feat: Add sample code for connection pooling

Author: cindy-peng

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

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2025 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.datastore;
+
+// [START datastore_configure_connection_pool]
+
+import com.google.api.gax.grpc.ChannelPoolSettings;
+import com.google.api.gax.grpc.InstantiatingGrpcChannelProvider;
+import com.google.cloud.datastore.DatastoreOptions;
+import com.google.cloud.datastore.v1.DatastoreSettings;
+import com.google.cloud.grpc.GrpcTransportOptions;
+
+
+public class ConfigureConnectionPool {
+
+  public static void main(String... args) throws Exception {
+    InstantiatingGrpcChannelProvider channelProvider =
+        DatastoreSettings.defaultGrpcTransportProviderBuilder()
+            .setChannelPoolSettings(
+                ChannelPoolSettings.builder()
+                    .setInitialChannelCount(10)
+                    .setMinChannelCount(5)
+                    .setMaxChannelCount(200)
+                    .build())
+            .build();
+
+    DatastoreOptions datastoreOptions = DatastoreOptions.newBuilder()
+        .setProjectId("my-project")
+        .setChannelProvider(channelProvider)
+        .setTransportOptions(GrpcTransportOptions.newBuilder().build())
+        .build();
+
+    ChannelPoolSettings channelPoolSettings =
+        ((InstantiatingGrpcChannelProvider) datastoreOptions.getTransportChannelProvider())
+            .getChannelPoolSettings();
+
+    System.out.printf(String.format(
+        "Connected with pool with InitialChannelCount: %d, MinChannelCount: %d, MaxChannelCount: %d",
+        channelPoolSettings.getInitialChannelCount(), channelPoolSettings.getMinChannelCount(),
+        channelPoolSettings.getMaxChannelCount()
+    ));
+  }
+}
+
+// [END datastore_configure_connection_pool]

samples/snippets/src/test/java/com/example/datastore/ConfigureConnectionPoolIT.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * 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.datastore;
+
+import com.rule.SystemsOutRule;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/**
+ * Tests for ConfigureConnectionPool sample.
+ */
+@RunWith(JUnit4.class)
+@SuppressWarnings("checkstyle:abbreviationaswordinname")
+public class ConfigureConnectionPoolIT {
+
+  @Rule
+  public final SystemsOutRule systemsOutRule = new SystemsOutRule();
+
+  @Test
+  public void testConfigureConnectionPool() throws Exception {
+    ConfigureConnectionPool.main();
+    systemsOutRule.assertContains(
+        "Connected with pool with InitialChannelCount: 10, MinChannelCount: 5, MaxChannelCount: 200");
+  }
+}