检查mysql连接到远程主机

我有模型来存储数据库连接参数（主机，数据库名称，用户名，密码）并填写它的形式。在创建或更新之前，我需要检查连接是否适合输入的参数。我创建validate :check_connection验证：检查mysql连接到远程主机

# don`t change primary connection 
class Remote < ActiveRecord::Base; end 

def check_connection 
    return if errors.any? || (!new_record? && password.empty?) 
    begin 
    Remote.establish_connection(
     adapter: 'mysql2', 
     host: host, 
     username: username, 
     password: password, 
     database: database, 
     connect_timeout: 5, 
     reconnect: false 
    ) 
    # maybe need to make some sql request? did try it 
    rescue Exception => e 
    errors.add :connection, 'Could not connect to database' 
    end 
end

当我试图进入访问主机（localhost），像上面的代码工作良好。但如果主机像192.168.1.1（无法访问）页面冻结后提交表单。我看到每秒连接的尝试，并且它在浏览器（停止加载页面）后不停止（我在网络接口上看到tcpdump的尝试）。并尝试不停止。

那么，我该如何验证连接到数据库？而如果连接不能建立，页面必须不会加载很长时间。

来源

2012-08-30 Yuriy Kolodovskyy

我尝试在轨控制台'Mysql2 :: Client.new（主持人： '192.168.1.1'，数据库： 'test'，用户名：'user'，密码：'pass'，connect_timeout：1，read_timeout：1，write_timeout：1）'并且永久尝试连接。超时不起作用。哪里不对？ –

我确实使用gem 'mysql2'和捆绑安装0.3.11版本。此版本忽略connect_timeout并修正了较新版本的错误。在我尝试0.3.12b4（gem 'mysql2', '~> 0.3.12b4'）之后，一切正常。

来源

2012-08-30 11:04:58

phew，一年后，0.3.12还没有发布还是:( – Kevin

变量connect_timeout是一个全局变量。因此，mysql2可能会忽略它。

上mysql5.6：

mysql[(none)]> set connect_timeout = 123; 
ERROR 1229 (HY000): Variable 'connect_timeout' is a GLOBAL variable and should be set with SET GLOBAL

我设置timeout变量初始化mysql2时，但它没有体现出来。 mysql2自述文件说，你可以设置*超时选项，但我认为自述文件已过时或损坏。

上mysql2 0.3.14（GEM）：

client = Mysql2::Client.new(
    host: 'localhost', 
    database: 'test', 
    username: 'root', 
    password: '', 
    connect_timeout: 3, 
    read_timeout: 3, 
    write_timeout: 3, 
    wait_timeout: 3); 

client.query('show variables like "%timeout%"').map{|r| [r["Variable_name"], r["Value"]] } 

=> [["connect_timeout", "10"], 
["delayed_insert_timeout", "300"], 
["innodb_lock_wait_timeout", "50"], 
["innodb_rollback_on_timeout", "OFF"], 
["interactive_timeout", "28800"], 
["lock_wait_timeout", "31536000"], 
["net_read_timeout", "30"], # Maybe older mysql has read_timeout? 
["net_write_timeout", "60"], # Maybe older mysql has write_timeout? 
["slave_net_timeout", "3600"], 
["wait_timeout", "28800"]]

如果使用ActiveRecord，您可以通过设置database.yml仅wait_timeout变量。

在database.yml中

：

development: 
    adapter: mysql2 
    encoding: utf8 
    charset: utf8 
    database: test 
    pool: 5 
    username: root 
    password: 
    host: localhost 
    connect_timeout: 3 
    read_timeout: 3 
    write_timeout: 3 
    wait_timeout: 3

的ActiveRecord 4.0.1的结果：

> ActiveRecord::Base.connection.execute('show variables like "%timeout%"').to_a 
=> [["connect_timeout", "10"], 
["delayed_insert_timeout", "300"], 
["innodb_flush_log_at_timeout", "1"], 
["innodb_lock_wait_timeout", "50"], 
["innodb_rollback_on_timeout", "OFF"], 
["interactive_timeout", "28800"], 
["lock_wait_timeout", "31536000"], 
["net_read_timeout", "30"], 
["net_write_timeout", "60"], 
["rpl_stop_slave_timeout", "31536000"], 
["slave_net_timeout", "3600"], 
["wait_timeout", "3"]]

ActiveRecord的设置wait_timeout变量abstract_mysql_adapter.rb。

看到：

abstract_mysql_adapter.rb https://github.com/rails/rails/blob/master/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

mysql2_adapter.rb https://github.com/rails/rails/blob/master/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb

来源

2014-09-13 11:52:38

检查mysql连接到远程主机

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