Sequel DB连接PoolTimeout错误

Question

我一直无法确定我编写的Ruby脚本中出现以下Sequel::PoolTimeout错误的原因是什么：

Sequel::PoolTimeout: Sequel::PoolTimeout
             hold at /Users/username/.rvm/gems/jruby-1.7.4@all/gems/sequel-4.2.0/lib/sequel/connection_pool/threaded.rb:100
             hold at /Users/username/.rvm/gems/jruby-1.7.4@all/gems/sequel-4.2.0/lib/sequel/connection_pool/threaded.rb:93
      synchronize at /Users/username/.rvm/gems/jruby-1.7.4@all/gems/sequel-4.2.0/lib/sequel/database/connecting.rb:234
          execute at /Users/username/.rvm/gems/jruby-1.7.4@all/gems/sequel-4.2.0/lib/sequel/adapters/jdbc.rb:258
          execute at /Users/username/.rvm/gems/jruby-1.7.4@all/gems/sequel-4.2.0/lib/sequel/dataset/actions.rb:793
       fetch_rows at /Users/username/.rvm/gems/jruby-1.7.4@all/gems/sequel-4.2.0/lib/sequel/adapters/jdbc.rb:671
             each at /Users/username/.rvm/gems/jruby-1.7.4@all/gems/sequel-4.2.0/lib/sequel/dataset/actions.rb:143
    single_record at /Users/username/.rvm/gems/jruby-1.7.4@all/gems/sequel-4.2.0/lib/sequel/dataset/actions.rb:583
     single_value at /Users/username/.rvm/gems/jruby-1.7.4@all/gems/sequel-4.2.0/lib/sequel/dataset/actions.rb:591
              get at /Users/username/.rvm/gems/jruby-1.7.4@all/gems/sequel-4.2.0/lib/sequel/dataset/actions.rb:250
           empty? at /Users/username/.rvm/gems/jruby-1.7.4@all/gems/sequel-4.2.0/lib/sequel/dataset/actions.rb:153
            scrap at /Users/username/projectname/processers/get_category.rb:46
             each at org/jruby/RubyArray.java:1617
  each_with_index at org/jruby/RubyEnumerable.java:920
            scrap at /Users/username/projectname/processers/get_category.rb:44
            scrap at /Users/username/projectname/processers/get_category.rb:32

我用核磁共振和JRuby都试过了，结果完全一样。

根据Sequel gem here上的说明，我尝试提高pool_timeout限制，如下所示：

DB = Sequel.connect("jdbc:mysql://localhost/project_db?user=USERNAME&password=PASSWD&max_connections=10&pool_timeout=120")

似乎max_connections和pool_timeout可能无法识别，但是我没有看到任何其他方法将这些参数传递到连接中。

这里讨论的实际代码是：if DB[:products].where(url: url.to_s).empty?

我已经看到代码在一小段时间内工作得很好，但毫无疑问，它要么立即失败，要么在几分钟后失败，并且没有任何重现性。我开始怀疑这是MySQL配置问题还是什么导致localhost数据库管理系统有一些长时间的延迟，尽管，同样，我不能手动重现可见的超时，我可以通过手动查询来判断，等等。

关于为什么超时会一直发生，或者更具体地说，如何通过提供正确的Sequel设置(可能我有一个格式错误的arg列表)或针对这种情况修改MySQL的/etc/my.cnf，有什么想法吗？

Answer 1

Sequel jdbc适配器将连接字符串直接传递给JDBC，它不会解析出嵌入的选项。您需要做的是：

DB = Sequel.connect("jdbc:mysql://localhost/project_db?user=USERNAME&password=PASSWD", :max_connections=>10, :pool_timeout=>120)