Exit the process when multiple async operations completed

Question

I want to exit node process when all data will be processed (fetch data, http request with axios and update data). When I run my script by typing node script.js it never ends. Where should I use process.exit() in my script to be sure all data has been processed? Script below:

Keyword.find({
        images: {
            $eq: []
        }
    })
    .limit(8)
    .exec((err, keywords) => {
        keywords.forEach((keyword) => {
            console.log(keyword.body);
            axios.get('https://www.example.com/?q=' + encodeURIComponent(keyword.body))
                .then(function (response) {
                    const dom = new JSDOM(response.data);
                    let items = dom.window.document.querySelectorAll('div.item');
                    let images = [];
                    items.forEach(((item) => {
                        let url = item.querySelector('a.thumb').href;
                        let source = item.querySelector('a.tit').href;
                        let description = item.querySelector('div.des').innerHTML;
                        images.push({
                            url,
                            source,
                            description
                        });
                    }));

                    Keyword.findByIdAndUpdate({
                        _id: keyword._id
                    }, {
                        $set: {
                            images
                        }
                    }, (err2, result2) => {
                        if (err2) console.log(err2);
                        console.log(result2);
                    });
                })
                .catch(function (error) {
                    console.log(error);
                });
        });
    });

Possible duplicate of [How to exit in Node.js](https://stackoverflow.com/questions/5266152/how-to-exit-in-node-js) — Claus Jørgensen, Aug 22 '18 at 18:23
If you're not looking for `process.exit(..)` Nothing in your code indicates you're blocking the runloop, which is why your code don't exit when it's done (assuming you run in a terminal environment, and not Electron et.al.). You should post mode code and rephrase your question — Claus Jørgensen, Aug 22 '18 at 18:42

score 3 · Accepted Answer · answered Aug 22 '18 at 18:55

Seems like your database connection is keeping your app from automatically exit. So you should either close the database connection or call process.exit() when you have done your work.

You are doing multiple async operations simultaneously

keywords.forEach((keyword) => {
    axios.get(...

To be notified when all the operations completed you can create a Promise array and listens to them by Promise.all() method

const operations = keywords.map((keyword) => axios.get('').then((response) => {
    ...
    return new Promise((resolve, reject) => {
        Keyword.findByIdAndUpdate(query, update, (err2, result2) => {
            if (err2) {
                console.log(err2);
                reject(err2);
            }
            console.log(result2);
            resolve();
        });
    });
}));

Promise.all(operations).then(()=>{
    console.log('All done.');
    process.exit();
});

This is the answer I was looking for. Thank you for help! – Joey Nie Aug 22 '18 at 18:59 — Joey Nie, Aug 22 '18 at 18:59

score 1 · Answer 2 · answered Aug 22 '18 at 18:26

1

From the docs:

The process.exit() method instructs Node.js to terminate the process synchronously with an exit status of code. If code is omitted, exit uses either the 'success' code 0 or the value of process.exitCode if it has been set. Node.js will not terminate until all the 'exit' event listeners are called.

To exit with a 'failure' code:

process.exit(1);

answered Aug 22 '18 at 18:26

Chaim Ochs

119
9

I know about process.exit(), but question is where to put this line, to be able to exit AFTER all data will be processed correctly? – Joey Nie Aug 22 '18 at 18:33
FYI, rather than duplicate answers, it's better to vote to close a question. – Claus Jørgensen Aug 22 '18 at 18:41

Exit the process when multiple async operations completed

2 Answers2