在 sequelize 中检查 mysql 连接

Check mysql connection in sequelize(在 sequelize 中检查 mysql 连接)

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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