isValid() timeout should not be blocked

pgjdbc/src/main/java/org/postgresql/jdbc/PgConnection.java

@@ -1427,7 +1427,6 @@ public boolean isValid(int timeout) throws SQLException {
           if (checkConnectionQuery == null) {
             checkConnectionQuery = prepareStatement("");
           }
-          checkConnectionQuery.setQueryTimeout(timeout);
           checkConnectionQuery.executeUpdate();
         }
         return true;

pgjdbc/src/test/java/org/postgresql/jdbc/ConnectionValidTest.java

@@ -0,0 +1,154 @@
+/*
+ * Copyright (c) 2020, PostgreSQL Global Development Group
+ * See the LICENSE file in the project root for more information.
+ */
+
+package org.postgresql.jdbc;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.postgresql.test.TestUtil;
+import org.postgresql.test.util.rules.annotation.HaveMinimalServerVersion;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.Timeout;
+
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.net.ServerSocket;
+import java.net.Socket;
+import java.sql.Connection;
+import java.util.Properties;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+
+@HaveMinimalServerVersion("9.4")
+public class ConnectionValidTest {
+
+  @Rule
+  public Timeout timeout = new Timeout(30, TimeUnit.SECONDS);
+
+  private static final int LOCAL_SHADOW_PORT = 9009;
+
+  private Connection connection;
+
+  private ConnectionBreaker connectionBreaker;
+
+  @Before
+  public void setUp() throws Exception {
+    final Properties shadowProperties = new Properties();
+    shadowProperties.setProperty(TestUtil.SERVER_HOST_PORT_PROP,
+        String.format("%s:%s", "localhost", LOCAL_SHADOW_PORT));
+
+    connectionBreaker = new ConnectionBreaker(LOCAL_SHADOW_PORT,
+        TestUtil.getServer(),
+        TestUtil.getPort());
+    connectionBreaker.acceptAsyncConnection();
+    connection = TestUtil.openDB(shadowProperties);
+  }
+
+  @After
+  public void tearDown() throws Exception {
+    connectionBreaker.close();
+    connection.close();
+  }
+
+  /**
+   * Tests if a connection is valid within 5 seconds.
+   * @throws Exception if a database exception occurs.
+   */
+  @Test
+  public void testIsValid() throws Exception {
+    connectionBreaker.breakConnection();
+    boolean result = connection.isValid(5);
+
+    assertThat("Is connection valid?",
+        result,
+        equalTo(false)
+    );
+  }
+
+  private static final class ConnectionBreaker {
+
+    private final ExecutorService workers;
+
+    private final ServerSocket internalServer;
+
+    private final Socket pgSocket;
+
+    private boolean breakConnection;
+
+    /**
+     * Constructor of the forwarder for the PostgreSQL server.
+     *
+     * @param serverPort The forwarder server port.
+     * @param pgServer   The PostgreSQL server address.
+     * @param pgPort     The PostgreSQL server port.
+     * @throws Exception if anything goes wrong binding the server.
+     */
+    ConnectionBreaker(final int serverPort, final String pgServer,
+        final int pgPort) throws Exception {
+      workers = Executors.newCachedThreadPool();
+      internalServer = new ServerSocket(serverPort);
+      pgSocket = new Socket(pgServer, pgPort);
+      breakConnection = false;
+    }
+
+    /**
+     * Starts to accept a asynchronous connection.
+     *
+     * @throws Exception if something goes wrong with the sockets.
+     */
+    public void acceptAsyncConnection() throws Exception {
+      final InputStream pgServerInputStream = pgSocket.getInputStream();
+      final OutputStream pgServerOutputStream = pgSocket.getOutputStream();
+
+      // Future socket;
+      final Future<Socket> futureConnection = workers.submit(internalServer::accept);
+
+      // Forward reads;
+      workers.submit(() -> {
+        while (!breakConnection) {
+          final Socket conn = futureConnection.get();
+          int read = pgServerInputStream.read();
+          conn.getOutputStream().write(read);
+        }
+        return null;
+      });
+
+      // Forwards writes;
+      workers.submit(() -> {
+        while (!breakConnection) {
+          final Socket conn = futureConnection.get();
+          int read = conn.getInputStream().read();
+          pgServerOutputStream.write(read);
+        }
+        return null;
+      });
+    }
+
+    /**
+     * Breaks the forwarding.
+     */
+    public void breakConnection() {
+      this.breakConnection = true;
+    }
+
+    /**
+     * Closes the sockets.
+     */
+    public void close() throws Exception {
+      this.workers.shutdown();
+      this.workers.awaitTermination(5, TimeUnit.SECONDS);
+      this.internalServer.close();
+      this.pgSocket.close();
+    }
+
+  }
+}