[3.0 Triple] Optimize Connection (#9954)

* opt code of Connection

* add multi connect test case

* opt code of Connection

Co-authored-by: 呈铭 <beck.wcm@antgroup.com>

dubbo-remoting/dubbo-remoting-api/src/main/java/org/apache/dubbo/remoting/api/Connection.java

@@ -175,7 +175,7 @@ public void onConnected(Channel channel) {
         }
         this.channel.set(channel);
         // This indicates that the connection is available.
-        if (this.connectingPromise != null ) {
+        if (this.connectingPromise != null) {
             this.connectingPromise.trySuccess(CONNECTED_OBJECT);
         }
         channel.attr(CONNECTION).set(this);
@@ -192,10 +192,8 @@ public boolean isAvailable() {
         if (channel != null && channel.isActive()) {
             return true;
         }
-        synchronized (this) {
-            if (init.compareAndSet(false, true)) {
-                connect();
-            }
+        if (init.compareAndSet(false, true)) {
+            connect();
         }
 
         this.createConnectingPromise();

dubbo-remoting/dubbo-remoting-api/src/test/java/org/apache/dubbo/remoting/api/ConnectionTest.java

@@ -23,6 +23,8 @@
 import org.junit.jupiter.api.Test;
 
 import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 
 class ConnectionTest {
 
@@ -88,4 +90,36 @@ public void connectSyncTest() throws Throwable {
 
 
     }
+
+    @Test
+    public void testMultiConnect() throws Throwable {
+        int port = NetUtils.getAvailablePort();
+        URL url = URL.valueOf("empty://127.0.0.1:" + port + "?foo=bar");
+        PortUnificationServer server = null;
+        try {
+            server = new PortUnificationServer(url);
+            server.close();
+
+            Connection connection = new Connection(url);
+            ExecutorService service = Executors.newFixedThreadPool(10);
+            final CountDownLatch latch = new CountDownLatch(10);
+            for (int i = 0; i < 10; i++) {
+                Runnable runnable = () -> {
+                    try {
+                        Assertions.assertTrue(connection.isAvailable());
+                        latch.countDown();
+                    } catch (Exception e) {
+                        // ignore
+                    }
+                };
+                service.execute(runnable);
+            }
+        } finally {
+            try {
+                server.close();
+            } catch (Throwable e) {
+                // ignored
+            }
+        }
+    }
 }