如何纠正一个asynchronous程序的结构，以确保正确的结果？

我有一个nodejs程序，请求一系列XML文件，parsing它们，然后将输出放入一个数组，该数组作为CSV文件写入磁盘。

该程序主要工作，但偶尔文件结束在arrays中错误的顺序。

我希望结果的顺序与URL的顺序相同。 这些URL存储在一个数组中，所以当我得到XML文件时，我会检查源数组中的URL索引，并将结果插入目标URL中的相同索引处。

任何人都可以看到允许结果以错误的顺序结束的缺陷？

addResult = function (url, value, timestamp) { data[config.sources.indexOf(url)] = { value : value, timestamp : timestamp, url : url }; numResults++; if (numResults === config.sources.length) { //once all results are in build the output file createOutputData(); } } fs.readFile("config.json", function (fileError, data) { var eachSource, processResponse = function (responseError, response, body) { if (responseError) { console.log(responseError); } else { parseXML(body, { explicitArray : false }, function (xmlError, result) { if (xmlError) { console.log(xmlError); } addResult(response.request.uri.href, result.Hilltop.Measurement.Data.E.I1, moment(result.Hilltop.Measurement.Data.ET)); }); } }; if (fileError) { console.log(fileError); } else { config = JSON.parse(data); //read in config file for (eachSource = 0; eachSource < config.sources.length; eachSource++) { config.sources[eachSource] = config.sources[eachSource].replace(/ /g, "%20"); //replace all %20 with " " request(config.sources[eachSource], processResponse); //request each source } } }); var writeOutputData, createOutputData, numResults = 0, data = [], eachDataPoint, multipliedFlow = 0; writeOutputData = function (output, attempts) { csv.writeToPath(config.outputFile, [ output ], { headers : false }).on("finish", function () { console.log("successfully wrote data to: ", config.outputFile); }).on("error", function (err) { //on write error console.log(err); if (attempts < 2) { //if there has been less than 3 attempts try writing again after 500ms setTimeout(function () { writeOutputData(output, attempts + 1); }, 500); } }); }; createOutputData = function () { var csvTimestamp, output = []; if (config.hasOwnProperty("timestampFromSource")) { csvTimestamp = data.filter(function (a) { return a.url === config.sources[config.timestampFromSource]; })[0].timestamp.format("HHmm"); console.log("timestamp from source [" + config.timestampFromSource + "]:", csvTimestamp); } else { csvTimestamp = data.sort(function (a, b) { //sort results from oldest to newest return a.timestamp.unix() - b.timestamp.unix(); }); csvTimestamp = csvTimestamp[0].timestamp.format("HHmm");//use the oldest date for the timestamp console.log("timestamp from oldest source:", csvTimestamp); } //build array to represent data to be written output.push(config.plDestVar); //pl var head address first output.push(config.sources.length + 1); //number if vars to import output.push(csvTimestamp); //the date of the data for (eachDataPoint = 0; eachDataPoint < data.length; eachDataPoint++) { //add each data point if (config.flowMultiplier) { multipliedFlow = Math.round(data[eachDataPoint].value * config.flowMultiplier); //round to 1dp and remove decimal by *10 } else { multipliedFlow = Math.round(data[eachDataPoint].value * 10); //round to 1dp and remove decimal by *10 } if (multipliedFlow > 32766) { multipliedFlow = 32766; } else if (multipliedFlow < 0) { multipliedFlow = 0; } output.push(multipliedFlow); } console.log(output); writeOutputData(output, 0); //write the results, 0 is signalling first attempt }; 

Answer 1

我同意@Kevin B，你不能假定asynchronouscallback将以你发送它们的相同顺序返回。 但是，您可以通过在processResponse上添加一个索引函数来确保顺序。

说你添加以下addResult

 addResult = function (index, url, value, timestamp) { data[index] = { value : value, timestamp : timestamp, url : url }; numResults++; if (numResults === config.sources.length) { //once all results are in build the output file createOutputData(); } } 

并使用额外的function来调用您的请求

 function doRequest(index, url) { request(url, function(responseError, response, body) { if (responseError) { console.log(responseError); } else { parseXML(body, { explicitArray : false }, function (xmlError, result) { if (xmlError) { console.log(xmlError); } addResult(index, response.request.uri.href, result.Hilltop.Measurement.Data.E.I1, moment(result.Hilltop.Measurement.Data.ET)); }); } }); } 

那么你也可以改变你的循环：

  for (eachSource = 0; eachSource < config.sources.length; eachSource++) { config.sources[eachSource] = config.sources[eachSource].replace(/ /g, "%20"); //replace all %20 with " " doRequest(eachSource, config.sources[eachSource]); //request each source } 

Answer 2

我认为，索引代码的url需要debugging。 下面是一个使用for循环中的键预填充对象的示例。

`

 var http = require('http'); var fs = require("fs"); var allRequestsComplete = function(results){ console.log("All Requests Complete"); console.log(results); }; fs.readFile("urls.json", function (fileError, data) { var responseCount = 0; if (fileError) { console.log(fileError); } else { var allResponses = {}; config = JSON.parse(data); //read in config file var requestComplete = function(url, fileData){ responseCount++; allResponses[url] = fileData; if(responseCount===config.sources.length){ allRequestsComplete(allResponses); } }; for (var eachSource = 0; eachSource < config.sources.length; eachSource++) { (function(url){ allResponses[url] = "Waiting"; http.get({host: url,path: "/"}, function(response) { response.on('error', function (chunk) { requestComplete(url, "ERROR"); }); var str = '' response.on('data', function (chunk) { str += chunk; }); response.on('end', function () { requestComplete(url, str); }); }); }(config.sources[eachSource].replace(/ /g, "%20").replace("http://", ""))); } } }); 

`