在Node.js中如何实现mysql事务自动回收连接

var mysql = require('mysql'),
 Connection = require('mysql/lib/Connection.js');
var pool = mysql.createPool({
 host: '127.0.0.1',
 database: 'myDB',
 port: 3306,
 user: 'root',
 password: 'root',
 debug: false,
 connectionLimit: 3
});
var execPool = function() {
 pool.getConnection(function(err, conn) {
 transAutoRelease(conn);
 conn.beginTransaction(function(err) {
 if (err) throw err;
 conn.query("INSERT INTO test(id,name,date,test) values(1,'123',now(),1)",
 function(err, ret) {
 if (err) {
 console.error(err);
 conn.rollback(function() {});
 } else {
 console.log(ret);
 conn.query('UPDATE test set id=12321312 where id=1', function(err, ret) {
 if (err) {
 console.error(err);
 conn.rollback(function() {
 });
 } else {
 conn.commit(function() {
 console.log('success' + JSON.stringify(ret));
 });
 }
 });
 }
 });
 });
 });
}
function after(fn, cb) { return function() {
 fn.apply(this, arguments);
 cb();
 }
}
function transAutoRelease(conn) {
 if (conn.commit == Connection.prototype.commit)
 conn.commit = after(conn.commit, release);
 if (conn.rollback == Connection.prototype.rollback)
 conn.rollback = after(conn.rollback, release);
 function release() {
 if (conn) {
 conn.release();
 }
 }
}
var intervalStartProcess = function() {
 setInterval(function() {
 execPool();
 }, 1000);
}
for (var i = 5 - 1; i >= 0; i--) {
 intervalStartProcess();
}