DATAMONGO-585 - Fix concurrency issue in database authentication.

So far the authentication of the database was synchronized *after* the check whether the database under consideration had already been authenticated. This can cause threads to concurrently try to authenticate the database which is rejected by the driver. Improved the synchronization block to include both the ….isAuthenticated() check as well as the authentication.

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/MongoDbUtils.java

@@ -104,12 +104,13 @@ public abstract class MongoDbUtils {
 		DB db = mongo.getDB(databaseName);
 		boolean credentialsGiven = credentials.hasUsername() && credentials.hasPassword();
 
+		synchronized (db) {
+
 			if (credentialsGiven && !db.isAuthenticated()) {
 
 				String username = credentials.getUsername();
 				String password = credentials.hasPassword() ? credentials.getPassword() : null;
 
-			synchronized (db) {
 				if (!db.authenticate(username, password == null ? null : password.toCharArray())) {
 					throw new CannotGetMongoDbConnectionException("Failed to authenticate to database [" + databaseName
 							+ "], username = [" + username + "], password = [" + password + "]", databaseName, credentials);

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/MongoDbUtilsIntegrationTests.java

@@ -0,0 +1,124 @@
+/*
+ * Copyright 2012 the original author or authors.
+ *
+ * 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 org.springframework.data.mongodb.core;
+
+import static org.hamcrest.CoreMatchers.*;
+import static org.junit.Assert.*;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.springframework.dao.DataAccessException;
+import org.springframework.data.authentication.UserCredentials;
+import org.springframework.scheduling.concurrent.ThreadPoolExecutorFactoryBean;
+
+import com.mongodb.DB;
+import com.mongodb.Mongo;
+import com.mongodb.MongoException;
+
+/**
+ * Integration tests for {@link MongoDbUtils}.
+ * 
+ * @author Oliver Gierke
+ */
+public class MongoDbUtilsIntegrationTests {
+
+	static final String DATABASE_NAME = "dbAuthTests";
+	static final UserCredentials CREDENTIALS = new UserCredentials("admin", "admin");
+
+	static Mongo mongo;
+	static MongoTemplate template;
+	static ThreadPoolExecutorFactoryBean factory;
+	static ExecutorService service;
+
+	Exception exception;
+
+	@BeforeClass
+	public static void setUp() throws Exception {
+
+		mongo = new Mongo();
+		template = new MongoTemplate(mongo, DATABASE_NAME);
+
+		// Create sample user
+		template.execute(new DbCallback<Void>() {
+			public Void doInDB(DB db) throws MongoException, DataAccessException {
+				db.addUser("admin", "admin".toCharArray());
+				return null;
+			}
+		});
+
+		factory = new ThreadPoolExecutorFactoryBean();
+		factory.setCorePoolSize(2);
+		factory.setMaxPoolSize(10);
+		factory.setWaitForTasksToCompleteOnShutdown(true);
+		factory.afterPropertiesSet();
+
+		service = factory.getObject();
+	}
+
+	@AfterClass
+	public static void tearDown() {
+
+		factory.destroy();
+
+		// Remove test database
+
+		template.execute(new DbCallback<Void>() {
+			public Void doInDB(DB db) throws MongoException, DataAccessException {
+				db.dropDatabase();
+				return null;
+			}
+		});
+	}
+
+	/**
+	 * @see DATAMONGO-585
+	 */
+	@Test
+	public void authenticatesCorrectlyInMultithreadedEnvironment() throws Exception {
+
+		Callable<Void> callable = new Callable<Void>() {
+			public Void call() throws Exception {
+
+				try {
+					DB db = MongoDbUtils.getDB(mongo, DATABASE_NAME, CREDENTIALS);
+					assertThat(db, is(notNullValue()));
+				} catch (Exception o_O) {
+					MongoDbUtilsIntegrationTests.this.exception = o_O;
+				}
+
+				return null;
+			}
+		};
+
+		List<Callable<Void>> callables = new ArrayList<Callable<Void>>();
+
+		for (int i = 0; i < 10; i++) {
+			callables.add(callable);
+		}
+
+		service.invokeAll(callables);
+
+		if (exception != null) {
+			fail("Exception occurred!" + exception);
+		}
+	}
+}