[Java] Spring Cloud Gateway重试机制的实现

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

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);
  
  // .....
}

public enum series {
  informational(1),
  successful(2),
  redirection(3),
  client_error(4),
  server_error(5);
}

public enum httpmethod {
  get, head, post, put, patch, delete, options, trace;
}

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");
}

@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);
  };
}