问题描述

我有一个非常简单的程序，我在其中创建了一个 Sequelize 实例，然后对 mysql 数据库执行原始查询.情况是当MySql启动并运行没有问题时，我可以毫无问题地执行查询.但是当 MySql 没有运行时，查询不会发出任何错误，直到达到查询超时，然后它会发出 ETIMEOUT 错误.但事实并非如此.如果 mysql 未运行，我希望查询会发出 ENOTFOUND 错误或类似的错误，因此如果 Mysql 已关闭或 Mysql 非常忙并且响应时间非常长，我可以管理错误并执行不同的操作.我应该怎么做才能检查 Mysql 是否已启动并运行而无需等待超时异常.

I have a very simple program in where I create a Sequelize instance and then I perform a raw query on a mysql database. The case is that when MySql is up and running there is no problem, I can perform the query with no problems. But when MySql is not running then the query doesn't emmit any error until the query timeout has reached and then it emmits a ETIMEOUT error. But that's not really what's happening. I expect the query to emit ENOTFOUND error or something like that if mysql is not running so I can manage the error and perform different actions if Mysql has gone down or Mysql is very busy and has a very large response time. What shoul'd I do to check if Mysql is up and running without having to wait the timeout exception.

sequelize = new Sequelize(db_name, db_user, db_pass, opts);

sequelize.query('SELECT * FROM some_table').success(function(result) {
  console.log(result);
}).error(function(err) {
  console.log(err);
});

推荐答案

截至最新版本 Sequelize(即3.3.2)，authenticate 可用于检查连接:

As of latest version of Sequelize (i.e. 3.3.2), authenticate can be used to check the connection:

var sequelize = new Sequelize("db", "user", "pass");

sequelize.authenticate().then(function(errors) { console.log(errors) });

authenticate 只需运行 SELECT 1+1 AS result 查询来检查数据库连接.

authenticate simply runs SELECT 1+1 AS result query to check the db connection.

更新:

最新 API 需要的错误在catch中处理:

Errors by the newest API need to be handled in catch:

sequelize
  .authenticate()
  .then(() => {
    console.log('Connection has been established successfully.');
  })
  .catch(err => {
    console.error('Unable to connect to the database:', err);
  });

更新 2:

我没有对此进行测试，但唯一合乎逻辑的是，使用 async/await 可以达到相同的效果:

I haven't tested this, but its only logical that the same thing can be reached with async/await:

try {
  await sequelize.authenticate()
} catch (err) {
  console.error('Unable to connect to the database:', err)
}

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