docs: Sample for configuring connection pool

Author: billyjacobson

samples/snippets/src/main/java/com/example/bigtable/ConfigureConnectionPool.java

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+/*
+ * Copyright 2021 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.bigtable;
+
+// [START bigtable_configure_connection_pool]
+
+import com.google.api.gax.grpc.InstantiatingGrpcChannelProvider;
+import com.google.cloud.bigtable.data.v2.BigtableDataClient;
+import com.google.cloud.bigtable.data.v2.BigtableDataSettings;
+import com.google.cloud.bigtable.data.v2.stub.EnhancedBigtableStubSettings;
+
+public class ConfigureConnectionPool {
+
+  public static void configureConnectionPool(String projectId, String instanceId) {
+    // String projectId = "my-project-id";
+    // String instanceId = "my-instance-id";
+
+    BigtableDataSettings.Builder settingsBuilder = BigtableDataSettings.newBuilder()
+        .setProjectId(projectId)
+        .setInstanceId(instanceId);
+
+    settingsBuilder.stubSettings()
+        .setTransportChannelProvider(
+            EnhancedBigtableStubSettings.defaultGrpcTransportProviderBuilder()
+                .setPoolSize(250)
+                .build());
+
+    BigtableDataSettings settings = settingsBuilder.build();
+    try (BigtableDataClient dataClient = BigtableDataClient.create(settings)) {
+      InstantiatingGrpcChannelProvider provider =
+          (InstantiatingGrpcChannelProvider) settings.getStubSettings()
+              .getTransportChannelProvider();
+
+      int poolSize = provider.toBuilder().getPoolSize();
+
+      System.out.println(String.format("Connected with pool size of %d", poolSize));
+    } catch (Exception e) {
+      System.out.println("Error during ConfigureConnectionPool: \n" + e.toString());
+    }
+  }
+}
+
+// [END bigtable_configure_connection_pool]

samples/snippets/src/test/java/com/example/bigtable/ConfigureConnectionPoolTest.java

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+/*
+ * Copyright 2021 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.bigtable;
+
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertThat;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import org.hamcrest.CoreMatchers;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.FixMethodOrder;
+import org.junit.Test;
+import org.junit.runners.MethodSorters;
+
+@FixMethodOrder(MethodSorters.NAME_ASCENDING)
+public class ConfigureConnectionPoolTest {
+
+  private static final String INSTANCE_ENV = "BIGTABLE_TESTING_INSTANCE";
+  private static String projectId;
+  private static String instanceId;
+  private ByteArrayOutputStream bout;
+
+  private static String requireEnv(String varName) {
+    String value = System.getenv(varName);
+    assertNotNull(
+        String.format("Environment variable '%s' is required to perform these tests.", varName),
+        value);
+    return value;
+  }
+
+  @BeforeClass
+  public static void beforeClass() {
+    projectId = requireEnv("GOOGLE_CLOUD_PROJECT");
+    instanceId = requireEnv(INSTANCE_ENV);
+  }
+
+  @Before
+  public void setupStream() {
+    bout = new ByteArrayOutputStream();
+    System.setOut(new PrintStream(bout));
+  }
+
+  @Test
+  public void testConfigureConnectionPool() {
+    ConfigureConnectionPool.configureConnectionPool(projectId, instanceId);
+
+    String output = bout.toString();
+    assertThat(output, CoreMatchers.containsString("Connected with pool size of 250"));
+  }
+}