javascript - NodeJS/express : server hanged after start running for a while

Question

我使用express和webpack来提供服务，一开始效果很好。奇怪的是，一段时间后服务(服务器)就会挂起。正如屏幕截图所示，没有收到消息代码。 (server message screenshot)而且这种情况一再发生。

我的app.js

var express = require('express');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');

var index = require('./routes/index');
var users = require('./routes/users');

var app = express();
var mysql = require('mysql');

var generals = require('./routes/generals');

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');

app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use('/generals', generals);
app.use(express.static(path.join(__dirname, 'public')));

app.use('/', index);
app.use('/users', users);

// catch 404 and forward to error handler
app.use(function(req, res, next) {
  var err = new Error('Not Found');
  err.status = 404;
  next(err);
});

// error handler
app.use(function(err, req, res, next) {
  // set locals, only providing error in development
  res.locals.message = err.message;
  res.locals.error = req.app.get('env') === 'development' ? err : {};

  // render the error page
  res.status(err.status || 500);
  res.render('error');
});

module.exports = app;

这是路由文件:generals.js

var express = require('express');
var bodyParser = require('body-parser');

var router = express.Router();
var pool = require('./connections');

router.get('/dropDownValue/', function(req, res, next) {
    pool.getConnection(function(err, connection) {
        connection.query("select * from drop_down_value order by id desc", function(err, rows) {
            if (!err && rows.length > 0) {
                res.json(rows);
            } else {
                res.json([]);
            }
        });
    });
});

连接文件:

var mysql = require('mysql');

var pool = mysql.createPool({
    host: 'xxx',
    user: 'xxx',
    password: 'xxx',
    database: 'xxx'
});

exports.getConnection = function (callback) {
    pool.getConnection(callback);
};

Answer 1

当您使用pool.getConnection()时，一旦完成连接(即查询完成)，您需要再次将连接释放回池中:

pool.getConnection(function(err, connection) {
    connection.query("select * from drop_down_value order by id desc", function(err, rows) {

        connection.release(); // <- this

        if (!err && rows.length > 0) {
            res.json(rows);
        } else {
            res.json([]);
        }
    });
});

否则，一旦执行了 10 次查询，池中就没有更多可用连接，它将开始(无限期地)等待连接被释放，从而挂起请求。