Webwork-threads Nodejs access function/variable outside scope

Question

I am facing issue in accessing javascript function or any variable in worker thread. I am using WebWorker-thread nodejs library to perform multithreading.

var fs = require('fs');
var path = require('path');
var threadPool=Worker.createPool(5).all.eval(writeKeywordsToFile);

function getKeywords() {

    var keywords = ["Restaurant", "Food", "Cusine"];
    for (var i = 0; i < keywords.length; i++) {
        threadPool.any.eval('writeKeywordsToFile(' + JSON.stringify(keywords[i]) + ',' + i + ',' + JSON.stringify(path.join(__dirname, '../', 'tmp/')) + ')', function (err, val) {
            console.log(' [' + this.id + '] ---- >'  + err);                

        });
        //writeKeywordsToFile(keywords[i], i , path.join(__dirname, '../', 'tmp/'));
    }
}

function writeKeywordsToFile(keywords, i, dirPath) {


    if (keywords != undefined) {
        var fileName = "Document_" + i + ".txt";
        console.log(fileName);
        var stream = fs.createWriteStream(dirPath + fileName, fs);

        stream.once('open', function (fd) {
            console.log('stream open');

            stream.write(keywords + "\r\n");
            stream.end();
        });
    }
    return keywords;
}

getKeywords();

Unable to access fs to createstream and write to file. How can I access any javascript function or variable inside writeKeywordsToFile(), any workaround ?

Windgazer · Accepted Answer · 2015-07-14 08:26:53Z

1

Workers can only communicate with your original scope by sending/receiving messages to/from that scope. For all intents and purposes you should treat a thread as living in it's own separate scope. I will admit that my experience is based solely on working with actual web-workers, so I'm not sure in how far this applies to your node-based solution (although it should apply since multi-threading on shared scopes would invite hell and damnation on your code)

Thus, anything you've got on your global scope within the main thread simply does not exist in it's workers' scope...

You'll have to require('fs') in the worker if you want to do anything with it.

answered Jul 14, 2015 at 8:26

Windgazer

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2 Comments

xtremist Over a year ago

but the problem is that I can't even access "require" keyword in the worker thread. Strange is that I can access console.write but not "require" :(

Windgazer Over a year ago

I dug around a little and found that the lib you're using, although attempting to come close to actual web-workers does miss out on a few features of said workers. There's indeed no 'require' available. Those workers are really only intended for doing computational heavy-lifting on a limited data-set and reporting the outcome back to the main thread.

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