Error: data update to database failed due to technical issues

Question

Error: data update to database failed due to technical issues

Struggling with updating data to MongoDB using Express. Despite receiving a status 200 response from my API, I can't seem to update the values in Mongoose when using Mongoskin.

var mongo = require('mongoskin');
var db = mongo.db(config.connectionString, {
    native_parser: true
});
var ObjectId = require('mongodb').ObjectID;
db.bind('users');
db.bind('dashboard')

function update(_id, userParam) {
    var deferred = Q.defer();

    for (var i = 0; i < Object.keys(userParam).length; i++) {
        var set = {

            file: userParam[i].file,
            result: userParam[i].result,
            user_id: userParam[i].user_id

        };
        db.dashboard.update({
                _id: mongo.helper.toObjectID(_id)
            }, {
                $set: set
            },
            function(err, doc) {
                if (err) deferred.reject(err);
                deferred.resolve();
            });
    };
    return deferred.promise;
}

This is how my API looks:

{
    "0": {
        "_id": "57396e49a6c36801024021a1",
        "file": "app_static/audio/SampleAudio_0.4mb.mp3",
        "result": "FM",
        "user_id": "57396ded0aef5ee405320dbe"
    },
    "1": {
        "_id": "57396e5ca6c36801024021a2",
        "file": "app_static/audio/SampleAudio_0.7mb.mp3",
        "user_id": "57396ded0aef5ee405320dbe"
    }
}

I'm utilizing a for loop to ensure the entire API is processed and pushed to MongoDB.

If you have any suggestions for an alternative way to push an entire JSON to MongoDB, please share them.

Your assistance is greatly appreciated!

Thank you in advance.

javascript mongodb express

Answer 1

Answer №1

db.dashboard.update is a function that operates asynchronously (also known as non-blocking) and requires a callback as an argument.

You are invoking db.dashboard.update multiple times within a for loop, however, in the callback, you are either rejecting or resolving the same promise.

This implies that the then method of the returned promise will only be executed when the callback of the initial call to db.dashboard.update is triggered.

Subsequent update operations will not trigger your then function at all.

POTENTIAL SOLUTIONS:

1

Encapsulate your asynchronous code within an IIFE and invoke your deferred.resolve during the final iteration of the loop.

function update(_id, userParam) {

    var deferred = Q.defer();

    var length = Object.keys(userParam).length;

    for (var i = 0; i < length; i++) {
        var set = {

            file: userParam[i].file,
            result: userParam[i].result,
            user_id: userParam[i].user_id

        };

        (function(set, i) { // <------------------------- enclosing everything in an IIFE

            db.dashboard.update({
                    _id: mongo.helper.toObjectID(_id)
                }, {
                    $set: set
                },
                function(err, doc) {
                    if (err) {
                        deferred.reject(err);
                    } else if (length - 1 === i) { // <-- checking if this is the last iteration
                        deferred.resolve();
                    }
                });

        })(set, i); // <--------------------------------- sharing set and i with the IIFE scope
    };

    return deferred.promise;
}

2

Consider using async.map. This approach provides a more elegant solution.

function update(_id, userParam) {

    var deferred = Q.defer();

    /**
     * Array to store all sets
     */
    var arrayOfSets = [];

    /**
     * Convert key-value pairs in userParam to array elements and push into arrayOfSets
     */
    for (var i in userParam) {
        arrayOfSets.push({

            file: userParam[i].file,
            result: userParam[i].result,
            user_id: userParam[i].user_id

        });
    }

    /**
     * Execute async.map
     */
    async.map(arrayOfSets, function(item, callback) {

        db.dashboard.update({
                _id: mongo.helper.toObjectID(_id)
            }, {
                $set: item
            },
            function(err, doc) {
                if (err) {
                    callback(err, null);
                } else {
                    callback(null, doc);
                }
            });

    }, function(err, result) {

        if (err) {
            deferred.reject(err);
        } else {
            deferred.resolve(result);
        }

    });

    return deferred.promise;

}

Remember, always enclose else statements within an if...else block!

function(err, doc) {
    if (err) {
        deferred.reject(err);
    } else { // always enclose in else!
        deferred.resolve();
    }
}

Answer 2

db.dashboard.update is a function that operates asynchronously (also known as non-blocking) and requires a callback as an argument.

You are invoking db.dashboard.update multiple times within a for loop, however, in the callback, you are either rejecting or resolving the same promise.

This implies that the then method of the returned promise will only be executed when the callback of the initial call to db.dashboard.update is triggered.

Subsequent update operations will not trigger your then function at all.

POTENTIAL SOLUTIONS:

1

Encapsulate your asynchronous code within an IIFE and invoke your deferred.resolve during the final iteration of the loop.

function update(_id, userParam) {

    var deferred = Q.defer();

    var length = Object.keys(userParam).length;

    for (var i = 0; i < length; i++) {
        var set = {

            file: userParam[i].file,
            result: userParam[i].result,
            user_id: userParam[i].user_id

        };

        (function(set, i) { // <------------------------- enclosing everything in an IIFE

            db.dashboard.update({
                    _id: mongo.helper.toObjectID(_id)
                }, {
                    $set: set
                },
                function(err, doc) {
                    if (err) {
                        deferred.reject(err);
                    } else if (length - 1 === i) { // <-- checking if this is the last iteration
                        deferred.resolve();
                    }
                });

        })(set, i); // <--------------------------------- sharing set and i with the IIFE scope
    };

    return deferred.promise;
}

2

Consider using async.map. This approach provides a more elegant solution.

function update(_id, userParam) {

    var deferred = Q.defer();

    /**
     * Array to store all sets
     */
    var arrayOfSets = [];

    /**
     * Convert key-value pairs in userParam to array elements and push into arrayOfSets
     */
    for (var i in userParam) {
        arrayOfSets.push({

            file: userParam[i].file,
            result: userParam[i].result,
            user_id: userParam[i].user_id

        });
    }

    /**
     * Execute async.map
     */
    async.map(arrayOfSets, function(item, callback) {

        db.dashboard.update({
                _id: mongo.helper.toObjectID(_id)
            }, {
                $set: item
            },
            function(err, doc) {
                if (err) {
                    callback(err, null);
                } else {
                    callback(null, doc);
                }
            });

    }, function(err, result) {

        if (err) {
            deferred.reject(err);
        } else {
            deferred.resolve(result);
        }

    });

    return deferred.promise;

}

Remember, always enclose else statements within an if...else block!

function(err, doc) {
    if (err) {
        deferred.reject(err);
    } else { // always enclose in else!
        deferred.resolve();
    }
}

Error: data update to database failed due to technical issues

Answer №1

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