feat: increase default number of channels when gRPC-GCP channel pool …

…is enabled (#1997)

* increase default number of channels when grpc-gcp channel pool is 

* 🦉 Updates from OwlBot post-processor

Co-authored-by: Rajat Bhatta <93644539+rajatbhatta@users.noreply.github.com>
Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

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

@@ -89,6 +89,11 @@ public class SpannerOptions extends ServiceOptions<Spanner, SpannerOptions> {
           "https://www.googleapis.com/auth/spanner.admin",
           "https://www.googleapis.com/auth/spanner.data");
   private static final int MAX_CHANNELS = 256;
+  @VisibleForTesting static final int DEFAULT_CHANNELS = 4;
+  // Set the default number of channels to GRPC_GCP_ENABLED_DEFAULT_CHANNELS when gRPC-GCP extension
+  // is enabled, to make sure there are sufficient channels available to move the sessions to a
+  // different channel if a network connection in a particular channel fails.
+  @VisibleForTesting static final int GRPC_GCP_ENABLED_DEFAULT_CHANNELS = 8;
   private final TransportChannelProvider channelProvider;
 
   @SuppressWarnings("rawtypes")
@@ -669,8 +674,7 @@ public static class Builder
 
     private GrpcInterceptorProvider interceptorProvider;
 
-    /** By default, we create 4 channels per {@link SpannerOptions} */
-    private int numChannels = 4;
+    private Integer numChannels;
 
     private String transportChannelExecutorThreadNameFormat = "Cloud-Spanner-TransportChannel-%d";
 
@@ -1122,8 +1126,7 @@ public Builder setHost(String host) {
 
     /** Enables gRPC-GCP extension with the default settings. */
     public Builder enableGrpcGcpExtension() {
-      this.grpcGcpExtensionEnabled = true;
-      return this;
+      return this.enableGrpcGcpExtension(null);
     }
 
     /**
@@ -1166,6 +1169,11 @@ public SpannerOptions build() {
         // As we are using plain text, we should never send any credentials.
         this.setCredentials(NoCredentials.getInstance());
       }
+      if (this.numChannels == null) {
+        this.numChannels =
+            this.grpcGcpExtensionEnabled ? GRPC_GCP_ENABLED_DEFAULT_CHANNELS : DEFAULT_CHANNELS;
+      }
+
       return new SpannerOptions(this);
     }
   }

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

@@ -20,6 +20,7 @@
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotSame;
 import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertThrows;
 import static org.mockito.Mockito.mock;
@@ -918,4 +919,72 @@ public void testCustomAsyncExecutorProvider() {
             .build();
     assertSame(service, options.getAsyncExecutorProvider().getExecutor());
   }
+
+  @Test
+  public void testDefaultNumChannelsWithGrpcGcpExtensionEnabled() {
+    SpannerOptions options =
+        SpannerOptions.newBuilder().setProjectId("test-project").enableGrpcGcpExtension().build();
+
+    assertEquals(SpannerOptions.GRPC_GCP_ENABLED_DEFAULT_CHANNELS, options.getNumChannels());
+  }
+
+  @Test
+  public void testDefaultNumChannelsWithGrpcGcpExtensionDisabled() {
+    SpannerOptions options = SpannerOptions.newBuilder().setProjectId("test-project").build();
+
+    assertEquals(SpannerOptions.DEFAULT_CHANNELS, options.getNumChannels());
+  }
+
+  @Test
+  public void testNumChannelsWithGrpcGcpExtensionEnabled() {
+    // Set number of channels explicitly, before enabling gRPC-GCP channel pool in SpannerOptions
+    // builder.
+    int numChannels = 5;
+    SpannerOptions options1 =
+        SpannerOptions.newBuilder()
+            .setProjectId("test-project")
+            .setNumChannels(numChannels)
+            .enableGrpcGcpExtension()
+            .build();
+
+    assertEquals(numChannels, options1.getNumChannels());
+
+    // Set number of channels explicitly, after enabling gRPC-GCP channel pool in SpannerOptions
+    // builder.
+    SpannerOptions options2 =
+        SpannerOptions.newBuilder()
+            .setProjectId("test-project")
+            .enableGrpcGcpExtension()
+            .setNumChannels(numChannels)
+            .build();
+
+    assertEquals(numChannels, options2.getNumChannels());
+  }
+
+  @Test
+  public void checkCreatedInstanceWhenGrpcGcpExtensionDisabled() {
+    SpannerOptions options = SpannerOptions.newBuilder().setProjectId("test-project").build();
+    SpannerOptions options1 = options.toBuilder().build();
+    assertEquals(false, options.isGrpcGcpExtensionEnabled());
+    assertEquals(options.isGrpcGcpExtensionEnabled(), options1.isGrpcGcpExtensionEnabled());
+
+    Spanner spanner1 = options.getService();
+    Spanner spanner2 = options1.getService();
+
+    assertNotSame(spanner1, spanner2);
+  }
+
+  @Test
+  public void checkCreatedInstanceWhenGrpcGcpExtensionEnabled() {
+    SpannerOptions options =
+        SpannerOptions.newBuilder().setProjectId("test-project").enableGrpcGcpExtension().build();
+    SpannerOptions options1 = options.toBuilder().build();
+    assertEquals(true, options.isGrpcGcpExtensionEnabled());
+    assertEquals(options.isGrpcGcpExtensionEnabled(), options1.isGrpcGcpExtensionEnabled());
+
+    Spanner spanner1 = options.getService();
+    Spanner spanner2 = options1.getService();
+
+    assertNotSame(spanner1, spanner2);
+  }
 }