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Spring Cloud杜绝循环依赖

前言

大家在开发中有没有遇到过因循环依赖导致项目启动失败?在排查循环依赖的过程中有没困难?如何避免写出循环依赖的代码?

我没写过循环依赖的代码,作为稳定性负责人,我排查过多次。

有些逻辑简单的代码,循环依赖很容易排查。但是,我们的业务超级复杂,绝大多数循环依赖,一整天都查不出来。

起初我们遇到一个循环依赖处理一个,作为稳定性负责人,技术能干的事,不会让人做第二次,为此,我写了一段循环依赖巡检代码,把循环依赖扼杀在测试环境。

 

下面介绍下场景及处理思路,未必最优,欢迎交流。

背景

SpringCloud服务在上线时出现BeanCurrentlyInCreationException异常(服务本地启动无异常,测试环境启动也无异常,上线就偶尔异常)。

1,本地模拟如下:

Caused by: org.springframework.beans.factory.BeanCurrentlyInCreationException:
Error creating bean with name  'studentA' : Bean with name  'studentA'  has been injected into other beans [studentC] in its raw version as part of a circular reference, but has eventually been wrapped.
This means that said other beans  do  not use the  final  version of the bean.
This is often the result of over-eager type matching - consider using  'getBeanNamesOfType'  with the  'allowEagerInit'  flag turned off,  for  example.
 

2,生产场景如下图:

 

异常排查&模拟

 经过生产排查和本地测试,产生此异常的场景如下:

1,如果类方法有@Async注解,则可能出现如上异常

2,如果存在循环依赖,并且类方法上有@Async注解,则必然会出现如上异常。

1,场景演示:

 在spring中,基于field属性的循环依赖是可以的:

 

示例代码:

@Service
@Slf4j
public class StudentA {

    @Autowired
    private StudentB studentB;
    public String test(){
        return studentB.test();
    }
    public String test1(){
        return "Studenta1";
    }
}

@Slf4j
@Service
public class StudentB {

    @Autowired
    private StudentC studentC;

    public String test() {
        return "Studentb";
    }

    public String test1() {
        return studentC.test1();
    }
}

@Slf4j
@Service
public class StudentC {

    @Autowired
    private StudentA studentA;

    public String test() {
        return studentA.test();
    }

    public String test1() {
        return "Studentc1";
    }
}

@Autowired
private StudentA studentA ;
@Test
public void testA(){
    String v= studentA.test();
    log.info("testa={}",v);
}

以上代码输出正常

2,异常演示

如果我们的方法加上了@Async 注解。则抛出异常:

@Service
@Slf4j
public class StudentA {

    @Autowired
    private StudentB studentB;
    @Async
    public String test(){
        return studentB.test();
    }
    @Async
    public String test1(){
        return "Studenta1";
    }
}

@Slf4j
@Service
public class StudentB {

    @Autowired
    private StudentC studentC;
    @Async
    public String test() {
        return "Studentb";
    }
    @Async
    public String test1() {
        return studentC.test1();
    }
}

@Slf4j
@Service
public class StudentC {

    @Autowired
    private StudentA studentA;
    @Async
    public String test() {
        return studentA.test();
    }
    @Async
    public String test1() {
        return "Studentc1";
    }
}

@Autowired
private StudentA studentA ;
@Test
public void testA(){
    String v= studentA.test();
    log.info("testa={}",v);
}
Caused by: org.springframework.beans.factory.BeanCurrentlyInCreationException: 
Error creating bean with name 'studentA': Bean with name 'studentA' has been injected into other beans [studentC] in its raw version as part of a circular reference, but has eventually been wrapped. 
This means that said other beans do not use the final version of the bean. 
This is often the result of over-eager type matching - consider using 'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.

3,解决异常

A,B,C三个类中,至少一个类的field 必须加@Lazy  

@Service
@Slf4j
public class StudentA {

    @Autowired
    @Lazy
    private StudentB studentB;
    @Async
    public String test(){
        return studentB.test();
    }
    @Async
    public String test1(){
        return "Studenta1";
    }
}

@Slf4j
@Service
public class StudentB {

    @Autowired
    @Lazy
    private StudentC studentC;
    @Async
    public String test() {
        return "Studentb";
    }
    @Async
    public String test1() {
        return studentC.test1();
    }
}

@Slf4j
@Service
public class StudentC {

    @Autowired
    @Lazy
    private StudentA studentA;
    @Async
    public String test() {
        return studentA.test();
    }
    @Async
    public String test1() {
        return "Studentc1";
    }
}

参考 :https://my.oschina.net/tridays/blog/805111 

杜绝循环依赖的解决方案

这里根据我司的服务架构介绍一下如何避免循环依赖,我司用的spring cloud 全家桶,注册中心用的consul,配置中心有config 和apollo。

1,查看bean的依赖

spring-cloud 提供了bean信息查看功能,通过ip:端口+/actuator/beans可查看(如何配置actuator这里不详细讨论),如下图,我们可以看到每个bean依赖的bean
 

  

2,解析bean及其依赖beans

如上,我们可以查看某个bean的依赖项,由此,我们可以递归查找bean是否存在循环引用。

bean 信息模型

@Data
public class ApplicationBeans {

    private Map<String, ContextBeans> contexts;
}



@Data
public class ContextBeans {

    private Map<String, BeanDescriptor> beans;
    private String parentId;
}

 

 3,代码实现

这里检测项目起名alarm-center,检测类为CheckCyclicDependenceService 

@Slf4j
@RefreshScope
@Service
public class CheckCyclicDependenceService {

// 服务发现 @Autowired
private DiscoveryClient discoveryClient;
//默认检测 api,admin两个项目,如果想检测其它项目,可在config配置 @Value(
"${check-serviceids-value:api,admin}") private String checkServiceIds;

//入口
public void checkCyclicDependence() { if (Strings.isNullOrEmpty(checkServiceIds)) { return; } List<String> serviceIds = Arrays.asList(checkServiceIds.split(",")); for (String serviceId : serviceIds) { long start = System.currentTimeMillis(); RestTemplate restTemplate = new RestTemplate();
//根据服务名去consul找一个服务实例 ServiceInstance instance
= discoveryClient.getInstances(serviceId).get(0); String url = instance.getUri() + "/actuator/beans"; //所有的beans信息 String applicationBeansStr = restTemplate.getForObject(url, String.class); ApplicationBeans applicationBeans = JSONObject.parseObject(applicationBeansStr, ApplicationBeans.class); long end = System.currentTimeMillis(); log.info("checkCyclicDependence get applicationBeans end,serviceid={},coust={}", serviceId, (end - start)); Map<String, ContextBeans> contexts = applicationBeans.getContexts(); Map<String, BeanDescriptor> qualifiedBeans = new HashMap<>(); for (Map.Entry<String, ContextBeans> conEntry : contexts.entrySet()) { if (!conEntry.getKey().startsWith(serviceId)) { continue; } ContextBeans contextBeans = conEntry.getValue(); Map<String, BeanDescriptor> beans = contextBeans.getBeans(); for (Map.Entry<String, BeanDescriptor> entry1 : beans.entrySet()) { String beanName = entry1.getKey().toLowerCase(); BeanDescriptor beanDescriptor = entry1.getValue(); if (!beanDescriptor.getType().startsWith("com.shuidihuzhu") || beanName.endsWith("aspect") || beanName.endsWith("controller") || beanName.endsWith("dao") || beanName.endsWith("datasource") || beanName.endsWith("fallback") || beanDescriptor.getDependencies().length == 0) { continue; } qualifiedBeans.put(entry1.getKey(), beanDescriptor); } } StringBuilder sb = new StringBuilder(); cyclicDependence(qualifiedBeans, sb); if (sb.length() > 0) { sb.append(System.getProperty("line.separator")); sb.append("重注代码质量,尽量做到无循环依赖"); sb.append(System.getProperty("line.separator")); sb.append("所属服务:" + serviceId); //alarmClient.sendByUser(Lists.newArrayList("zhangzhi"), sb.toString()); alarmClient.sendByGroup("cf-server-alarm", sb.toString()); end = System.currentTimeMillis(); } log.info("checkCyclicDependence end,serviceid={},coust={}", serviceId, (end - start)); } } public void cyclicDependence(Map<String, BeanDescriptor> beans, StringBuilder sb) { for (Map.Entry<String, BeanDescriptor> bean : beans.entrySet()) { String beanName = bean.getKey(); check(beans, beanName, beanName, 0, sb); } } public void check(Map<String, BeanDescriptor> beans, String beanName, String dependenceName, int depth, StringBuilder sb) { if (depth == 4) {//这里可以指定深度,层级过多,容易栈溢出 return; } depth++; BeanDescriptor bean = beans.get(dependenceName);//依赖项的依赖项 if (bean != null) { String[] deps = bean.getDependencies();//依赖项 for (String dep : deps) { if (dep.equals(beanName)) { sb.append(System.getProperty("line.separator")); String str = String.format("%s和%s存在循环依赖;", beanName, dependenceName); sb.append(str); log.info(str); } else { check(beans, beanName, dep, depth, sb); } } } } }

 

效果

我们在测试环境有个job 每隔几分钟巡检,有循环依赖就企业微信报警,这里截取一段日志,如下:

 

最后

水滴保险商城-架构组招java实习生

要求:
1、具备较强的编程基本功,熟练掌握JAVA编程语言,熟悉常用数据结构与算法。
2、了解常用的开源框架和开源服务(Spring,Netty,MySQL,Redis,Tomcat,Nginx 等)。
3、熟悉网络编程、多线程编程、分布式等优先。
4、阅读过spring家族源码优先,有技术博客优先,熟悉spring-cloud技术栈优先。
5、 做事积极主动,有较强的执行能力和和较好的沟通能力。

 

 

版权声明
本文为[zzhi.wang]所创,转载请带上原文链接,感谢
https://www.cnblogs.com/zhangzhi19861216/p/13958124.html

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