Multiple child_process exec on node js

Question

I am trying to get data using curl on nodejs. I need to run more than one child_process for each query in order to retrieve the data without delays.

router.post('/curl/', function* () { var urls = this.request.body.url; var exec = require('child_process').exec; var promise = new Promise((resolve, reject) => { var count = urls.length; var res = _.map(urls, (stream) => { // stream = {url:'http://url1.com'}; var command = 'curl '+stream.url+'; exec(command, (error, stdout, stderr) => { if (error !== null) { console.log('exec error: ' + error); } return stdout; }); }); resolve(res); }); this.body = yield promise; });

This resolve '[null, null]'; I was tried to use Promise.map, but it was failed too.

If I make a single request (without _.map()) - it returns HTML of the requested page, as I expect. How to run more than one child_process for my requests?

Sangharsh · Accepted Answer · 2017-02-10 06:48:15Z

Here is a variant without generator (function*). It is unclear what are you trying to do with generator.

var exec = require('child_process').exec; router.post('/curl/', function() { function processUrl(url) { return new Promise((resolve, reject) => { var command = 'curl ' + stream.url; exec(command, (error, stdout, stderr) => { if (error) return reject(error); return resolve(stdout); }); }); } var urls = this.request.body.url; var allPromises = urls.map(url => { return processUrl(url); }); Promise.all(allPromises) .then(htmls => { console.log('HTML of pages:', htmls.length); }); });

I use generator to wrap all the code into Promise, and run it as 'this.body = yield promise'.

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