Adds tracing sample for cloud spanner

spanner/cloud-client/pom.xml

@@ -52,12 +52,16 @@ limitations under the License.
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-spanner</artifactId>
-      <version>0.32.0-beta</version>
+      <version>0.33.0-beta</version>
       <exclusions>
-        <exclusion> <!-- exclude an old version of Guava -->
+        <exclusion>
           <groupId>com.google.guava</groupId>
           <artifactId>guava-jdk5</artifactId>
         </exclusion>
+        <exclusion>
+          <groupId>io.opencensus</groupId>
+          <artifactId>opencensus-api</artifactId>
+        </exclusion>
       </exclusions>
     </dependency>
 
@@ -66,6 +70,31 @@ limitations under the License.
       <artifactId>guava</artifactId>
       <version>20.0</version>
     </dependency>
+    <dependency>
+        <groupId>io.opencensus</groupId>
+        <artifactId>opencensus-api</artifactId>
+        <version>0.11.0</version>
+    </dependency>
+    <dependency>
+        <groupId>io.opencensus</groupId>
+        <artifactId>opencensus-impl</artifactId>
+        <version>0.11.0</version>
+    </dependency>
+    <dependency>
+        <groupId>io.opencensus</groupId>
+        <artifactId>opencensus-contrib-zpages</artifactId>
+        <version>0.11.0</version>
+    </dependency>
+    <dependency>
+        <groupId>io.opencensus</groupId>
+        <artifactId>opencensus-exporter-trace-logging</artifactId>
+        <version>0.11.0</version>
+    </dependency>
+    <dependency>
+        <groupId>io.opencensus</groupId>
+        <artifactId>opencensus-exporter-trace-stackdriver</artifactId>
+        <version>0.11.0</version>
+    </dependency>
 
     <!-- Test dependencies -->
     <dependency>

spanner/cloud-client/src/main/java/com/example/spanner/TracingSample.java

@@ -0,0 +1,60 @@
+package com.example.spanner;
+
+import java.util.Arrays;
+
+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 io.opencensus.common.Scope;
+import io.opencensus.contrib.zpages.ZPageHandlers;
+import io.opencensus.exporter.trace.stackdriver.StackdriverExporter;
+import io.opencensus.trace.Tracing;
+import io.opencensus.trace.samplers.Samplers;
+
+public class TracingSample {
+
+  public static void main(String[] args) throws Exception {	
+    if (args.length != 2) {
+      System.err.println("Usage: TracingSample <instance_id> <database_id>");
+      return;
+    }
+    SpannerOptions options = SpannerOptions.newBuilder().build();
+    Spanner spanner = options.getService();
+
+    // Installs a handler for /tracez page.
+    ZPageHandlers.startHttpServerAndRegisterAll(8080);
+    // Installs an exporter for stack driver.
+    StackdriverExporter.createAndRegister();
+    Tracing.getExportComponent().getSampledSpanStore().registerSpanNamesForCollection(Arrays.asList("CloudSpannerSample"));
+
+    // Name of your instance & database.
+    String instanceId = args[0];
+    String databaseId = args[1];
+    try {
+      // Creates a database client
+      DatabaseClient dbClient = spanner.getDatabaseClient(DatabaseId.of(
+          options.getProjectId(), instanceId, databaseId));
+      // Queries the database
+      try (Scope ss = Tracing.getTracer()
+          .spanBuilderWithExplicitParent("CloudSpannerSample", null)
+          .setSampler(Samplers.alwaysSample())
+          .startScopedSpan()) {
+        ResultSet resultSet = dbClient.singleUse().executeQuery(Statement.of("SELECT 1"));
+
+        System.out.println("\n\nResults:");
+        // Prints the results
+        while (resultSet.next()) {
+          System.out.printf("%d\n\n", resultSet.getLong(0));
+        }
+      }
+    } finally {
+      // Closes the client which will free up the resources used
+      spanner.close();
+    }
+  }
+
+}