JAVA-2052: Ensure that DefaultConnectionPool only used daemon background threads

Author: jyemin

driver-core/src/main/com/mongodb/connection/DefaultConnectionPool.java

@@ -31,6 +31,7 @@
 import com.mongodb.event.ConnectionPoolOpenedEvent;
 import com.mongodb.event.ConnectionPoolWaitQueueEvent;
 import com.mongodb.internal.connection.ConcurrentPool;
+import com.mongodb.internal.thread.DaemonThreadFactory;
 import org.bson.ByteBuf;
 
 import java.util.List;
@@ -49,6 +50,7 @@
 
 class DefaultConnectionPool implements ConnectionPool {
     private static final Logger LOGGER = Loggers.getLogger("connection");
+    private static final DaemonThreadFactory THREAD_FACTORY = new DaemonThreadFactory();
 
     private final ConcurrentPool<UsageTrackingInternalConnection> pool;
     private final ConnectionPoolSettings settings;
@@ -207,7 +209,7 @@ public void onResult(final Void result, final Throwable t) {
 
     private synchronized ExecutorService getAsyncGetter() {
         if (asyncGetter == null) {
-            asyncGetter = Executors.newSingleThreadExecutor();
+            asyncGetter = Executors.newSingleThreadExecutor(THREAD_FACTORY);
         }
         return asyncGetter;
     }
@@ -310,7 +312,7 @@ private ExecutorService createTimer() {
         if (maintenanceTask == null) {
             return null;
         } else {
-            ScheduledExecutorService newTimer = Executors.newSingleThreadScheduledExecutor();
+            ScheduledExecutorService newTimer = Executors.newSingleThreadScheduledExecutor(THREAD_FACTORY);
             newTimer.scheduleAtFixedRate(maintenanceTask, settings.getMaintenanceInitialDelay(MILLISECONDS),
                                          settings.getMaintenanceFrequency(MILLISECONDS), MILLISECONDS);
             return newTimer;

driver-core/src/main/com/mongodb/internal/thread/DaemonThreadFactory.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2015 MongoDB, Inc.
+ *
+ * Licensed 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.
+ *
+ */
+
+package com.mongodb.internal.thread;
+
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * Custom thread factory for scheduled executor service that creates daemon threads.  Otherwise,
+ * applications that neglect to close the client will not exit.
+ *
+ * <p>This class should not be considered a part of the public API.</p>
+ */
+public class DaemonThreadFactory implements ThreadFactory {
+    private static final AtomicInteger POOL_NUMBER = new AtomicInteger(1);
+    private final AtomicInteger threadNumber = new AtomicInteger(1);
+    private final String namePrefix;
+
+    public DaemonThreadFactory() {
+        this("pool");
+    }
+
+    public DaemonThreadFactory(final String prefix) {
+        namePrefix = prefix + "-" + POOL_NUMBER.getAndIncrement() + "-thread-";
+    }
+
+    @Override
+    public Thread newThread(final Runnable runnable) {
+        Thread t = new Thread(runnable, namePrefix + threadNumber.getAndIncrement());
+        t.setDaemon(true);
+        return t;
+    }
+}

driver-core/src/test/unit/com/mongodb/internal/thread/DaemonThreadFactorySpecification.groovy

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2015 MongoDB, Inc.
+ *
+ * Licensed 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.
+ *
+ */
+
+package com.mongodb.internal.thread
+
+import spock.lang.Specification
+
+class DaemonThreadFactorySpecification extends Specification {
+    def 'should create daemon threads'() {
+        def factory = new DaemonThreadFactory()
+
+        when:
+        def thread = factory.newThread { }
+
+        then:
+        thread.isDaemon()
+    }
+}

driver/src/main/com/mongodb/Mongo.java

@@ -35,6 +35,7 @@
 import com.mongodb.event.CommandListener;
 import com.mongodb.event.CommandListenerMulticaster;
 import com.mongodb.internal.connection.PowerOfTwoBufferPool;
+import com.mongodb.internal.thread.DaemonThreadFactory;
 import com.mongodb.management.JMXConnectionPoolListener;
 import com.mongodb.operation.CurrentOpOperation;
 import com.mongodb.operation.FsyncUnlockOperation;
@@ -56,8 +57,6 @@
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
-import java.util.concurrent.ThreadFactory;
-import java.util.concurrent.atomic.AtomicInteger;
 
 import static com.mongodb.ReadPreference.primary;
 import static com.mongodb.connection.ClusterConnectionMode.MULTIPLE;
@@ -897,22 +896,4 @@ private String toKey(final MongoClientURI uri) {
             return uri.toString();
         }
     }
-
-    // Custom thread factory for scheduled executor service that creates daemon threads.  Otherwise,
-    // applications that neglect to close MongoClient will not exit.
-    static class DaemonThreadFactory implements ThreadFactory {
-        private static final AtomicInteger poolNumber = new AtomicInteger(1);
-        private final AtomicInteger threadNumber = new AtomicInteger(1);
-        private final String namePrefix;
-
-        DaemonThreadFactory() {
-            namePrefix = "pool-" + poolNumber.getAndIncrement() + "-thread-";
-        }
-
-        public Thread newThread(final Runnable runnable) {
-            Thread t = new Thread(runnable, namePrefix + threadNumber.getAndIncrement());
-            t.setDaemon(true);
-            return t;
-        }
-    }
 }