Close released unused connections to the pool when there are no waiters

src/main/java/io/vertx/core/http/impl/pool/Pool.java

@@ -24,6 +24,7 @@
 import io.vertx.core.spi.metrics.HttpClientMetrics;
 
 import java.util.*;
+import java.util.stream.Stream;
 
 /**
  * The endpoint is a queue of waiters and it delegates to the connection pool, the pooling strategy.
@@ -201,6 +202,7 @@ public void onClose(C conn) {
   private synchronized void recycle(ConnectionHolder<C> conn) {
     recycleConnection(conn);
     checkPending();
+    checkClose();
   }
 
   private void recycleConnection(ConnectionHolder<C> conn) {
@@ -263,6 +265,27 @@ private boolean deliverInternal(ConnectionHolder<C> conn, Waiter<C> waiter) {
   }
 
   private void checkClose() {
+    if (waiters.isEmpty()) {
+      if (available.size() > 0) {
+        List<ConnectionHolder<C>> toClose = Collections.emptyList();
+        for (ConnectionHolder<C> conn : available) {
+          if (conn.inflight == 0) {
+            if (toClose.isEmpty()) {
+              toClose = new ArrayList<>();
+            }
+            toClose.add(conn);
+          }
+        }
+        if (toClose.size() > 0) {
+          for (ConnectionHolder<C> conn : toClose) {
+            available.remove(conn);
+            capacity -= conn.concurrency;
+            conn.inflight = (int) conn.concurrency;
+            connector.close(conn.connection);
+          }
+        }
+      }
+    }
     if (all.isEmpty()) {
       // No waiters and no connections - remove the ConnQueue
       if (metrics != null) {

src/test/java/io/vertx/test/core/net/ConnectionManagerTest.java

@@ -112,6 +112,9 @@ public void testConnectPoolEmpty() {
     assertWaitUntil(waiter::isComplete);
     waiter.assertInitialized(conn);
     waiter.assertSuccess(conn);
+    waiter.release();
+    assertEquals(0, mgr.size());
+    assertTrue(mgr.closed());
   }
 
   @Test
@@ -157,7 +160,7 @@ public void testRecycleConnection() {
     FakeWaiter waiter2 = new FakeWaiter();
     mgr.getConnection(waiter2);
     connector.assertRequests(TEST_ADDRESS, 0);
-    waiter1.recycle();
+    waiter1.release();
     assertWaitUntil(waiter2::isComplete);
     waiter2.assertSuccess(conn);
   }
@@ -194,7 +197,7 @@ public void testRecycleInvalidConnection() {
     FakeWaiter waiter2 = new FakeWaiter();
     mgr.getConnection(waiter2);
     conn.invalidate();
-    waiter1.recycle();
+    waiter1.release();
     waitUntil(() -> connector.requests(TEST_ADDRESS) == 1);
     assertFalse(mgr.closed());
     FakeConnection conn2 = connector.assertRequest(TEST_ADDRESS);
@@ -267,10 +270,7 @@ public void testInitialConcurrency() {
     waiters.forEach(waiter -> {
       waitUntil(waiter::isSuccess);
     });
-    waiters.forEach(FakeWaiter::recycle);
-    FakeWaiter waiter = new FakeWaiter();
-    mgr.getConnection(waiter);
-    waitUntil(waiter::isComplete);
+    waiters.forEach(FakeWaiter::release);
   }
 
   @Test
@@ -288,7 +288,7 @@ public void testInitialNoConcurrency() {
     conn.concurrency(0).connect().awaitConnected();
     conn.concurrency(n - 1);
     waitUntil(() -> waiters.stream().filter(FakeWaiter::isSuccess).count() == n - 1);
-    waiters.stream().filter(FakeWaiter::isSuccess).findFirst().get().recycle();
+    waiters.stream().filter(FakeWaiter::isSuccess).findFirst().get().release();
     waiters.forEach(waiter -> {
       waitUntil(waiter::isSuccess);
     });
@@ -357,7 +357,6 @@ public boolean handleConnection(FakeConnection conn) throws Exception {
         } catch (InterruptedException e) {
           e.printStackTrace();
         }
-        System.out.println("DONE");
       });
       actors[i].start();
     }
@@ -443,7 +442,7 @@ public synchronized boolean handleConnection(FakeConnection conn) throws Excepti
       }
     }
 
-    long recycle() {
+    long release() {
       FakeConnection conn = (FakeConnection) result;
       return conn.recycle();
     }
@@ -701,7 +700,7 @@ public long connect(ConnectionListener<FakeConnection> listener,
 
     @Override
     public void close(FakeConnection conn) {
-
+      conn.listener.onClose(conn);
     }
   }
 }