使用Byteman和JUnit进行故障注入

我们的应用程序独立存在的时间已经很久了。如今，应用程序是一种非常复杂的野兽，它们使用无数的API和协议相互通信，将数据存储在传统或NoSQL数据库中，通过网络发送消息和事件……例如，如果考虑到数据库，您会多久考虑会发生什么？当您的应用程序正在主动查询时发生故障？还是某个API端点突然开始拒绝连接？将此类事故作为测试套件的一部分覆盖不是很好吗？这就是故障注入和Byteman框架所要解决的问题。例如，我们将构建一个现实的，功能完善的Spring应用程序，该应用程序使用Hibernate / JPA访问MySQL数据库并管理客户。作为应用程序的JUnit集成测试套件的一部分，我们将包括三种测试用例：

储存/寻找顾客
存储客户并尝试在数据库宕机时查询数据库（故障模拟）
存储客户和数据库查询超时（故障模拟）

在本地开发箱上运行应用程序只有两个先决条件：

MySQL服务器已安装并具有客户数据库
Oracle JDK已安装，并且JAVA_HOME环境变量指向它

话虽这么说，我们已经准备好出发了。首先，让我们描述我们的域模型，该域模型由具有ID和单个属性名称的单个Customer类组成。看起来很简单：

package com.example.spring.domain;import java.io.Serializable;import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;@Entity
@Table( name = "customers" )
public class Customer implements Serializable{private static final long serialVersionUID = 1L;@Id@GeneratedValue@Column(name = "id", unique = true, nullable = false)private long id;@Column(name = "name", nullable = false)private String name;public Customer() {}public Customer( final String name ) {this.name = name;}public long getId() {return this.id;}protected void setId( final long id ) {this.id = id;}public String getName() {return this.name;}public void setName( final String name ) {this.name = name;}
}

为简单起见，服务层与数据访问层混合在一起并直接调用数据库。这是我们的CustomerService实现：

package com.example.spring.services;import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;import com.example.spring.domain.Customer;@Service
public class CustomerService {@PersistenceContext private EntityManager entityManager;@Transactional( readOnly = true )public Customer find( long id ) {return this.entityManager.find( Customer.class, id );}@Transactional( readOnly = false )public Customer create( final String name ) {final Customer customer = new Customer( name );this.entityManager.persist(customer);return customer;}@Transactional( readOnly = false )public void deleteAll() {this.entityManager.createQuery( "delete from Customer" ).executeUpdate();}
}

最后， Spring应用程序上下文定义了数据源和事务管理器。这里需要注意的一点是：由于我们不会引入数据访问层（ @Repository ）类，为了使Spring正确执行异常转换，我们将PersistenceExceptionTranslationPostProcessor实例定义为后处理服务类（ @Service ）。其他一切都应该非常熟悉。

package com.example.spring.config;import java.util.Properties;import javax.sql.DataSource;import org.hibernate.dialect.MySQL5InnoDBDialect;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor;
import org.springframework.jdbc.datasource.DriverManagerDataSource;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.Database;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.stereotype.Service;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;import com.example.spring.services.CustomerService;@EnableTransactionManagement
@Configuration
@ComponentScan( basePackageClasses = CustomerService.class )
public class AppConfig {@Beanpublic PersistenceExceptionTranslationPostProcessor exceptionTranslationPostProcessor() {final PersistenceExceptionTranslationPostProcessor processor = new PersistenceExceptionTranslationPostProcessor();processor.setRepositoryAnnotationType( Service.class );return processor;}@Beanpublic HibernateJpaVendorAdapter hibernateJpaVendorAdapter() {final HibernateJpaVendorAdapter adapter = new HibernateJpaVendorAdapter();adapter.setDatabase( Database.MYSQL );adapter.setShowSql( false );return adapter;}@Beanpublic LocalContainerEntityManagerFactoryBean entityManager() throws Throwable {final LocalContainerEntityManagerFactoryBean entityManager = new LocalContainerEntityManagerFactoryBean();entityManager.setPersistenceUnitName( "customers" );entityManager.setDataSource( dataSource() );entityManager.setJpaVendorAdapter( hibernateJpaVendorAdapter() );final Properties properties = new Properties();properties.setProperty("hibernate.dialect", MySQL5InnoDBDialect.class.getName());properties.setProperty("hibernate.hbm2ddl.auto", "create-drop" );entityManager.setJpaProperties( properties );return entityManager;}@Beanpublic DataSource dataSource() {final DriverManagerDataSource dataSource = new DriverManagerDataSource();dataSource.setDriverClassName( com.mysql.jdbc.Driver.class.getName() );dataSource.setUrl( "jdbc:mysql://localhost/customers?enableQueryTimeouts=true" );dataSource.setUsername( "root" );dataSource.setPassword( "" );return dataSource;}@Beanpublic PlatformTransactionManager transactionManager() throws Throwable {return new JpaTransactionManager( this.entityManager().getObject() );}
}

现在，让我们添加一个简单的JUnit测试用例，以验证我们的Spring应用程序确实按预期工作。在此之前，应创建数据库客户：

> mysql -u root
mysql> create database customers;
Query OK, 1 row affected (0.00 sec)

这是一个CustomerServiceTestCase ，目前，它具有用于创建客户并验证其是否已创建的单个测试。

package com.example.spring;import static org.hamcrest.CoreMatchers.notNullValue;
import static org.junit.Assert.assertThat;import javax.inject.Inject;import org.junit.After;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.support.AnnotationConfigContextLoader;import com.example.spring.config.AppConfig;
import com.example.spring.domain.Customer;
import com.example.spring.services.CustomerService;@RunWith( SpringJUnit4ClassRunner.class )
@ContextConfiguration(loader = AnnotationConfigContextLoader.class, classes = { AppConfig.class } )
public class CustomerServiceTestCase {@Inject private CustomerService customerService; @Afterpublic void tearDown() {customerService.deleteAll();}@Testpublic void testCreateCustomerAndVerifyItHasBeenCreated() throws Exception {Customer customer = customerService.create( "Customer A" );assertThat( customerService.find( customer.getId() ), notNullValue() );}
}

看起来很简单明了。现在，让我们考虑成功创建客户但由于查询超时而导致查找失败的情况。为此，我们需要Byteman的帮助。简而言之， Byteman是字节码操作框架。这是一个Java代理实现，可与JVM一起运行（或附加到JVM）并修改正在运行的应用程序字节码，从而改变其行为。 Byteman有一个很好的文档，并且拥有丰富的规则定义集，可以执行大多数开发人员可以想到的一切。而且，它与JUnit框架具有很好的集成。在该主题上，应该使用@RunWith（BMUnitRunner.class）运行Byteman测试，但是我们已经使用@RunWith（SpringJUnit4ClassRunner.class），并且JUnit不允许指定多个测试运行程序。除非您熟悉JUnit @Rule机制，否则这似乎是一个问题。事实证明，将BMUnitRunner转换为JUnit规则非常简单：

package com.example.spring;import org.jboss.byteman.contrib.bmunit.BMUnitRunner;
import org.junit.rules.MethodRule;
import org.junit.runners.model.FrameworkMethod;
import org.junit.runners.model.InitializationError;
import org.junit.runners.model.Statement;public class BytemanRule extends BMUnitRunner implements MethodRule {public static BytemanRule create( Class< ? > klass ) {try {return new BytemanRule( klass ); } catch( InitializationError ex ) { throw new RuntimeException( ex ); }}private BytemanRule( Class klass ) throws InitializationError {super( klass );}@Overridepublic Statement apply( final Statement statement, final FrameworkMethod method, final Object target ) {Statement result = addMethodMultiRuleLoader( statement, method ); if( result == statement ) {result = addMethodSingleRuleLoader( statement, method );}return result;}
}

JUnit @Rule注入就这么简单：

@Rule public BytemanRule byteman = BytemanRule.create( CustomerServiceTestCase.class );

容易吧？我们前面提到的场景可以改写一下：当执行从“客户”表中选择的JDBC语句执行时，我们应该因超时异常而失败。这是带有附加Byteman批注的JUnit测试用例的外观：

@Test( expected = DataAccessException.class )@BMRule(name = "introduce timeout while accessing MySQL database",targetClass = "com.mysql.jdbc.PreparedStatement",targetMethod = "executeQuery",targetLocation = "AT ENTRY",condition = "$0.originalSql.startsWith( \"select\" ) && !flagged( \"timeout\" )",action = "flag( \"timeout\" ); throw new com.mysql.jdbc.exceptions.MySQLTimeoutException( \"Statement timed out (simulated)\" )")public void testCreateCustomerWhileDatabaseIsTimingOut()  {Customer customer = customerService.create( "Customer A" );customerService.find( customer.getId() );}

我们可以这样写：“当有人调用PreparedStatement类的executeQuery方法并且查询以'SELECT'开始时，将抛出MySQLTimeoutException ，并且它应该只发生一次（由超时标志控制）”。运行此测试用例将在控制台中打印stacktrace，并期望引发DataAccessException ：

com.mysql.jdbc.exceptions.MySQLTimeoutException: Statement timed out (simulated)at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.7.0_21]at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) ~[na:1.7.0_21]at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.7.0_21]at java.lang.reflect.Constructor.newInstance(Constructor.java:525) ~[na:1.7.0_21]at org.jboss.byteman.rule.expression.ThrowExpression.interpret(ThrowExpression.java:231) ~[na:na]at org.jboss.byteman.rule.Action.interpret(Action.java:144) ~[na:na]at org.jboss.byteman.rule.helper.InterpretedHelper.fire(InterpretedHelper.java:169) ~[na:na]at org.jboss.byteman.rule.helper.InterpretedHelper.execute0(InterpretedHelper.java:137) ~[na:na]at org.jboss.byteman.rule.helper.InterpretedHelper.execute(InterpretedHelper.java:100) ~[na:na]at org.jboss.byteman.rule.Rule.execute(Rule.java:682) ~[na:na]at org.jboss.byteman.rule.Rule.execute(Rule.java:651) ~[na:na]at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java) ~[mysql-connector-java-5.1.24.jar:na]at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:56) ~[hibernate-core-4.2.0.Final.jar:4.2.0.Final]at org.hibernate.loader.Loader.getResultSet(Loader.java:2031) [hibernate-core-4.2.0.Final.jar:4.2.0.Final]

看起来不错，还有另一种情况：创建客户成功但由于数据库关闭而导致查找失败？这一点比较复杂，但无论如何都很容易做，让我们看一下：

@Test( expected = CannotCreateTransactionException.class )
@BMRules(rules = {@BMRule(name="create countDown for AbstractPlainSocketImpl",targetClass = "java.net.AbstractPlainSocketImpl",targetMethod = "getOutputStream",condition = "$0.port==3306",action = "createCountDown( \"connection\", 1 )"),@BMRule(name = "throw IOException when trying to execute 2nd query to MySQL",targetClass = "java.net.AbstractPlainSocketImpl",targetMethod = "getOutputStream",condition = "$0.port==3306 && countDown( \"connection\" )",action = "throw new java.io.IOException( \"Connection refused (simulated)\" )")}
)
public void testCreateCustomerAndTryToFindItWhenDatabaseIsDown() {Customer customer = customerService.create( "Customer A" );customerService.find( customer.getId() );
}

让我解释一下这是怎么回事。我们希望坐在套接字级别，并且实际上控制通讯尽可能地接近网络，而不是在JDBC驱动程序级别。这就是为什么我们要检测AbstractPlainSocketImpl的原因。我们也知道MySQL的默认端口是3306，因此我们仅检测在此端口上打开的套接字。另一个事实，我们知道第一个创建的套接字与客户创建相对应，我们应该让它通过。但是第二个对应于查找并且必须失败。名为“ connection”的createCountDown达到了此目的：第一次调用通过（闩锁尚未计数为零），但是第二个调用触发MySQLTimeoutException异常。运行此测试用例将在控制台中打印stacktrace，并期望抛出CannotCreateTransactionException ：

Caused by: java.io.IOException: Connection refused (simulated)at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.7.0_21]at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) ~[na:1.7.0_21]at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.7.0_21]at java.lang.reflect.Constructor.newInstance(Constructor.java:525) ~[na:1.7.0_21]at org.jboss.byteman.rule.expression.ThrowExpression.interpret(ThrowExpression.java:231) ~[na:na]at org.jboss.byteman.rule.Action.interpret(Action.java:144) ~[na:na]at org.jboss.byteman.rule.helper.InterpretedHelper.fire(InterpretedHelper.java:169) ~[na:na]at org.jboss.byteman.rule.helper.InterpretedHelper.execute0(InterpretedHelper.java:137) ~[na:na]at org.jboss.byteman.rule.helper.InterpretedHelper.execute(InterpretedHelper.java:100) ~[na:na]at org.jboss.byteman.rule.Rule.execute(Rule.java:682) ~[na:na]at org.jboss.byteman.rule.Rule.execute(Rule.java:651) ~[na:na]at java.net.AbstractPlainSocketImpl.getOutputStream(AbstractPlainSocketImpl.java) ~[na:1.7.0_21]at java.net.PlainSocketImpl.getOutputStream(PlainSocketImpl.java:214) ~[na:1.7.0_21]at java.net.Socket$3.run(Socket.java:915) ~[na:1.7.0_21]at java.net.Socket$3.run(Socket.java:913) ~[na:1.7.0_21]at java.security.AccessController.doPrivileged(Native Method) ~[na:1.7.0_21]at java.net.Socket.getOutputStream(Socket.java:912) ~[na:1.7.0_21]at com.mysql.jdbc.MysqlIO.(MysqlIO.java:330) ~[mysql-connector-java-5.1.24.jar:na]

大！字节曼为不同故障仿真提供的可能性是巨大的。仔细添加测试套件，以验证应用程序如何对错误的条件做出反应，从而大大提高了应用程序的健壮性和对故障的适应能力。多亏了Byteman伙计们！请在GitHub上找到完整的项目。

参考： 使用Byteman和JUnit进行故障注入：通过Andriy Redko {devmind}博客上的JCG合作伙伴 Andrey Redko，可以做更多的工作来确保应用程序的健壮性。