同步运行构建

Question

我的 for 循环无法同步运行。它为每个域返回的注册顺序发生了变化。我猜哪个答案最快的都会先带来这些记录。我哪里做错了？

const rrtypes= ["A","MX","CNAME","NS","TXT"];
var resData = [];
    
export const getAllRecords = async (req,res) => {
    const {domain} = req.params;
         for await(const rrtype of rrtypes){
             dns.resolve (domain, rrtype, (err, records) => { 
             resData.push(rrtype+" "+records);
        });
    }    
        res.send(resData);
        resData = [];      
}

Answer 1

注意可以使用dns.promises.resolve函数：https://nodejs.org/api/dns.html#dns_dnspromises_resolve_hostname_rrtype

因此您将代码更改为：

const rrtypes = ["A", "MX", "CNAME", "NS", "TXT"];

export const getAllRecords = async (req, res) => {
  const { domain } = req.params;

  // Notice that resData should be local to this function
  let resData = [];
  for (const rrtype of rrtypes) {
    try {
      const records = await dns.promises.resolve(domain, rrtype);
      resData.push(rrtype + " " + records);
      // IMO this would be better: resData.push({ type: rrtype, value: records });
    } catch (err) {
      // Log the error here
    }
  }

  res.send(resData);
};

Answer 2

问题在于您使用await。调用异步函数时应使用await。目前，您在从数组中实例化变量时使用它。

感谢 slebetman 的评论，我能够看到 dns.resolve 没有返回承诺，而是使用回调来管理异步调用。正如他还建议的那样，我们可以通过创建一个管理这些回调的承诺来解决这个问题。

const rrtypes= ["A","MX","CNAME","NS","TXT"];
var resData = [];

const dnsResolvePromise = (domain, rrtype) => {
  return new Promise((resolve, reject) => {
    dns.resolve(domain, rrtype, (err, records) => { 
        if(err) return reject(err);
        resolve(rrtype+" "+records);
    });
  })
}

export const getAllRecords = async (req,res) => {
    const {domain} = req.params;
    for(const rrtype of rrtypes){
        try{
            const records = await dnsResolvePromise(domain, rrtype);
            resData.push(records);
       } catch (e){
         // Handle error
       }
    }    
    res.send(resData);
    resData = [];      
}