OkHttp3Test extends HttpClientTest {
     super.configurePreAgent()
     // disable tracer metrics because it uses OkHttp and class loading is
     // not isolated in tests
-    injectSysConfig("dd.trace.tracer.metrics.enabled", "false")
+    injectSysConfig("trace.stats.computation.enabled", "false")
   }
 
   @Override

internal-api/src/main/java/datadog/trace/api/Config.java

@@ -1812,10 +1812,15 @@ private Config(final ConfigProvider configProvider, final InstrumenterConfig ins
         runtimeMetricsEnabled
             && configProvider.getBoolean(PERF_METRICS_ENABLED, DEFAULT_PERF_METRICS_ENABLED);
 
-    // Enable tracer computed trace metrics by default for Azure Functions
+    // Enable tracer computed trace metrics by default for Azure Functions or for applications using
+    // java 17
+    // We're rolling out progressively CSS so we'll target a slice of the java pool.
+    // That will be removed once will be activated by default
     tracerMetricsEnabled =
         configProvider.getBoolean(
-            TRACE_STATS_COMPUTATION_ENABLED, azureFunctions, TRACER_METRICS_ENABLED);
+            TRACE_STATS_COMPUTATION_ENABLED,
+            azureFunctions || JavaVirtualMachine.isJavaVersion(17),
+            TRACER_METRICS_ENABLED);
     tracerMetricsBufferingEnabled =
         configProvider.getBoolean(TRACER_METRICS_BUFFERING_ENABLED, false);
     tracerMetricsMaxAggregates = configProvider.getInteger(TRACER_METRICS_MAX_AGGREGATES, 2048);