docs: fix tracing sample to exit when completed, and use custom monitored resource for export (#3287)

* docs: fix tracing sample to exit when completed, and use custom monitored resource for export

* add comments and reorder ops

* chore: generate libraries at Fri Oct 25 05:15:57 UTC 2024

* update comment as per findings

---------

Co-authored-by: cloud-java-bot <[email protected]>

Author: rahul2393

README.md

@@ -19,7 +19,7 @@ If you are using Maven with [BOM][libraries-bom], add this to your pom.xml file:
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>libraries-bom</artifactId>
-      <version>26.48.0</version>
+      <version>26.49.0</version>
       <type>pom</type>
       <scope>import</scope>
     </dependency>

samples/snippets/src/main/java/com/example/spanner/TracingSample.java

@@ -16,13 +16,16 @@
 
 package com.example.spanner;
 
+import com.google.api.MonitoredResource;
+import com.google.cloud.MetadataConfig;
 import com.google.cloud.spanner.DatabaseClient;
 import com.google.cloud.spanner.DatabaseId;
 import com.google.cloud.spanner.ResultSet;
 import com.google.cloud.spanner.Spanner;
 import com.google.cloud.spanner.SpannerOptions;
 import com.google.cloud.spanner.Statement;
 import com.google.cloud.spanner.spi.v1.SpannerRpcViews;
+import io.opencensus.common.Duration;
 import io.opencensus.common.Scope;
 import io.opencensus.contrib.grpc.metrics.RpcViews;
 import io.opencensus.contrib.zpages.ZPageHandlers;
@@ -32,11 +35,15 @@
 import io.opencensus.trace.samplers.Samplers;
 import java.util.Arrays;
 
-/** This sample demonstrates how to enable opencensus tracing and stats in cloud spanner client. 
+/**
+ * This sample demonstrates how to enable opencensus tracing and stats in cloud spanner client.
  *
- * @deprecated The OpenCensus project is deprecated. Use OpenTelemetry to enable metrics 
- * and stats with cloud spanner client. 
-*/
+ * @deprecated The OpenCensus project is deprecated. Use OpenTelemetry to enable metrics and stats
+ *     with cloud spanner client.
+ *     <p>Note: This sample uses System.exit(0) to ensure clean termination because the
+ *     ZPageHandlers HTTP server (localhost:8080/tracez) uses non-daemon threads and does not
+ *     provide a public stop() method.
+ */
 public class TracingSample {
 
   private static final String SAMPLE_SPAN = "CloudSpannerSample";
@@ -58,7 +65,13 @@ public static void main(String[] args) throws Exception {
         .registerSpanNamesForCollection(Arrays.asList(SAMPLE_SPAN));
 
     // Installs an exporter for stack driver stats.
-    StackdriverStatsExporter.createAndRegister();
+    MonitoredResource.Builder builder = MonitoredResource.newBuilder();
+    if (MetadataConfig.getProjectId() != null) {
+      builder.putLabels("project_id", options.getProjectId());
+    }
+    builder.setType("global");
+    StackdriverStatsExporter.createAndRegisterWithProjectIdAndMonitoredResource(
+        options.getProjectId(), Duration.create(60L, 0), builder.build());
     RpcViews.registerAllGrpcViews();
     // Capture GFE Latency and GFE Header missing count.
     SpannerRpcViews.registerGfeLatencyAndHeaderMissingCountViews();
@@ -85,8 +98,19 @@ public static void main(String[] args) throws Exception {
         }
       }
     } finally {
-      // Closes the client which will free up the resources used
+      // First, shutdown the stats/metrics exporters
+      StackdriverStatsExporter.unregister();
+
+      // Shutdown tracing components
+      StackdriverExporter.unregister();
+      Tracing.getExportComponent().shutdown();
+
+      // Close the spanner client
       spanner.close();
+
+      // Force immediate exit since ZPageHandlers.startHttpServerAndRegisterAll(8080)
+      // starts a non-daemon HTTP server thread that cannot be stopped gracefully
+      System.exit(0);
     }
   }
 }