有没有办法改变这种行为？即让 Rails 懒惰地从池中获取连接，而不是在请求进来时。
我们将 Postgres 用作辅助数据源，因此如果该辅助数据源关闭，应用程序不应受到影响，我们希望从中拯救。
现在，当 postgres 出现故障时，所有请求都会受到影响。
任何输入将不胜感激。
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/connection_adapters/postgresql_adapter.rb:1213:in `initialize'
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/connection_adapters/postgresql_adapter.rb:1213:in `new'
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/connection_adapters/postgresql_adapter.rb:1213:in `connect'
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/connection_adapters/postgresql_adapter.rb:329:in `initialize'
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/connection_adapters/postgresql_adapter.rb:28:in `new'
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/connection_adapters/postgresql_adapter.rb:28:in `postgresql_connection'
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:309:in `new_connection'
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:319:in `checkout_new_connection'
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:241:in `block (2 levels) in checkout'
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:236:in `loop'
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:236:in `block in checkout'
vendor/ruby-1.9.3/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize'
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:233:in `checkout'
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:96:in `block in connection'
vendor/ruby-1.9.3/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize'
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:95:in `connection'
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:404:in `retrieve_connection'
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_specification.rb:170:in `retrieve_connection'
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_specification.rb:144:in `connection'
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/query_cache.rb:67:in `rescue in call'
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/query_cache.rb:61:in `call'
vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:473:in `call'
vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.8/lib/action_dispatch/middleware/callbacks.rb:28:in `block in call'
vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:405:in `_run__1061097989250305020__call__4547997776545495741__callbacks'
vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:405:in `__run_callback'
vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:385:in `_run_call_callbacks'
vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:81:in `run_callbacks'
vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.8/lib/action_dispatch/middleware/callbacks.rb:27:in `call'
vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.8/lib/action_dispatch/middleware/remote_ip.rb:31:in `call'
vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.8/lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call'
vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.8/lib/action_dispatch/middleware/show_exceptions.rb:56:in `call'
vendor/bundle/ruby/1.9.1/gems/railties-3.2.8/lib/rails/rack/logger.rb:26:in `call_app'
vendor/bundle/ruby/1.9.1/gems/railties-3.2.8/lib/rails/rack/logger.rb:16:in `call'
vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.8/lib/action_dispatch/middleware/request_id.rb:22:in `call'
vendor/bundle/ruby/1.9.1/gems/rack-1.4.1/lib/rack/methodoverride.rb:21:in `call'
vendor/bundle/ruby/1.9.1/gems/rack-1.4.1/lib/rack/runtime.rb:17:in `call'
vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.8/lib/action_dispatch/middleware/static.rb:62:in `call'
vendor/bundle/ruby/1.9.1/gems/railties-3.2.8/lib/rails/engine.rb:479:in `call'
vendor/bundle/ruby/1.9.1/gems/railties-3.2.8/lib/rails/application.rb:223:in `call'
vendor/bundle/ruby/1.9.1/gems/railties-3.2.8/lib/rails/railtie/configurable.rb:30:in `method_missing'
vendor/bundle/ruby/1.9.1/gems/rack-1.4.1/lib/rack/deflater.rb:13:in `call'
vendor/bundle/ruby/1.9.1/gems/unicorn-4.4.0/lib/unicorn/http_server.rb:535:in `process_client'
vendor/bundle/ruby/1.9.1/gems/unicorn-4.4.0/lib/unicorn/http_server.rb:610:in `worker_loop'