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我想将数据扇出到 4 个不同的节点。由于firebase事务过程可能会失败，确保所有4个数据都被保存的正确方法是什么？

假设我有 4 个保存数据的函数，每个函数都会调用一个事务。

编辑：

function saveToFirstNode(data, response) {
    /*
     * @param
     * [response] is a callback function 
     * that indicates whether the save was successful
     */ 
    firebase.database().ref('cars/' + data.carId)
        .transaction(function(currentData) {
        currentData.distance += data.distance;
        return currentData;
    }, function(error, commited, snapshot) {
        if (error) {
            response(false);
        } else if (commited) {
            response(true)
        }
    }, false);
}
function saveToSecondNode(data, response) {...}
function saveToThirdNode(data, response) {...}
function saveToFourthNode(data, response) {...}

1.使用第一种方法

这种方法使用嵌套的回调函数，并在每次保存成功时调用 progress()。
缺点是，如果其中一个保存过程失败，它将重新保存从第一个到第四个的所有数据。

var queue = new Queue(ref, options, function(data, progress, resolve, reject) {
    saveToFirstNode(data, function(success) {
        if (success) {
            progress(25);
            saveToSecondNode(data, function(success) {
                if (success) {
                    progress(50);
                    saveToThirdNode(data, function(success) {
                        if (success) {
                            progress(75);
                            saveToFourthNode(data, function(success) {
                                if(success) {
                                    resolve(data);
                                } else {
                                    reject();
                                }
                            });
                        } else {
                            reject();
                        }
                    });
                } else {
                    reject();
                }
            });
        } else {
            reject();
        }
    });
});

2.使用第二种方法

这种方法保证所有数据都将被保存。当保存过程失败时，它将从失败的规范重试，而不是从第一个到第四个。但是您认为仅进行4次保存就大材小用了吗？这是正确的方法吗？

在队列/规格中定义规格：

{
    "save_to_first_node": {
        "in_progress_state": "save_to_first_node_in_progress",
        "finished_state": "save_to_first_node_finished"
    }, 
    "save_to_second_node": {
        "start_state": "save_to_first_node_finished",
        "in_progress_state": "save_to_second_node_in_progress",
        "finished_state": "save_to_second_node_finished"
    }, 
    "save_to_third_node": {
        "start_state": "save_to_second_node_finished",
        "in_progress_state": "save_to_third_node_in_progress",
        "finished_state": "save_to_third_node_finished"
    }, 
    "save_to_fourth_node": {
        "start_state": "save_to_third_node_finished",
        "in_progress_state": "save_to_fourth_node_in_progress"
    }
}

队列代码：

var saveToFirstNodeOptions = {'specId': 'save_to_first_node'};
var saveToFirstNodeQueue = new Queue(ref, saveToFirstNodeOptions, function(data, progress, resolve, reject) {
    saveToFirstNode(data, function(success) {
        if (success) resolve(data);
        else reject();
    });
});

var saveToSecondNodeOptions = {'specId': 'save_to_second_node'};
var saveToSecondNodeQueue = new Queue(ref, saveToSecondNodeOptions, function(data, progress, resolve, reject) {
    saveToSecondNode(data, function(success) {
        if (success) resolve(data);
        else reject();
    });
});

var saveToThirdNodeOptions = {'specId': 'save_to_third_node'};
var saveToThirdNodeQueue = new Queue(ref, saveToThirdNodeOptions, function(data, progress, resolve, reject) {
    saveToThirdNode(data, function(success) {
        if (success) resolve(data);
        else reject();
    });
});

var saveToFourthNodeOptions = {'specId': 'save_to_fourth_node'};
var saveToFourthNodeQueue = new Queue(ref, saveToFourthNodeOptions, function(data, progress, resolve, reject) {
    saveToFourthNode(data, function(success) {
        if (success) resolve(data);
        else reject();
    });
});

哪种方法是正确的？这个问题不是偏好，因为这两者是完全不同的方法，对性能和有效性都产生巨大影响。

4

0 回答 0