Fix lease timeout race to prevent pool entry leak (#649)

Author: arturobernalg

httpcore5/src/main/java/org/apache/hc/core5/pool/LaxConnPool.java

@@ -466,8 +466,10 @@ public PoolEntry<T, C> get(
                     try {
                         return super.get(timeout, unit);
                     } catch (final TimeoutException ex) {
-                        cancel();
-                        throw ex;
+                        if (cancel()) {
+                            throw ex;
+                        }
+                        return super.get();
                     }
                 }
 

httpcore5/src/main/java/org/apache/hc/core5/pool/RouteSegmentedConnPool.java

@@ -173,6 +173,19 @@ final class Waiter extends CompletableFuture<PoolEntry<R, C>> {
             this.cancelled = false;
             this.timeoutTask = null;
         }
+
+        @Override
+        public PoolEntry<R, C> get(final long timeout, final TimeUnit unit)
+                throws InterruptedException, java.util.concurrent.ExecutionException, TimeoutException {
+            try {
+                return super.get(timeout, unit);
+            } catch (final TimeoutException ex) {
+                if (cancel(true)) {
+                    throw ex;
+                }
+                return super.get();
+            }
+        }
     }
 
     @Override

httpcore5/src/main/java/org/apache/hc/core5/pool/StrictConnPool.java

@@ -177,8 +177,10 @@ public PoolEntry<T, C> get(
                 try {
                     return super.get(timeout, unit);
                 } catch (final TimeoutException ex) {
-                    cancel();
-                    throw ex;
+                    if (cancel()) {
+                        throw ex;
+                    }
+                    return super.get();
                 }
             }
 

httpcore5/src/test/java/org/apache/hc/core5/pool/TestStrictConnPoolLeaseTimeoutRace.java

@@ -0,0 +1,160 @@
+/*
+ * ====================================================================
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ *
+ */
+package org.apache.hc.core5.pool;
+
+import java.io.IOException;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeoutException;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Supplier;
+import java.util.stream.Stream;
+
+import org.apache.hc.core5.http.SocketModalCloseable;
+import org.apache.hc.core5.io.CloseMode;
+import org.apache.hc.core5.util.TimeValue;
+import org.apache.hc.core5.util.Timeout;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.MethodSource;
+
+class TestConnPoolLeaseTimeout {
+
+    private static final Timeout TIMEOUT = Timeout.ofSeconds(30);
+
+    static final class DummyConn implements SocketModalCloseable {
+
+        private volatile Timeout socketTimeout;
+
+        @Override
+        public Timeout getSocketTimeout() {
+            return socketTimeout;
+        }
+
+        @Override
+        public void setSocketTimeout(final Timeout timeout) {
+            this.socketTimeout = timeout;
+        }
+
+        @Override
+        public void close(final CloseMode closeMode) {
+        }
+
+        @Override
+        public void close() throws IOException {
+        }
+    }
+
+    static final class PoolCase {
+        final String name;
+        final Supplier<ManagedConnPool<String, DummyConn>> supplier;
+
+        PoolCase(final String name, final Supplier<ManagedConnPool<String, DummyConn>> supplier) {
+            this.name = name;
+            this.supplier = supplier;
+        }
+
+        @Override
+        public String toString() {
+            return name;
+        }
+    }
+
+    static Stream<PoolCase> pools() {
+        return Stream.of(
+                new PoolCase("STRICT", () -> new StrictConnPool<>(1, 1)),
+                new PoolCase("LAX", () -> new LaxConnPool<>(1)),
+                new PoolCase("OFFLOCK", () -> new RouteSegmentedConnPool<>(
+                        1,
+                        1,
+                        TimeValue.NEG_ONE_MILLISECOND,
+                        PoolReusePolicy.LIFO,
+                        new DefaultDisposalCallback<>()))
+        );
+    }
+
+    @ParameterizedTest(name = "{0}")
+    @MethodSource("pools")
+    @org.junit.jupiter.api.Timeout(60)
+    void testLeaseTimeoutDoesNotLeakLeasedEntries(final PoolCase poolCase) throws Exception {
+        final ManagedConnPool<String, DummyConn> pool = poolCase.supplier.get();
+
+        final String route = "route-1";
+        final Timeout requestTimeout = Timeout.ofMicroseconds(1);
+
+        final int concurrentThreads = 10;
+        final CountDownLatch countDownLatch = new CountDownLatch(concurrentThreads);
+        final AtomicLong n = new AtomicLong(concurrentThreads * 100);
+
+        final ExecutorService executorService = Executors.newFixedThreadPool(concurrentThreads);
+        final AtomicReference<Exception> unexpectedException = new AtomicReference<>();
+        try {
+            for (int i = 0; i < concurrentThreads; i++) {
+                executorService.execute(() -> {
+                    try {
+                        while (n.decrementAndGet() > 0) {
+                            final Future<PoolEntry<String, DummyConn>> f = pool.lease(route, null, requestTimeout, null);
+                            try {
+                                final PoolEntry<String, DummyConn> entry =
+                                        f.get(requestTimeout.getDuration(), requestTimeout.getTimeUnit());
+                                pool.release(entry, true);
+                            } catch (final InterruptedException ex) {
+                                Thread.currentThread().interrupt();
+                                unexpectedException.compareAndSet(null, ex);
+                            } catch (final TimeoutException ex) {
+                                f.cancel(true);
+                            } catch (final ExecutionException ex) {
+                                f.cancel(true);
+                                if (!(ex.getCause() instanceof TimeoutException)) {
+                                    unexpectedException.compareAndSet(null, ex);
+                                }
+                            }
+                        }
+                    } finally {
+                        countDownLatch.countDown();
+                    }
+                });
+            }
+
+            Assertions.assertTrue(countDownLatch.await(TIMEOUT.getDuration(), TIMEOUT.getTimeUnit()));
+            Assertions.assertTrue(n.get() <= 0);
+            Assertions.assertNull(unexpectedException.get());
+
+            final PoolStats stats = pool.getStats(route);
+            Assertions.assertEquals(0, stats.getLeased());
+
+        } finally {
+            executorService.shutdownNow();
+            executorService.awaitTermination(TIMEOUT.getDuration(), TIMEOUT.getTimeUnit());
+            pool.close(CloseMode.GRACEFUL);
+        }
+    }
+}