发送后无法设置headers。节点快递

Question

我还有一个 "Can't set headers after they are sent." 问题。我创建了一个 post 路由器，它接收大量 object 的 url，我需要对其进行处理。

处理过程包括抓取 object 包含的所有网址。我设置了一个瓶颈，最大并发爬取10个，等待时间800毫秒。

无论哪种方式，数据都有可能到达并记录下来，但是当我调用我的函数（假设它处理数据）时，我的应用程序抛出异常。

Post 路由器

router.post('/crawledUrls', function (req, res, err) {
    crawler = new crawlerClass();
    var urlArray = JSON.parse(req.body);
    crawler.crawlArrayUrls(urlArray);
    res.send({message: "Array sent successfully!"});
});

crawler.crawlArrayUrls

crawlerClass.prototype.crawlArrayUrls = function (arrayObject) {
var itemsProcessed = 0;
var emptyUrlArray = [];
var newArray = [];
for(keys in arrayObject){
    newArray.push(arrayObject[keys]);
}
var limiter = new Bottleneck(10, 800);
newArray.forEach(function (listItem, indexArray, err) {
    limiter.submit(err, function () {
        if(err) throw err;
        request({
            encoding: null,
            method: "GET",
            headers: {
                'User-Agent': 'request'
            },
            uri: listItem
        }, function (error, response, body, err) {
            if(err) throw err;
            $ = cheerio.load(body);
            if($('div.alert.alert-danger').html() == undefined) {
                console.log(listItem);
                emptyUrlArray.push(listItem);
            } else {
                console.log("Else");
                //Not done.
            }
        });
    });
});

};

App.js

var express = require('express');
var session = require('express-session');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
//var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var scheduleObject = require('./UtilityLogic/scheduleObject');
var scheduleBidding = require("./GoogleAPILogic/scheduleBidding");
var dbModules = require("./DBLogic/dbModules");
var routes = require('./routes/index');

var app = express();

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');
app.enable('trust proxy');

app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));

app.use(session({
    secret: 'secret',
    resave: false,
    saveUninitialized: true,
    cookie: {
        httpOnly: true,
        secure: true
    }
}));
app.use(express.static(path.join(__dirname, 'public')));

app.use('/', routes);

// catch 404 and forward to error handler
app.use(function(req, res, next) {
  var err = new Error('Not Found');
  err.status = 404;
  next(err);
});

// error handlers

// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
  app.use(function(err, req, res, next) {
    res.status(err.status || 500);
    res.render('error', {
      message: err.message,
      error: err
    });
      throw err;
  });
}

// production error handler
// no stacktraces leaked to user
app.use(function(err, req, res, next) {
  res.status(err.status || 500);
  res.render('error', {
    message: err.message,
    error: {}
  });
});

var scheduler = new scheduleObject();
var dbObject = new dbModules("./somePath");
var scheduleBidObject = new scheduleBidding("someKey");

//Test connection to DB
dbObject.testConnectionToDB();

scheduler.scheduleFunction('59 59 23 * * *',function (){
    scheduleBidObject.getBiddingHeaders('/SomePath/');
});

scheduler.scheduleFunction('01  e 10 00 * * *',function (){
    scheduleBidObject.getBiddingHeaders('/SomePath/');
});

module.exports = app;

抛出异常

Error: Can't set headers after they are sent.
www-2     at ServerResponse.OutgoingMessage.setHeader (http.js:691:11)
www-2     at ServerResponse.header (/somePath/node_modules/express/lib/response.js:719:10)
www-2     at ServerResponse.send (/somePath/node_modules/express/lib/response.js:164:12)
www-2     at done (/somePath/node_modules/express/lib/response.js:956:10)
www-2     at Object.exports.renderFile (/somePath/node_modules/jade/lib/index.js:374:12)
www-2     at View.exports.__express [as engine] (/somePath/node_modules/jade/lib/index.js:417:11)
www-2     at View.render (/somePath/node_modules/express/lib/view.js:126:8)
www-2     at tryRender (/somePath/node_modules/express/lib/application.js:639:10)
www-2     at EventEmitter.render (/somePath/node_modules/express/lib/application.js:591:3)
www-2     at ServerResponse.render (/somePath/node_modules/express/lib/response.js:960:7)

Answer 1

问题是我 return 通过 jade 模板处理异常，同时我试图 return json 响应。以下编辑解决了我的问题：

之前：

app.use(function(err, req, res, next) {
  res.status(err.status || 500);
  res.render('error', {
    message: err.message,
    error: {}
  });
});

之后：

app.use(function(err, req, res, next) {
    if(req.body){
        throw err;
    } else {
        res.status(err.status || 500);
        res.render('error', {
            message: err.message,
            error: {}
        });
    }
});

Answer 2

如果您是运行条快递路线，

router.get('/favicon.ico', (req, res) => {
  res.destroy();
});

发送后无法设置headers。节点快递

Can't set headers after they are sent. Nodejs Express

post

header

web-crawler

node.js

express