Oracle: Lightweight Connection Validation

See #1450

Signed-off-by: Thomas Segismont <tsegismont@gmail.com>

vertx-oracle-client/src/main/java/io/vertx/oracleclient/impl/OracleJdbcConnection.java

@@ -13,6 +13,8 @@
 import io.vertx.core.*;
 import io.vertx.core.internal.ContextInternal;
 import io.vertx.core.internal.PromiseInternal;
+import io.vertx.core.internal.logging.Logger;
+import io.vertx.core.internal.logging.LoggerFactory;
 import io.vertx.core.net.SocketAddress;
 import io.vertx.core.spi.metrics.ClientMetrics;
 import io.vertx.core.tracing.TracingPolicy;
@@ -33,6 +35,8 @@
 
 public class OracleJdbcConnection implements Connection {
 
+  private static final Logger log = LoggerFactory.getLogger(OracleJdbcConnection.class);
+
   private final ClientMetrics metrics;
   private final OracleConnection connection;
   private final OracleMetadata metadata;
@@ -103,7 +107,12 @@ public boolean isSsl() {
 
   @Override
   public boolean isValid() {
-    return true;
+    try {
+      return connection.isValid(OracleConnection.ConnectionValidation.SOCKET, 0);
+    } catch (SQLException e) {
+      log.trace("Failed to validate connection", e);
+      return false;
+    }
   }
 
   @Override