hystrix 缓存 的作用是
- 1.减少重复的请求数，降低依赖服务的返回数据始终保持一致。
- 2.==在同一个用户请求的上下文中，相同依赖服务的返回数据始终保持一致==。
- 3.请求缓存在run()和construct()执行之前生效，所以可以有效减少不必要的线程开销。
1 通过hystrixcommand类实现
1.1 开启缓存功能
继承hystrixcommand或hystrixobservablecommand，覆盖getcachekey()方法，指定缓存的key，开启缓存配置。
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import com.netflix.hystrix.hystrixcommand; import com.netflix.hystrix.hystrixcommandgroupkey; import com.netflix.hystrix.hystrixcommandkey; import com.netflix.hystrix.hystrixrequestcache; import com.netflix.hystrix.strategy.concurrency.hystrixconcurrencystrategydefault; import com.szss.demo.orders.vo.uservo; import org.slf4j.logger; import org.slf4j.loggerfactory; import org. spring framework.web.client.resttemplate;
public class usercachecommand extends hystrixcommand<uservo> { private static final logger logger = loggerfactory.getlogger(usercachecommand. class );
private static final hystrixcommandkey getter_key= hystrixcommandkey.factory.askey( "commandkey" ); private resttemplate resttemplate; private string username;
public usercachecommand(resttemplate resttemplate, string username) { super (setter.withgroupkey(hystrixcommandgroupkey.factory.askey( "usercachecommand" )).andcommandkey(getter_key)); this .resttemplate = resttemplate; this .username = username; }
@override protected uservo run() throws exception { logger.info( "thread:" + thread.currentthread().getname()); return resttemplate.getforobject( "http://users-service/user/name/{username}" , uservo. class , username); }
@override protected uservo getfallback() { uservo user = new uservo(); user.setid(-1l); user.setusername( "调用失败" ); return user; }
@override protected string getcachekey() { return username; }
public static void flushcache(string username){ hystrixrequestcache.getinstance(getter_key, hystrixconcurrencystrategydefault.getinstance()).clear(username); } } |
1.2 配置hystrixrequestcontextservletfilter
通过servlet的filter配置hystrix的上下文。
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import com.netflix.hystrix.strategy.concurrency.hystrixrequestcontext; import javax.servlet.*; import javax.servlet.annotation.webfilter; import java.io.ioexception;
@webfilter (filtername = "hystrixrequestcontextservletfilter" ,urlpatterns = "/*" ,asyncsupported = true ) public class hystrixrequestcontextservletfilter implements filter { public void dofilter(servletrequest request, servletresponse response, filterchain chain) throws ioexception, servletexception { hystrixrequestcontext context = hystrixrequestcontext.initializecontext(); try { chain.dofilter(request, response); } finally { context.shutdown(); } }
@override public void init(filterconfig filterconfig) throws servletexception {
}
@override public void destroy() {
} } |
在不同context中的缓存是不共享的，还有这个request内部一个threadlocal，所以request只能限于当前线程。
1.3 清除失效缓存
继承hystrixcommand或hystrixobservablecommand，在更新接口调用完成后，清空缓存。
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import com.netflix.hystrix.hystrixcommand; import com.netflix.hystrix.hystrixcommandgroupkey; import com.netflix.hystrix.hystrixcommandkey; import com.szss.demo.orders.vo.uservo; import org.slf4j.logger; import org.slf4j.loggerfactory; import org.springframework.http.httpentity; import org.springframework.web.client.resttemplate;
public class userupdatecachecommand extends hystrixcommand<uservo> { private static final logger logger = loggerfactory.getlogger(userupdatecachecommand. class );
private static final hystrixcommandkey getter_key = hystrixcommandkey.factory.askey( "commandkey" ); private resttemplate resttemplate; private uservo user;
public userupdatecachecommand(resttemplate resttemplate, uservo user) { super (setter.withgroupkey(hystrixcommandgroupkey.factory.askey( "userupdatecachecommand" ))); this .resttemplate = resttemplate; this .user = user; }
@override protected uservo run() throws exception { logger.info( "thread:" + thread.currentthread().getname()); httpentity<uservo> u = new httpentity<uservo>(user); uservo uservo=resttemplate.postforobject( "http://users-service/user" ,u,uservo. class ); usercachecommand.flushcache(user.getusername()); return uservo; }
// @override // protected uservo getfallback() { // uservo user = new uservo(); // user.setid(-1l); // user.setusername("调用失败"); // return user; // }
@override protected string getcachekey() { return user.getusername(); } } |
2 使用@cacheresult、@cacheremove和@cachekey标注来实现缓存
2.1 使用@cacheresult实现缓存功能
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@cacheresult (cachekeymethod = "getcachekey" ) @hystrixcommand (commandkey = "finduserbyid" , groupkey = "userservice" , threadpoolkey = "userservicethreadpool" ) public uservo findbyid( long id) { responseentity<uservo> user = resttemplate.getforentity( "http://users-service/user?id={id}" , uservo. class , id); return user.getbody(); }
public string getcachekey( long id) { return string.valueof(id); } |
@cacheresult注解中的cachekeymethod用来标示缓存key(cachekey)的生成函数。函数的名称可任意取名，入参和标注@cacheresult的方法是一致的，返回类型是string。
2.2 使用@cacheresult和@cachekey实现缓存功能
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@cacheresult @hystrixcommand (commandkey = "finduserbyid" , groupkey = "userservice" , threadpoolkey = "userservicethreadpool" ) public uservo findbyid2( @cachekey ( "id" ) long id) { responseentity<uservo> user = resttemplate.getforentity( "http://users-service/user?id={id}" , uservo. class , id); return user.getbody(); } |
标注@hystrixcommand注解的方法，使用@cachekey标注需要指定的参数作为缓存key。
2.3 使用@cacheremove清空缓存
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@cacheremove (commandkey = "finduserbyid" ) @hystrixcommand (commandkey = "updateuser" ,groupkey = "userservice" ,threadpoolkey = "userservicethreadpool" ) public void updateuser( @cachekey ( "id" )uservo user){ resttemplate.postforobject( "http://users-service/user" ,user,uservo. class ); } |
@cacheremove必须指定commandkey，否则程序无法找到缓存位置。
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。
原文链接：https://blog.csdn.net/zhuchuangang/article/details/74566185
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