Defer frame buffers and metrics until after the BWAPI handshake

Author: dgant

src/main/java/bwapi/BWClient.java

@@ -87,16 +87,17 @@ public void startGame(boolean autoContinue) {
      */
     public void startGame(BWClientConfiguration gameConfiguration) {
         this.configuration = gameConfiguration;
-        this.performanceMetrics = new PerformanceMetrics(configuration);
-        botWrapper = configuration.getAsync()
-                ? new BotWrapperAsync(configuration, eventListener)
-                : new BotWrapper(configuration, eventListener);
 
         if (client == null) {
             client = new Client(this);
         }
         client.reconnect();
 
+        this.performanceMetrics = new PerformanceMetrics(configuration);
+        botWrapper = configuration.getAsync()
+                ? new BotWrapperAsync(configuration, eventListener)
+                : new BotWrapper(configuration, eventListener);
+
         do {
             ClientData.GameData liveGameData = client.liveClientData().gameData();
             while (!liveGameData.isInGame()) {

src/test/java/bwapi/BWClientStartupTest.java

@@ -0,0 +1,49 @@
+package bwapi;
+
+import org.junit.Test;
+
+import java.lang.management.BufferPoolMXBean;
+import java.lang.management.ManagementFactory;
+
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.doAnswer;
+import static org.mockito.Mockito.mock;
+
+/**
+ * Guards the order of startup work: attempt the BWAPI connection before creating
+ * performance metrics or allocating the large buffers used for asynchronous frames.
+ * Measures direct-buffer allocation at a mocked connection boundary, so the test
+ * needs neither a running server nor a machine-dependent elapsed-time threshold.
+ */
+public class BWClientStartupTest {
+    // Stops startGame at the mocked connection boundary, before a game loop can run.
+    private static class StopAfterConnectionAttempt extends RuntimeException {
+    }
+
+    @Test
+    public void attemptsConnectionBeforeAllocatingFrameBuffersOrMetrics() {
+        BWClient bwClient = new BWClient(new DefaultBWListener());
+        Client client = mock(Client.class);
+        bwClient.setClient(client);
+        BWClientConfiguration configuration = new BWClientConfiguration.Builder()
+                .withAsync(true)
+                .withAsyncFrameBufferCapacity(3)
+                .build();
+        BufferPoolMXBean directBuffers = ManagementFactory.getPlatformMXBeans(BufferPoolMXBean.class)
+                .stream()
+                .filter(pool -> "direct".equals(pool.getName()))
+                .findFirst()
+                .get();
+        long bytesBeforeStart = directBuffers.getMemoryUsed();
+        doAnswer(invocation -> {
+            assertTrue("Connection attempts must precede allocation of even one game-state buffer",
+                    directBuffers.getMemoryUsed() - bytesBeforeStart < ClientData.GameData.SIZE);
+            assertNull(bwClient.getPerformanceMetrics());
+            throw new StopAfterConnectionAttempt();
+        }).when(client).reconnect();
+
+        assertThrows(StopAfterConnectionAttempt.class, () -> bwClient.startGame(configuration));
+    }
+}