Update or Set in Firebase Admin SDK in node js causes infinite callbacks

Question

I am fetching data from a node from Firebase Database and then after doing some calculations I am updating it.

I am using Firebase SDK in node js to perform this task.

Here is the code:

app.get("/setBookedSpots", function (request, response) {
    console.log("booked spots called");

    var verifierEmail = request.query.verifierEmail;
    var toBeBookedSpot = request.query.bookSpot;

    console.log(toBeBookedSpot);

    admin.auth().getUserByEmail(verifierEmail)
        .then(function (userRecord) {
            console.log("Successfully fetched user data:", userRecord.toJSON());

            var verifierId = userRecord.uid;

            var refToUserInformation = db.ref("user/" + verifierId);

            refToUserInformation.child("Society_Name").on("value", function (snapshot) {
                console.log(snapshot.val());
                var SocietyName = snapshot.val();

                refToSocietyBookingStatus = db.ref("Societies/" + SocietyName + "/Society_Parking_Details/Society_Parking_Status");

                refToSocietyBookingStatus.child("Booked_Spots").on("value", function (snapshot) {

                    var Booked_Spots = snapshot.val();

                    console.log(Booked_Spots);
                    console.log("to be booked spot", toBeBookedSpot);

                    Booked_Spots = Booked_Spots.toString() + "," + toBeBookedSpot;

                    console.log("after booked spot", Booked_Spots);
                    refToSocietyBookingStatus.update({
                        "Booked_Spots": Booked_Spots
                    })

                    response.send({ "msg": "success" });
                })
            })
        });
});

I am getting the booked spots and the updating them based on the request parameter.

When I hit it, it goes in infinite callback. What I mean to say is it keeps on appending recursively as there is no loop which makes it to crash.

I tried using a different variable for the database reference so that it might not be calling the parent event again but still the same problem.

Here is the service call url:

http://localhost:8080/[email protected]&bookSpot=A7

Peter Haddad · Accepted Answer · 2018-05-10 12:53:42Z

1

you may use instead of response.send({ "msg": "success" }); to change this one response.send(JSON.stringify({ msg: 'success'}));

edited May 10, 2018 at 12:53

Peter Haddad

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answered May 10, 2018 at 12:45

Arkan Malek_AM

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3 Comments

Naman Khandelwal Over a year ago

I just tried your solution, but still infinite loop.

Arkan Malek_AM Over a year ago

in your client side code use if condition check the msg.equals("success") or not..

Naman Khandelwal Over a year ago

But the problem is not regarding the response, I am getting correct response if I remove refToSocietyBookingStatus.update({ "Booked_Spots": Booked_Spots })

Naman Khandelwal · Accepted Answer · 2018-05-10 13:17:21Z

1

After trying a lot, I came to know that the on("value") event was being executed as I was updating the same node from which I just retrived value and thus went in recursion and kept on calling as it went on updating.

Here is the solution to that: replaced on("value") with once("value")

Making it execute just once.

answered May 10, 2018 at 13:17

Naman Khandelwal

1288 bronze badges

1 Comment

Frank van Puffelen Over a year ago

Using on() in Cloud Functions is a pretty explicit anti-pattern, as it leads to hard to debug behavior. Good to see that you found the solution yourself!

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