Prepare connection pool.

We now prepare the pool when the connection factory is started respective the pool has been instantiated.

Closes #3072

src/main/java/org/springframework/data/redis/connection/lettuce/LettucePoolingConnectionProvider.java

@@ -55,6 +55,7 @@ import org.springframework.util.Assert;
  *
  * @author Mark Paluch
  * @author Christoph Strobl
+ * @author Asmir Mustafic
  * @since 2.0
  * @see #getConnection(Class)
  */
@@ -90,8 +91,18 @@ class LettucePoolingConnectionProvider implements LettuceConnectionProvider, Red
 	public <T extends StatefulConnection<?, ?>> T getConnection(Class<T> connectionType) {
 
 		GenericObjectPool<StatefulConnection<?, ?>> pool = pools.computeIfAbsent(connectionType, poolType -> {
-			return ConnectionPoolSupport.createGenericObjectPool(() -> connectionProvider.getConnection(connectionType),
-					poolConfig, false);
+
+			GenericObjectPool<StatefulConnection<?, ?>> newPool = ConnectionPoolSupport
+					.createGenericObjectPool(() -> connectionProvider.getConnection(connectionType), poolConfig, false);
+
+			try {
+				newPool.preparePool();
+
+			} catch (Exception ex) {
+				throw new PoolException("Could not prepare the pool", ex);
+			}
+
+			return newPool;
 		});
 
 		try {

src/test/java/org/springframework/data/redis/connection/lettuce/LettucePoolingConnectionProviderUnitTests.java

@@ -20,6 +20,7 @@ import static org.mockito.Mockito.*;
 import io.lettuce.core.api.StatefulRedisConnection;
 import io.lettuce.core.api.async.RedisAsyncCommands;
 
+import org.apache.commons.pool2.impl.GenericObjectPoolConfig;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
@@ -27,11 +28,13 @@ import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
 import org.mockito.junit.jupiter.MockitoSettings;
 import org.mockito.quality.Strictness;
+import org.springframework.data.redis.connection.lettuce.LettucePoolingClientConfiguration.LettucePoolingClientConfigurationBuilder;
 
 /**
  * Unit tests for {@link LettucePoolingConnectionProvider}.
  *
  * @author Mark Paluch
+ * @author Asmir Mustafic
  */
 @ExtendWith(MockitoExtension.class)
 @MockitoSettings(strictness = Strictness.LENIENT)
@@ -70,4 +73,21 @@ class LettucePoolingConnectionProviderUnitTests {
 
 		verify(commandsMock).discard();
 	}
+
+	@Test
+	void shouldPrepareThePool() {
+
+		GenericObjectPoolConfig poolConfig = new GenericObjectPoolConfig();
+		poolConfig.setMinIdle(5);
+		poolConfig.setMaxIdle(8);
+		poolConfig.setMaxTotal(10);
+
+		LettucePoolingClientConfiguration config = new LettucePoolingClientConfigurationBuilder().poolConfig(poolConfig)
+				.build();
+
+		LettucePoolingConnectionProvider provider = new LettucePoolingConnectionProvider(connectionProviderMock, config);
+
+		provider.getConnection(StatefulRedisConnection.class);
+		verify(connectionProviderMock, times(5)).getConnection(any());
+	}
 }