How to trigger firebase http function in node.js?

Question

I am trying to trigger an another function in Firebase Cloud function with javascript. But i always getting an error of Can't set headers after they are sent. Please take a look at my code below: ................. ................. ............ ................ ................. ............... ....................... .................. ..............

exports.productIndexShuffleOne = functions.https.onRequest(async (req, res) => {
    const interval = req.query.interval;
    console.log("interval: "+interval);

    const productRef = admin.firestore().collection("Products");
    const adminRef = admin.firestore().collection("Admin").doc("totalProd").get();
    const dateRef = admin.firestore().collection("Admin").doc("totalProd").collection("indexShuffle").doc("productShuffle").get();

    return dateRef.then(documentSnapshot => {
        const setDate = documentSnapshot.get('date').seconds;

        var nextDay = setDate;
        console.log("Date: "+nextDay);

        const x = setInterval(function() {
            clearInterval(x);
            return Promise.all([adminRef]).then(result => {
                const totalNum = result[0].data().totalNumber;

                console.log("totalNum: "+totalNum);

                var numberList = [];
                var index = 1;
                while(index <= totalNum){
                    numberList.push(index);
                    index++;
                }

                var cidx, ridx, tmp;
                cidx = numberList.length;
                while (cidx !== 0) {
                    ridx = Math.floor(Math.random() * cidx);
                    cidx--;
                    tmp = numberList[cidx];
                    numberList[cidx] = numberList[ridx];
                    numberList[ridx] = tmp;
                }
                console.log(numberList);

                var counter = 0;
                return productRef.get().then(snapshot => {
                    snapshot.forEach(doc => {
                    const prodID = doc.get('productID');
                    const index = doc.get('index');

                    var newIndex = numberList[counter];
                    counter++;
                    console.log("oldIndex: "+index);
                    console.log("newIndex: "+newIndex);

                    productRef.doc(prodID).update({
                        index: newIndex
                        }, {merge: true});
                    });

                    return res.redirect('https://us-central1-myfunction-123456.cloudfunctions.net/productIndexShuffleTwo?interval='+interval);
                })
                .catch(err => {
                    console.log('Error getting documents', err);
                });
            });
        }, interval);
        return res.status(203).send(interval);
    }).catch(function(err) {
        console.error(err);
    });
});

Answer 1

This is because you've sent multiple responses while the rule is that you only allowed sending one response. Please try to look at your code and optimize it in such a way that it contains only one response.

I can see you have multiple responses as below:

1 -> return res.redirect('https://us-central1-myfunction-123456.cloudfunctions.net/productIndexShuffleTwo?interval='+interval);

2 -> return res.status(203).send(interval);

Answer 2

I believe that you can have res.redirect and then res.status.send called one after another. When you writing endpoints there rule of a thumb: always send response and only do that once. Refactor your code so there no way you can make those two calls, but only one of them.