Reuse BalancedResolverGroup.INSTANCE for TCP clients.

We now also register a Shutdown hook to close BalancedResolverGroup.

[resolves #412]

Signed-off-by: Mark Paluch <[email protected]>

Author: mp911de

src/main/java/io/r2dbc/postgresql/client/BalancedResolverGroup.java

@@ -30,13 +30,21 @@
  * @since 0.8.6
  */
 final class BalancedResolverGroup extends AddressResolverGroup<InetSocketAddress> {
+
     BalancedResolverGroup() {
     }
 
-    public static final BalancedResolverGroup INSTANCE = new BalancedResolverGroup();
+    public static final BalancedResolverGroup INSTANCE;
+
+    static {
+
+        INSTANCE = new BalancedResolverGroup();
+        Runtime.getRuntime().addShutdownHook(new Thread(INSTANCE::close, "R2DBC-Postgresql-BalancedResolverGroup-ShutdownHook"));
+    }
 
     @Override
     protected AddressResolver<InetSocketAddress> newResolver(EventExecutor executor) throws Exception {
         return new RoundRobinInetAddressResolver(executor, new DefaultNameResolver(executor)).asAddressResolver();
     }
+
 }

src/main/java/io/r2dbc/postgresql/client/ReactorNettyClient.java

@@ -373,7 +373,7 @@ public static Mono<ReactorNettyClient> connect(SocketAddress socketAddress, Conn
                 tcpClient = tcpClient.runOn(settings.getRequiredLoopResources());
             }
 
-            tcpClient = tcpClient.resolver(new BalancedResolverGroup());
+            tcpClient = tcpClient.resolver(BalancedResolverGroup.INSTANCE);
             tcpClient = tcpClient.option(ChannelOption.SO_KEEPALIVE, settings.isTcpKeepAlive());
             tcpClient = tcpClient.option(ChannelOption.TCP_NODELAY, settings.isTcpNoDelay());
         }