我有生产服务器(Nginx Passenger).当我尝试从另一台计算机ab -n 3 -c 3 myhost.ru/时,我在我的Nginx error.log中收到此错误日志：

[ pid=21160 thr=139775297914624 file=ext/Nginx/HelperAgent.cpp:584 time=2011-08-31 15:25:49.22 ]: Uncaught exception in PassengerServer client thread:
   exception: Cannot read response from backend process: Connection reset by peer (104)
   backtrace:
     in 'void Client::forwardResponse(Passenger::SessionPtr&,Passenger::FileDescriptor&,const Passenger::AnalyticsLogPtr&)' (HelperAgent.cpp:330)
     in 'void Client::handleRequest(Passenger::FileDescriptor&)' (HelperAgent.cpp:510)
     in 'void Client::threadMain()' (HelperAgent.cpp:603)

[ pid=21249 thr=15884760 file=utils.rb:176 time=2011-08-31 15:25:49.022 ]: *** Exception PGError in application (server closed the connection unexpectedly
  This probably means the server terminated abnormally
  before or while processing the request.
) (process 21249,thread #sql_adapter.rb:276:in `exec'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/postgresql_adapter.rb:276:in `block in clear_cache!'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/postgresql_adapter.rb:275:in `each_value'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/postgresql_adapter.rb:275:in `clear_cache!'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/postgresql_adapter.rb:303:in `disconnect!'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:202:in `block in disconnect!'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:201:in `each'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:201:in `disconnect!'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activesupport-3.1.0/lib/active_support/core_ext/module/synchronization.rb:35:in `block in disconnect_with_synchronization!'
  from /home/deployer/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/monitor.rb:201:in `mon_synchronize'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activesupport-3.1.0/lib/active_support/core_ext/module/synchronization.rb:34:in `disconnect_with_synchronization!'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:395:in `block in clear_all_connections!'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:395:in `each_value'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:395:in `clear_all_connections!'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/abstract/connection_specification.rb:123:in `clear_all_connections!'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/utils.rb:398:in `before_handling_requests'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/rack/application_spawner.rb:204:in `start_request_handler'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/rack/application_spawner.rb:170:in `block in handle_spawn_application'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/utils.rb:479:in `safe_fork'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/rack/application_spawner.rb:165:in `handle_spawn_application'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/abstract_server.rb:357:in `server_main_loop'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/abstract_server.rb:206:in `start_synchronously'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/abstract_server.rb:180:in `start'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/rack/application_spawner.rb:128:in `start'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/spawn_manager.rb:253:in `block (2 levels) in spawn_rack_application'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/abstract_server_collection.rb:132:in `lookup_or_add'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/spawn_manager.rb:246:in `block in spawn_rack_application'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/abstract_server_collection.rb:82:in `block in synchronize'
  from Nginx/HelperAgent.cpp:584 time=2011-08-31 15:25:49.31 ]: Uncaught exception in PassengerServer client thread:
   exception: Cannot read response from backend process: Connection reset by peer (104)
   backtrace:
     in 'void Client::forwardResponse(Passenger::SessionPtr&,const Passenger::AnalyticsLogPtr&)' (HelperAgent.cpp:330)
     in 'void Client::handleRequest(Passenger::FileDescriptor&)' (HelperAgent.cpp:510)
     in 'void Client::threadMain()' (HelperAgent.cpp:603)

2011/08/31 15:25:49 [error] 21197#0: *41172 upstream prematurely closed connection while reading response header from upstream,host: "yandex.ru"
[ pid=21257 thr=15884760 file=utils.rb:176 time=2011-08-31 15:25:49.032 ]: *** Exception PGError in application (server closed the connection unexpectedly
  This probably means the server terminated abnormally
  before or while processing the request.
) (process 21257,thread #sql_adapter.rb:276:in `exec'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/postgresql_adapter.rb:276:in `block in clear_cache!'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/postgresql_adapter.rb:275:in `each_value'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/postgresql_adapter.rb:275:in `clear_cache!'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/postgresql_adapter.rb:303:in `disconnect!'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:202:in `block in disconnect!'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:201:in `each'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:201:in `disconnect!'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activesupport-3.1.0/lib/active_support/core_ext/module/synchronization.rb:35:in `block in disconnect_with_synchronization!'
  from /home/deployer/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/monitor.rb:201:in `mon_synchronize'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activesupport-3.1.0/lib/active_support/core_ext/module/synchronization.rb:34:in `disconnect_with_synchronization!'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:395:in `block in clear_all_connections!'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:395:in `each_value'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:395:in `clear_all_connections!'
  from /home/deployer/yandex.ru/shared/bundle/ruby/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/abstract/connection_specification.rb:123:in `clear_all_connections!'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/utils.rb:398:in `before_handling_requests'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/rack/application_spawner.rb:204:in `start_request_handler'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/rack/application_spawner.rb:170:in `block in handle_spawn_application'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/utils.rb:479:in `safe_fork'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/rack/application_spawner.rb:165:in `handle_spawn_application'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/abstract_server.rb:357:in `server_main_loop'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/abstract_server.rb:206:in `start_synchronously'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/abstract_server.rb:180:in `start'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/rack/application_spawner.rb:128:in `start'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/spawn_manager.rb:253:in `block (2 levels) in spawn_rack_application'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/abstract_server_collection.rb:132:in `lookup_or_add'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/spawn_manager.rb:246:in `block in spawn_rack_application'
  from /home/deployer/.rvm/gems/ruby-1.9.2-p180/gems/passenger-3.0.7/lib/phusion_passenger/abstract_server_collection.rb:82:in `block in synchronize'
  from