Question

自从过去2个月以来，我一直在研究nodejs，这是我在处理异步模块时遇到的问题。有时出现一些错误异步错误从异步任务中间调用错误。考虑此代码：

var mysql = require('mysql');
var async = require('async');

var connection = mysql.createConnection({
  host: 'localhost',
  user: 'root',
  database: 'test',
  password: '12345'
});

var chairArr = ['Red', 'Green', 'Yellow', 'Voilet', 'Brown'];
var inventoryName = "Chairs";
addInventory(inventoryName, chairArr, function(err, result) {
  if(err) {
    console.log("Err : "+err);
  }
  console.log("Successfully added an inventory");
});


function addInventory(inventoryName, chairArr, callback) {
  var sqlQuery = "INSERT INTO tb_inventory(name, added_on) VALUES( ?, NOW())";
  connection.query(sqlQuery, [inventoryName], function(err, result) {
    if(err) {
      return callback(err, null);
    }
    var inventoryId = result.insertId;
    var tasks = [];
    for(var i = 0; i < chairArr.length; i++) {
      tasks.push(addChair.bind(null, inventoryId, chairArr[i]));
    }
    async.parallel(tasks, function(taskErr, taskRes) {
      if(taskErr) {
        return callback(taskErr, null);
      }
      callback(null, result);
    });
  });
}

function addChair(inventoryId, chairColor, callback) {
  var sqlQuery = "INSERT INTO tb_chairs(inventory_id, color) VALUES(?, ?)";
  connection.query(sqlQuery, [inventoryId, chairColor], function(err, result) {
    if(err) {
      return callback(err, null);
    }
    callback(null, result);
  });
}

这个简单的程序只需插入两个表tb_inventory和tb_chairs。我的问题是：有时由于来自前端的参数或我的错误查询不执行而异步并行调用该错误回调。有没有办法回滚（即删除表中所有插入的条目。）任何人都可以告诉我如何在错误回调中实现它（即跟踪所有插入的ID并删除那些？）。我们可以全局使用mysql transactions吗？

Answer 1

每当使用一系列函数时，我们都可以从池中获取本地连接，并在异步调用期间调用的函数中传递该本地连接。可以在异步调用的回调中处理提交或回滚。

var mysql = require('mysql');
var async = require('async');

var dbPool = mysql.createPool({
  host: 'localhost',
  user: 'root',
  database: 'test',
  password: '12345',
  connectionLimit: 10
});

//var chairArr = ['Red', 'Green!++++++++++++++++!!!!!!!!!!!!!!!!!!!!!!!!!!!!', 'Yellow', 'Voilet', 'Brown']; //Case where query fails due to VARCHAR(20) limit
var chairArr   = ['Red', 'Green', 'Yellow', 'Voilet', 'Brown'];
var inventoryName = "SOME ITEM ";
dbPool.getConnection(function(conErr, localConnection) {
    localConnection.beginTransaction(function(transactionErr) {
      if(transactionErr)  {
          console.log("There was some error in begining transaction");
          return;
      }
      addInventory(localConnection, inventoryName, chairArr, function(err, result) {
        if(err) {
          console.log("Err : "+err);
          return;
        }
        else {
          console.log("Successfully added an inventory");
        }
      });
    });
});


function addInventory(localConnection, inventoryName, chairArr, callback) {
  var sqlQuery = "INSERT INTO tb_inventory(name, added_on) VALUES( ?, NOW())";
  localConnection.query(sqlQuery, [inventoryName], function(err, result) {
    if(err) {
      return callback(err, null);
    }
    var inventoryId = result.insertId;
    var tasks = [];
    for(var i = 0; i < chairArr.length; i++) {
      tasks.push(addChair.bind(null, localConnection, inventoryId, chairArr[i]));
    }
    async.parallel(tasks, function(err, asyncRes) {
      if(err) {
        rollback(localConnection, function(rollErr, rollRes) {
          return callback(err, null);
        });
      }
      else {
        localConnection.commit(function(commitErr, commitRes) {
          console.log("transaction succeded");
          return callback(null, "Success");
        });
      }
    });
  });
}

function addChair(localConnection, inventoryId, chairColor, callback) {
  var sqlQuery = "INSERT INTO tb_chairs(inventory_id, color) VALUES(?, ?)";
  localConnection.query(sqlQuery, [inventoryId, chairColor], function(err, result) {
    if(err) {
      return callback(err, null);
    }
    callback(null, result);
  });
}

function rollback(localConnection, callback) {
  localConnection.rollback(function(err, result) {
    if(err) {
      console.log("ROLLBACK Failed");
      return callback(err, null);
    }
    console.log("ROLLBACK successful!");
    callback(null, result);
  });
}

我希望它有所帮助。

如何在具有异步模块的nodejs中实现回滚？

1 个答案: