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
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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 );
// .....
}
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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 );
}
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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;
}
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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" );
}
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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);
};
}
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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