检查mysql与远程主机的连接

我有一个模型来存储数据库连接参数主机，数据库名称，用户名，密码和填写它的形式。在创建或更新之前，我需要检查输入参数的连接是否良好。我创建验证：检查连接验证程序：

# 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

当我尝试输入accessible host localhost时，上面这样的代码效果很好。但如果主机喜欢192.168.1.1不可访问的页面冻结后提交表单。我每秒钟都会看到连接尝试，在ESC停止在浏览器加载页面后，它并没有停止。我在网络接口上看到tcpdump尝试。尝试并没有停止

那个么，如何验证到数据库的连接呢？若无法建立连接，页面必须不会加载很长时间

我确实使用了gem'mysql2'和bundle安装0.3.11版本。此版本忽略连接超时和更新版本修复的错误。在我尝试了0.3.12b4 gem'mysql2'之后，“~>0.3.12b4”一切正常。

变量connect\u timeout是一个全局变量。因此，mysql2可能会忽略它

在mysql5.6上：

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

我在初始化mysql2时设置了超时变量，但没有反映出来。mysql2的自述文件说可以设置*超时选项，但我认为自述文件已经过时或已损坏

在mysql2 0.3.14gem上：

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，则只能通过database.yml设置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

ActiveRecord 4.0.1的一个结果：

> 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在abstract\u mysql\u adapter.rb中设置wait\u timeout变量

见：

抽象_mysql_adapter.rb

mysql2_adapter.rb

---

我尝试在rails控制台Mysql2:：Client.newhost:'192.168.1.1'，数据库：'test'，用户名：'user'，密码：'pass'，连接超时：1，读取超时：1，写入超时：1，并看到永久连接尝试。超时不起作用。怎么了？一年后，0.3.12还没有发布：