chore: add env var for enabling api tracing

Author: olavloite

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

@@ -690,6 +690,10 @@ default String getOptimizerStatisticsPackage() {
     default boolean isEnableExtendedTracing() {
       return false;
     }
+
+    default boolean isEnableApiTracing() {
+      return false;
+    }
   }
 
   /**
@@ -702,6 +706,7 @@ private static class SpannerEnvironmentImpl implements SpannerEnvironment {
     private static final String SPANNER_OPTIMIZER_STATISTICS_PACKAGE_ENV_VAR =
         "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 SpannerEnvironmentImpl() {}
 
@@ -722,6 +727,11 @@ public String getOptimizerStatisticsPackage() {
     public boolean isEnableExtendedTracing() {
       return Boolean.parseBoolean(System.getenv(SPANNER_ENABLE_EXTENDED_TRACING));
     }
+
+    @Override
+    public boolean isEnableApiTracing() {
+      return Boolean.parseBoolean(System.getenv(SPANNER_ENABLE_API_TRACING));
+    }
   }
 
   /** Builder for {@link SpannerOptions} instances. */
@@ -785,7 +795,7 @@ public static class Builder
     private DirectedReadOptions directedReadOptions;
     private boolean useVirtualThreads = false;
     private OpenTelemetry openTelemetry;
-    private boolean enableApiTracing = false;
+    private boolean enableApiTracing = SpannerOptions.environment.isEnableApiTracing();
     private boolean enableExtendedTracing = SpannerOptions.environment.isEnableExtendedTracing();
 
     private static String createCustomClientLibToken(String token) {

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

@@ -29,6 +29,7 @@
 import com.google.cloud.NoCredentials;
 import com.google.cloud.spanner.MockSpannerServiceImpl.SimulatedExecutionTime;
 import com.google.cloud.spanner.MockSpannerServiceImpl.StatementResult;
+import com.google.cloud.spanner.SpannerOptions.SpannerEnvironment;
 import com.google.cloud.spanner.connection.RandomResultSetGenerator;
 import com.google.common.collect.ImmutableList;
 import com.google.spanner.admin.database.v1.UpdateDatabaseDdlMetadata;
@@ -408,6 +409,46 @@ public void testLroOperationFailed() {
     assertEquals(StatusCode.ERROR, updateDatabaseDdlOperation.getStatus().getStatusCode());
   }
 
+  @Test
+  public void testEnableWithEnvVar() {
+    SpannerOptions.useEnvironment(
+        new SpannerEnvironment() {
+          @Override
+          public boolean isEnableApiTracing() {
+            return true;
+          }
+        });
+    // Create a Spanner instance without explicitly enabling API tracing.
+    Spanner spanner =
+        SpannerOptions.newBuilder()
+            .setProjectId("test-project")
+            .setChannelProvider(channelProvider)
+            .setCredentials(NoCredentials.getInstance())
+            .setSessionPoolOption(
+                SessionPoolOptions.newBuilder()
+                    .setWaitForMinSessions(Duration.ofSeconds(5L))
+                    .setFailOnSessionLeak()
+                    .build())
+            .build()
+            .getService();
+    DatabaseClient client = spanner.getDatabaseClient(DatabaseId.of("p", "i", "d"));
+
+    try (ResultSet resultSet = client.singleUse().executeQuery(SELECT_RANDOM)) {
+      assertTrue(resultSet.next());
+      assertFalse(resultSet.next());
+    }
+
+    assertEquals(CompletableResultCode.ofSuccess(), spanExporter.flush());
+    List<SpanData> spans = spanExporter.getFinishedSpanItems();
+    assertContains("CloudSpanner.ReadOnlyTransaction", spans);
+    assertContains("CloudSpannerOperation.ExecuteStreamingQuery", spans);
+    assertContains("Spanner.ExecuteStreamingSql", spans);
+    assertParent(
+        "CloudSpanner.ReadOnlyTransaction", "CloudSpannerOperation.ExecuteStreamingQuery", spans);
+    assertParent(
+        "CloudSpannerOperation.ExecuteStreamingQuery", "Spanner.ExecuteStreamingSql", spans);
+  }
+
   void assertContains(String expected, List<SpanData> spans) {
     assertTrue(
         "Expected " + spansToString(spans) + " to contain " + expected,

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

@@ -769,7 +769,7 @@ public void testRetryOnExecuteSql() {
         .run(transaction -> transaction.executeUpdate(UPDATE_STATEMENT));
 
     assertEquals(2, mockSpanner.countRequestsOfType(ExecuteSqlRequest.class));
-    int numExpectedSpans = isMultiplexedSessionsEnabled() ? 9 : 7;
+    int numExpectedSpans = isMultiplexedSessionsEnabled() ? 10 : 8;
     waitForFinishedSpans(numExpectedSpans);
     List<SpanData> finishedSpans = spanExporter.getFinishedSpanItems();
     List<String> finishedSpanNames =