function copydb(_sourceUrl, _destinationUrl, _db, _sourceAdminUsername, _sourceAdminPassword) {
return new Promise((resolve, reject) => {
    mongoClient.connect(_destinationUrl + "/" + _db)
        .then(destinationDB => {
            destinationDB.admin().command({
                copydb: 1,
                fromhost: _sourceUrl,
                fromdb: _db,
                username: _sourceAdminUsername,
                todb: _db,
                nonce: "some-nonce",
                key: {
                    username: _sourceAdminUsername,
                    password: _sourceAdminPassword
                }
            }, function (err, res) {
                if (err) {
                    reject(err)
                } else {
                    resolve(res)
                }
                destinationDB.close();
            })
        }).catch(err => reject(err))
})