我正在使用ActiveRecord版本3.2.14（并尝试了3.2.15 rc）和TinyTDS + activerecord sql适配器连接到我的SQL Server数据库。
在抛出此异常的地方，我遇到了非常奇怪的行为：
/usr/local/rvm/gems/ruby-1.9.3-p448/gems/activerecord-3.2.14/lib/active_record
/connection_adapters/abstract/connection_pool.rb:410:in `retrieve_connection':
ActiveRecord::ConnectionNotEstablished (ActiveRecord::ConnectionNotEstablished)
但根据痕迹：
from /usr/local/rvm/gems/ruby-1.9.3-p448/gems/activerecord-3.2.14/lib/active_record/connection_adapters/abstract/connection_specification.rb:171:in `retrieve_connection'
from /usr/local/rvm/gems/ruby-1.9.3-p448/gems/activerecord-3.2.14/lib/active_record/connection_adapters/abstract/connection_specification.rb:145:in `connection'
from /usr/local/rvm/gems/ruby-1.9.3-p448/gems/activerecord-3.2.14/lib/active_record/model_schema.rb:229:in `columns'
from /usr/local/rvm/gems/ruby-1.9.3-p448/gems/activerecord-3.2.14/lib/active_record/model_schema.rb:249:in `column_names'
from /usr/local/rvm/gems/ruby-1.9.3-p448/gems/activerecord-3.2.14/lib/active_record/model_schema.rb:262:in `column_methods_hash'
from /usr/local/rvm/gems/ruby-1.9.3-p448/gems/activerecord-3.2.14/lib/active_record/dynamic_matchers.rb:74:in `all_attributes_exists?'
from /usr/local/rvm/gems/ruby-1.9.3-p448/gems/activerecord-3.2.14/lib/active_record/dynamic_matchers.rb:27:in `method_missing'
from /usr/local/debugging-exchange-test/app/controllers/new_orders_controller.rb:15:in `block in start'
from /usr/local/rvm/gems/ruby-1.9.3-p448/gems/activerecord-3.2.14/lib/active_record/relation/delegation.rb:6:in `each'
from /usr/local/rvm/gems/ruby-1.9.3-p448/gems/activerecord-3.2.14/lib/active_record/relation/delegation.rb:6:in `each'
from /usr/local/debugging-exchange-test/app/controllers/new_orders_controller.rb:13:in `start'
from /usr/local/debugging-exchange-test/lib/exchange.rb:57:in `testing'
from /usr/local/debugging-exchange-test/lib/exchange.rb:39:in `initialize'
from /usr/local/debugging-exchange-test/lib/exchange.rb:104:in `new'
from /usr/local/debugging-exchange-test/lib/exchange.rb:104:in `<top (required)>'
from /usr/local/rvm/gems/ruby-1.9.3-p448/gems/daemons-1.1.9/lib/daemons/application.rb:203:in `load'
from /usr/local/rvm/gems/ruby-1.9.3-p448/gems/daemons-1.1.9/lib/daemons/application.rb:203:in `start_load'
from /usr/local/rvm/gems/ruby-1.9.3-p448/gems/daemons-1.1.9/lib/daemons/application.rb:298:in `start'
from /usr/local/rvm/gems/ruby-1.9.3-p448/gems/daemons-1.1.9/lib/daemons/controller.rb:70:in `run'
from /usr/local/rvm/gems/ruby-1.9.3-p448/gems/daemons-1.1.9/lib/daemons.rb:147:in `block in run'
from /usr/local/rvm/gems/ruby-1.9.3-p448/gems/daemons-1.1.9/lib/daemons/cmdline.rb:109:in `call'
from /usr/local/rvm/gems/ruby-1.9.3-p448/gems/daemons-1.1.9/lib/daemons/cmdline.rb:109:in `catch_exceptions'
from /usr/local/rvm/gems/ruby-1.9.3-p448/gems/daemons-1.1.9/lib/daemons.rb:146:in `run'
from ./data_exchange:15:in `<main>'
它发生在each方法上：
def start
web_queue = Nti::Order.where("orderid IS NOT NULL AND updated_by_exchange_at IS NULL AND orderstatus <> 9")
logger.info "web_queue size: #{web_queue.length}"
web_queue.each do |nti_order| #<---- this line
# logger.info nti_order.orderid
web_order = Web::Order.find_by_id(nti_order.orderid)
raise "Couldn't find web order with ID #{nti_order.orderid}" if web_order.nil?
web_order.status = 99
web_order.save!
logger.info "Web order with ID #{web_order.id} updated to status = 99"
end
end
在发生这种情况之前，我得到了相同的确切错误，但由于.size方法，对于这一行：
logger.info "web_queue size: #{web_queue.size}"
当我将其更改为.length时，它可以工作。这到底是怎么回事？这些方法与ActiveRecord无关。我的数组方法正在引发活动记录异常。
顺便说一句，这是一个Ruby应用程序（不是Rails），它使用ActiveRecord在两个数据库之间交换数据。
只是为了表明数据库连接有效，当我更改方法来执行此操作时：
def start
a = Nti::Order.where("orderid IS NOT NULL AND updated_by_exchange_at IS NULL AND orderstatus <> 9")
logger.info a.first.inspect
logger.info "done"
end
它有效。这也适用于：
def start
a = Nti::Order.where("orderid IS NOT NULL AND updated_by_exchange_at IS NULL AND orderstatus <> 9")
# logger.info a.size
puts a.map{ |order| order.orderid }
logger.info "done"
end
有人知道发生了什么吗？
尝试增加 database.yml 中的池大小。将默认pool: 5更改为较大的内容。