HTTPCLIENT-2318 - Enhance PoolingHttpClientConnectionManager with isShutdown State Check.

This commit introduces an `isShutdown` method to the `PoolingHttpClientConnectionManager` class, providing a thread-safe way to check whether the connection manager has been closed. The addition leverages an existing `AtomicBoolean` closed flag to ensure that the shutdown state can be queried reliably in concurrent environments.

httpclient5/src/main/java/org/apache/hc/client5/http/impl/io/BasicHttpClientConnectionManager.java

@@ -711,8 +711,9 @@ public class BasicHttpClientConnectionManager implements HttpClientConnectionMan
      *
      * @return {@code true} if the connection manager has been shut down and is closed, otherwise
      * return {@code false}.
+     * @since 5.4
      */
-    boolean isClosed() {
+    public boolean isClosed() {
         return this.closed.get();
     }
 

httpclient5/src/main/java/org/apache/hc/client5/http/impl/io/PoolingHttpClientConnectionManager.java

@@ -423,6 +423,11 @@ public class PoolingHttpClientConnectionManager
         if (LOG.isDebugEnabled()) {
             LOG.debug("{} releasing endpoint", ConnPoolSupport.getId(endpoint));
         }
+
+        if (this.isClosed()) {
+            return;
+        }
+
         final ManagedHttpClientConnection conn = entry.getConnection();
         if (conn != null && keepAlive == null) {
             conn.close(CloseMode.GRACEFUL);
@@ -522,11 +527,17 @@ public class PoolingHttpClientConnectionManager
         if (LOG.isDebugEnabled()) {
             LOG.debug("Closing connections idle longer than {}", idleTime);
         }
+        if (isClosed()) {
+            return;
+        }
         this.pool.closeIdle(idleTime);
     }
 
     @Override
     public void closeExpired() {
+        if (isClosed()) {
+            return;
+        }
         LOG.debug("Closing expired connections");
         this.pool.closeExpired();
     }
@@ -796,4 +807,17 @@ public class PoolingHttpClientConnectionManager
 
     }
 
+    /**
+     * Method that can be called to determine whether the connection manager has been shut down and
+     * is closed or not.
+     *
+     * @return {@code true} if the connection manager has been shut down and is closed, otherwise
+     * return {@code false}.
+     * @since 5.4
+     */
+    public boolean isClosed() {
+        return this.closed.get();
+    }
+
+
 }

httpclient5/src/main/java/org/apache/hc/client5/http/impl/nio/PoolingAsyncClientConnectionManager.java

@@ -394,6 +394,9 @@ public class PoolingAsyncClientConnectionManager implements AsyncClientConnectio
         if (LOG.isDebugEnabled()) {
             LOG.debug("{} releasing endpoint", ConnPoolSupport.getId(endpoint));
         }
+        if (this.isClosed()) {
+            return;
+        }
         final ManagedAsyncClientConnection connection = entry.getConnection();
         boolean reusable = connection != null && connection.isOpen();
         try {
@@ -575,11 +578,17 @@ public class PoolingAsyncClientConnectionManager implements AsyncClientConnectio
 
     @Override
     public void closeIdle(final TimeValue idletime) {
+        if (isClosed()) {
+            return;
+        }
         pool.closeIdle(idletime);
     }
 
     @Override
     public void closeExpired() {
+        if (isClosed()) {
+            return;
+        }
         pool.closeExpired();
     }
 
@@ -773,8 +782,9 @@ public class PoolingAsyncClientConnectionManager implements AsyncClientConnectio
      *
      * @return {@code true} if the connection manager has been shut down and is closed, otherwise
      * return {@code false}.
+     * @since 5.4
      */
-    boolean isClosed() {
+    public boolean isClosed() {
         return this.closed.get();
     }
 

httpclient5/src/test/java/org/apache/hc/client5/http/impl/io/TestPoolingHttpClientConnectionManager.java

@@ -30,6 +30,8 @@ package org.apache.hc.client5.http.impl.io;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.Socket;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
@@ -351,4 +353,56 @@ public class TestPoolingHttpClientConnectionManager {
                 socket, "somehost", 443, tlsConfig, context);
     }
 
+    @Test
+    public void testIsShutdownInitially() {
+        Assertions.assertFalse(mgr.isClosed(), "Connection manager should not be shutdown initially.");
+    }
+
+    @Test
+    public void testShutdownIdempotency() {
+        mgr.close();
+        Assertions.assertTrue(mgr.isClosed(), "Connection manager should remain shutdown after the first call to shutdown.");
+        mgr.close(); // Second call to shutdown
+        Assertions.assertTrue(mgr.isClosed(), "Connection manager should still be shutdown after subsequent calls to shutdown.");
+    }
+
+    @Test
+    public void testLeaseAfterShutdown() {
+        mgr.close();
+        Assertions.assertThrows(IllegalArgumentException.class, () -> {
+            // Attempt to lease a connection after shutdown
+            mgr.lease("some-id", new HttpRoute(new HttpHost("localhost")), null);
+        }, "Attempting to lease a connection after shutdown should throw an exception.");
+    }
+
+
+    @Test
+    public void testIsShutdown() {
+        // Setup phase
+        Mockito.when(pool.isShutdown()).thenReturn(false, true); // Simulate changing states
+
+        // Execution phase: Initially, the manager should not be shutdown
+        Assertions.assertFalse(mgr.isClosed(), "Connection manager should not be shutdown initially.");
+
+        // Simulate shutting down the manager
+        mgr.close();
+
+        // Verification phase: Now, the manager should be reported as shutdown
+        Assertions.assertTrue(mgr.isClosed(), "Connection manager should be shutdown after close() is called.");
+    }
+
+
+    @Test
+    public void testConcurrentShutdown() throws InterruptedException {
+        final ExecutorService executor = Executors.newFixedThreadPool(2);
+        // Submit two shutdown tasks to be run in parallel, explicitly calling close() with no arguments
+        executor.submit(() -> mgr.close());
+        executor.submit(() -> mgr.close());
+        executor.shutdown();
+        executor.awaitTermination(1, TimeUnit.SECONDS);
+
+        Assertions.assertTrue(mgr.isClosed(), "Connection manager should be shutdown after concurrent calls to shutdown.");
+    }
+
+
 }