feat: client built in metrics (googleapis#3408)

* feat: client built in metrics

* review comments

* Added environment variable for disabling client metrics

Author: surbhigarg92

google-cloud-spanner/src/main/java/com/google/cloud/spanner/SpannerOptions.java

@@ -706,7 +706,7 @@ default boolean isEnableApiTracing() {
     }
 
     default boolean isEnableBuiltInMetrics() {
-      return false;
+      return true;
     }
 
     default boolean isEnableEndToEndTracing() {
@@ -725,9 +725,9 @@ private static class SpannerEnvironmentImpl implements SpannerEnvironment {
         "SPANNER_OPTIMIZER_STATISTICS_PACKAGE";
     private static final String SPANNER_ENABLE_EXTENDED_TRACING = "SPANNER_ENABLE_EXTENDED_TRACING";
     private static final String SPANNER_ENABLE_API_TRACING = "SPANNER_ENABLE_API_TRACING";
-    private static final String SPANNER_ENABLE_BUILTIN_METRICS = "SPANNER_ENABLE_BUILTIN_METRICS";
     private static final String SPANNER_ENABLE_END_TO_END_TRACING =
         "SPANNER_ENABLE_END_TO_END_TRACING";
+    private static final String SPANNER_DISABLE_BUILTIN_METRICS = "SPANNER_DISABLE_BUILTIN_METRICS";
 
     private SpannerEnvironmentImpl() {}
 
@@ -756,9 +756,7 @@ public boolean isEnableApiTracing() {
 
     @Override
     public boolean isEnableBuiltInMetrics() {
-      // The environment variable SPANNER_ENABLE_BUILTIN_METRICS is used for testing and will be
-      // removed in the future.
-      return Boolean.parseBoolean(System.getenv(SPANNER_ENABLE_BUILTIN_METRICS));
+      return !Boolean.parseBoolean(System.getenv(SPANNER_DISABLE_BUILTIN_METRICS));
     }
 
     @Override
@@ -828,8 +826,8 @@ public static class Builder
     private OpenTelemetry openTelemetry;
     private boolean enableApiTracing = SpannerOptions.environment.isEnableApiTracing();
     private boolean enableExtendedTracing = SpannerOptions.environment.isEnableExtendedTracing();
-    private boolean enableBuiltInMetrics = SpannerOptions.environment.isEnableBuiltInMetrics();
     private boolean enableEndToEndTracing = SpannerOptions.environment.isEnableEndToEndTracing();
+    private boolean enableBuiltInMetrics = SpannerOptions.environment.isEnableBuiltInMetrics();
 
     private static String createCustomClientLibToken(String token) {
       return token + " " + ServiceOptions.getGoogApiClientLibName();
@@ -1410,8 +1408,11 @@ public Builder setEnableApiTracing(boolean enableApiTracing) {
       return this;
     }
 
-    /** Enabling this will enable built in metrics for each individual RPC execution. */
-    Builder setEnableBuiltInMetrics(boolean enableBuiltInMetrics) {
+    /**
+     * Sets whether to enable or disable built in metrics for Data client operations. Built in
+     * metrics are enabled by default.
+     */
+    public Builder setBuiltInMetricsEnabled(boolean enableBuiltInMetrics) {
       this.enableBuiltInMetrics = enableBuiltInMetrics;
       return this;
     }
@@ -1749,7 +1750,7 @@ public boolean isEnableApiTracing() {
    * Returns true if an {@link com.google.api.gax.tracing.MetricsTracer} should be created and set
    * on the Spanner client.
    */
-  boolean isEnableBuiltInMetrics() {
+  public boolean isEnableBuiltInMetrics() {
     return enableBuiltInMetrics;
   }
 

google-cloud-spanner/src/test/java/com/google/cloud/spanner/OpenTelemetryBuiltInMetricsTracerTest.java

@@ -148,7 +148,7 @@ public void createSpannerInstance() {
                     .build())
             // Setting this to false so that Spanner Options does not register Metrics Tracer
             // factory again.
-            .setEnableBuiltInMetrics(false)
+            .setBuiltInMetricsEnabled(false)
             .setApiTracerFactory(metricsTracerFactory)
             .build()
             .getService();