fix(core): inconsistency connection state

CHANGELOG.md

@@ -7,6 +7,12 @@
 - Fixed a bug: the timeout in IProtoBegin was being specified in milliseconds (as a `long`), but
   the [protocol](https://www.tarantool.io/ru/doc/latest/reference/internals/iproto/streams/#iproto-begin)
   requires the timeout to be passed in seconds (as a `double`).
+- Fixed a bug where the `Connection#connect()` method would leave the connection in a `CONNECTING` 
+  state if a failure occurred before the channel was created (for example, when an 
+  invalid—non-positive—timeout value was provided). As a result, all subsequent calls to this 
+  method would return `null` instead of a `CompletableFuture`. The method now always returns a 
+  `CompletableFuture` object, which either completes successfully (upon receipt of a greeting) or 
+  terminates with an error. Providing not positive timeout value throws an exception.
 
 ### Documentation
 

tarantool-core/src/main/java/io/tarantool/core/connection/ConnectionImpl.java

@@ -181,6 +181,10 @@ public Connection listen(Consumer<IProtoResponse> listener) {
   @Override
   public synchronized CompletableFuture<Greeting> connect(InetSocketAddress address, long timeoutMs)
       throws IllegalStateException {
+    if (timeoutMs <= 0) {
+      throw new IllegalArgumentException("Timeout must be greater than zero!");
+    }
+
     if (state.compareAndSet(State.CLOSED, State.CONNECTING)) {
       closedBy.set(CloseReason.NO_REASON);
       log.debug("{} is connecting to {}", this, address);
@@ -407,9 +411,6 @@ private void fire(ConnectionCloseEvent event, Throwable ex) {
 
   private void scheduleGreetingTimeout(CompletableFuture<Greeting> promise, long timeoutMs) {
     log.debug("Schedule timeout for connect in milliseconds: {}", timeoutMs);
-    if (timeoutMs <= 0) {
-      throw new IllegalStateException("Timeout must be greater than zero!");
-    }
     timeoutHandler =
         this.timerService.newTimeout(
             timeoutHandler -> {

tarantool-core/src/test/java/io/tarantool/core/integration/ConnectionToTarantoolTest.java

@@ -34,6 +34,7 @@
 import static org.msgpack.value.ValueFactory.newMap;
 import io.netty.channel.ConnectTimeoutException;
 import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.RepeatedTest;
 import org.junit.jupiter.api.Test;
@@ -390,6 +391,31 @@ public void testConnectAndSendByMultipleThreads() throws InterruptedException {
     assertEquals(CONCURRENT_THREADS_COUNT, success);
   }
 
+  /**
+   * This test checks for an inconsistent state caused by passing a non-positive timeout during a
+   * connection attempt, followed by a subsequent attempt to connect.
+   */
+  @Test
+  void testConnectWithNonPositiveTimeoutForFirstAttempt() throws Exception {
+    try (Connection connection = factory.create()) {
+      InetSocketAddress address = tt.mappedAddress();
+
+      Assertions.assertThrows(
+          IllegalArgumentException.class, () -> connection.connect(address, -1L));
+
+      final CompletableFuture<Greeting> connectionFuture = connection.connect(address, 1_000L);
+      Assertions.assertNotNull(connectionFuture, "Connection future must be not null!");
+
+      final Greeting greeting = connectionFuture.join();
+      Assertions.assertNotNull(greeting, "Greeting must be not null!");
+      Assertions.assertTrue(connection.isConnected(), "Connection must be connected");
+
+      final Greeting secondGreeting = connection.connect(address, 5_000L).join();
+
+      Assertions.assertSame(greeting, secondGreeting, "Must be same!");
+    }
+  }
+
   private IProtoRequest createSelectRequest(int syncId) {
     Map<Value, Value> rawHeader = new HashMap<>();
     rawHeader.put(newInteger(IPROTO_REQUEST_TYPE), newInteger(IPROTO_SELECT));