前言
重试,我相信大家并不陌生。在我们调用http接口的时候,总会因为某种原因调用失败,这个时候我们可以通过重试的方式,来重新请求接口。
生活中这样的事例很多,比如打电话,对方正在通话中啊,信号不好啊等等原因,你总会打不通,当你第一次没打通之后,你会打第二次,第三次...第四次就通了。
重试也要注意应用场景,读数据的接口比较适合重试的场景,写数据的接口就需要注意接口的幂等性了。还有就是重试次数如果太多的话会导致请求量加倍,给后端造成更大的压力,设置合理的重试机制才是最关键的。
今天我们来简单的了解下spring cloud gateway中的重试机制和使用。
使用讲解
retrygatewayfilter是spring cloud gateway对请求重试提供的一个gatewayfilter factory。
配置方式:
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spring: cloud: gateway: routes: - id: fsh-house uri: lb: //fsh-house predicates: - path=/house/** filters: - name: retry args: retries: 3 series: - server_error statuses: - ok methods: - get - post exceptions: - java.io.ioexception |
配置讲解
配置类源码org.springframework.cloud.gateway.filter.factory.retrygatewayfilterfactory.retryconfig:
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public static class retryconfig { private int retries = 3 ; private list<series> series = tolist(series.server_error); private list<httpstatus> statuses = new arraylist<>(); private list<httpmethod> methods = tolist(httpmethod.get); private list< class <? extends throwable>> exceptions = tolist(ioexception. class ); // ..... } |
retries:重试次数,默认值是3次
series:状态码配置(分段),符合的某段状态码才会进行重试逻辑,默认值是server_error,值是5,也就是5xx(5开头的状态码),共有5个值:
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public enum series { informational( 1 ), successful( 2 ), redirection( 3 ), client_error( 4 ), server_error( 5 ); } |
statuses:状态码配置,和series不同的是这边是具体状态码的配置,取值请参考:org.springframework.http.httpstatus
methods:指定哪些方法的请求需要进行重试逻辑,默认值是get方法,取值如下:
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public enum httpmethod { get, head, post, put, patch, delete, options, trace; } |
exceptions:指定哪些异常需要进行重试逻辑,默认值是java.io.ioexception
代码测试
就写个接口,在接口中记录请求次数,然后抛出一个异常模拟500,通过网关访问这个接口,如果你配置了重试次数是3,那么接口中会输出4次结果才是对的,证明重试生效了。
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atomicinteger ac = new atomicinteger(); @getmapping ( "/data" ) public houseinfo getdata( @requestparam ( "name" ) string name) { if (stringutils.isblank(name)) { throw new runtimeexception( "error" ); } system.err.println(ac.addandget( 1 )); return new houseinfo(1l, "上海" , "虹口" , "xx小区" ); } |
更多spring cloud代码尽在:https://github.com/yinjihuan/spring-cloud
源码欣赏
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@override public gatewayfilter apply(retryconfig retryconfig) { // 验证重试配置格式是否正确 retryconfig.validate(); repeat<serverwebexchange> statuscoderepeat = null ; if (!retryconfig.getstatuses().isempty() || !retryconfig.getseries().isempty()) { predicate<repeatcontext<serverwebexchange>> repeatpredicate = context -> { serverwebexchange exchange = context.applicationcontext(); // 判断重试次数是否已经达到了配置的最大值 if (exceedsmaxiterations(exchange, retryconfig)) { return false ; } // 获取响应的状态码 httpstatus statuscode = exchange.getresponse().getstatuscode(); // 获取请求方法类型 httpmethod httpmethod = exchange.getrequest().getmethod(); // 判断响应状态码是否在配置中存在 boolean retryablestatuscode = retryconfig.getstatuses().contains(statuscode); if (!retryablestatuscode && statuscode != null ) { // null status code might mean a network exception? // try the series retryablestatuscode = retryconfig.getseries().stream() .anymatch(series -> statuscode.series().equals(series)); } // 判断方法是否包含在配置中 boolean retryablemethod = retryconfig.getmethods().contains(httpmethod); // 决定是否要进行重试 return retryablemethod && retryablestatuscode; }; statuscoderepeat = repeat.onlyif(repeatpredicate) .doonrepeat(context -> reset(context.applicationcontext())); } //todo: support timeout, backoff, jitter, etc... in builder retry<serverwebexchange> exceptionretry = null ; if (!retryconfig.getexceptions().isempty()) { predicate<retrycontext<serverwebexchange>> retrycontextpredicate = context -> { if (exceedsmaxiterations(context.applicationcontext(), retryconfig)) { return false ; } // 异常判断 for ( class <? extends throwable> clazz : retryconfig.getexceptions()) { if (clazz.isinstance(context.exception())) { return true ; } } return false ; }; // 使用reactor extra的retry组件 exceptionretry = retry.onlyif(retrycontextpredicate) .doonretry(context -> reset(context.applicationcontext())) .retrymax(retryconfig.getretries()); } return apply(statuscoderepeat, exceptionretry); } public boolean exceedsmaxiterations(serverwebexchange exchange, retryconfig retryconfig) { integer iteration = exchange.getattribute(retry_iteration_key); //todo: deal with null iteration return iteration != null && iteration >= retryconfig.getretries(); } public void reset(serverwebexchange exchange) { //todo: what else to do to reset swe? exchange.getattributes().remove(serverwebexchangeutils.gateway_already_routed_attr); } public gatewayfilter apply(repeat<serverwebexchange> repeat, retry<serverwebexchange> retry) { return (exchange, chain) -> { if (log.istraceenabled()) { log.trace( "entering retry-filter" ); } // chain.filter returns a mono<void> publisher< void > publisher = chain.filter(exchange) //.log("retry-filter", level.info) .doonsuccessorerror((avoid, throwable) -> { // 获取已经重试的次数,默认值为-1 int iteration = exchange.getattributeordefault(retry_iteration_key, - 1 ); // 增加重试次数 exchange.getattributes().put(retry_iteration_key, iteration + 1 ); }); if (retry != null ) { // retrywhen returns a mono<void> // retry needs to go before repeat publisher = ((mono< void >)publisher).retrywhen(retry.withapplicationcontext(exchange)); } if (repeat != null ) { // repeatwhen returns a flux<void> // so this needs to be last and the variable a publisher<void> publisher = ((mono< void >)publisher).repeatwhen(repeat.withapplicationcontext(exchange)); } return mono.fromdirect(publisher); }; } |
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服务器之家。
原文链接:https://segmentfault.com/a/1190000018469096