Rails的失去連接到MySQL

Question

在做正常的數據庫查詢與ActiveRecord的我遇到以下錯誤：

Mysql2::Error: Lost connection to MySQL server during query

甚至

ActiveRecord::StatementInvalid (Mysql2::Error: MySQL client ran out of memory)

的錯誤是不可恢復（重新連接可以通過唯一的應用程序重新啓動），並且不綁定到特定的數據庫查詢（它們在各種應用程序中突然彈出）。

該應用程序不是高負載的。其實我是它的唯一用戶。

有時應用程序運行一整夜沒有任何問題，有時它會在幾小時/分鐘的操作後崩潰。有時WEBrick/Puma會突然退出，並退出一些沒有任何MySQL錯誤的代碼。

我試圖將Rails從4.0.4升級到更高版本，試圖將MySQL從5.6降級到5.5，試圖更改mysql2 gem版本 - 沒有任何幫助。

1. 它不能成爲網絡連接問題，因爲MySQL運行在同一臺機器上，並且通過本地主機名訪問。

2. 數據庫不存儲數百萬行，並且沒有查詢返回重複的行。

3. 我不確定初始連接，因爲我真的不知道Rails是否重複使用現有連接進行多個查詢或爲每個查詢創建新連接。它不能是長途或慢速連接，因爲它是本地主機。

問題：

1. 我是怎麼碰上的情況呢？

2. 如何解決問題？

這裏是一塊日誌：

在不同的線程

Driver Load (0.0ms) SELECT `drivers`.* FROM `drivers` WHERE `drivers`.`ts_id` = 1 
    WorkShift Load (1.0ms) SELECT `work_shifts`.* FROM `work_shifts` WHERE `work_shifts`.`driver_id` = 1 AND `work_shifts`.`current_state` = 1 ORDER BY `work_shifts`.`scheduled_opened_at` DESC LIMIT 1 
    Trip Load (1.0ms) SELECT `trips`.* FROM `trips` WHERE `trips`.`work_shift_id` = 1 AND (current_state in (3,4,5,9)) ORDER BY `trips`.`id` ASC LIMIT 1 
Mysql2::Error: Lost connection to MySQL server during query: SELECT `trips`.* FROM `trips` WHERE `trips`.`work_shift_id` = 1 AND (current_state in (3,4,5,9)) ORDER BY `trips`.`id` ASC LIMIT 1 
2014-10-11 22:56:30 UpCloud(1).send_driver_statuses: Exception(ActiveRecord::StatementInvalid): Mysql2::Error: Lost connection to MySQL server during query: SELECT `trips`.* FROM `trips` WHERE `trips`.`work_shift_id` = 1 AND (current_state in (3,4,5,9)) ORDER BY `trips`.`id` ASC LIMIT 1 

==== Stack trace: ==== 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:287:in `query' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:287:in `block in execute' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/abstract_adapter.rb:442:in `block in log' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activesupport-4.0.4/lib/active_support/notifications/instrumenter.rb:20:in `instrument' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/abstract_adapter.rb:437:in `log' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:287:in `execute' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/mysql2_adapter.rb:222:in `execute' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/mysql2_adapter.rb:226:in `exec_query' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/mysql2_adapter.rb:235:in `select' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/abstract/database_statements.rb:32:in `select_all' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/abstract/query_cache.rb:63:in `select_all' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/querying.rb:36:in `find_by_sql' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/relation.rb:585:in `exec_queries' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/association_relation.rb:15:in `exec_queries' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/relation.rb:471:in `load' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/relation.rb:220:in `to_a' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/relation/finder_methods.rb:326:in `find_first' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/relation/finder_methods.rb:91:in `first' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-deprecated_finders-1.0.3/lib/active_record/deprecated_finders/relation.rb:129:in `first' 
D:/Work/disp/lib/ex/up_cloud.rb:365:in `up_driver_status' 
D:/Work/disp/lib/ex/up_cloud.rb:416:in `block (4 levels) in send_driver_statuses' 
C:in `each' 
C:in `each' 
D:/Work/disp/lib/ex/up_cloud.rb:415:in `block (3 levels) in send_driver_statuses' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/nokogiri-1.6.3.1-x86-mingw32/lib/nokogiri/xml/builder.rb:391:in `call' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/nokogiri-1.6.3.1-x86-mingw32/lib/nokogiri/xml/builder.rb:391:in `insert' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/nokogiri-1.6.3.1-x86-mingw32/lib/nokogiri/xml/builder.rb:375:in `method_missing' 
D:/Work/disp/lib/ex/up_cloud.rb:414:in `block (2 levels) in send_driver_statuses' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/nokogiri-1.6.3.1-x86-mingw32/lib/nokogiri/xml/builder.rb:391:in `call' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/nokogiri-1.6.3.1-x86-mingw32/lib/nokogiri/xml/builder.rb:391:in `insert' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/nokogiri-1.6.3.1-x86-mingw32/lib/nokogiri/xml/builder.rb:375:in `method_missing' 
D:/Work/disp/lib/ex/up_cloud.rb:413:in `block in send_driver_statuses' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/nokogiri-1.6.3.1-x86-mingw32/lib/nokogiri/xml/builder.rb:293:in `initialize' 
D:/Work/disp/lib/ex/up_cloud.rb:412:in `new' 
D:/Work/disp/lib/ex/up_cloud.rb:412:in `send_driver_statuses' 
D:/Work/disp/lib/ex/up_cloud.rb:73:in `block in initialize' 
    Driver Load (1.0ms) SELECT drivers.id, work_shifts.latitude, work_shifts.longitude, work_shifts.updated_at FROM `drivers` INNER JOIN `work_shifts` ON `work_shifts`.`driver_id` = `drivers`.`id` WHERE `drivers`.`ts_id` = 1 AND `work_shifts`.`current_state` = 1 
Mysql2::Error: MySQL client ran out of memory: SELECT `orders`.* FROM `orders` WHERE `orders`.`current_state` = 2 
2014-10-11 22:56:32 Postman.postman thread: Exception(ActiveRecord::StatementInvalid): Mysql2::Error: MySQL client ran out of memory: SELECT `orders`.* FROM `orders` WHERE `orders`.`current_state` = 2 

==== Stack trace: ==== 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:287:in `query' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:287:in `block in execute' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/abstract_adapter.rb:442:in `block in log' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activesupport-4.0.4/lib/active_support/notifications/instrumenter.rb:20:in `instrument' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/abstract_adapter.rb:437:in `log' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:287:in `execute' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/mysql2_adapter.rb:222:in `execute' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/mysql2_adapter.rb:226:in `exec_query' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/mysql2_adapter.rb:235:in `select' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/abstract/database_statements.rb:32:in `select_all' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/connection_adapters/abstract/query_cache.rb:63:in `select_all' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/querying.rb:36:in `find_by_sql' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/relation.rb:585:in `exec_queries' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/relation.rb:471:in `load' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/relation.rb:220:in `to_a' 
C:/Ruby200/lib/ruby/gems/2.0.0/gems/activerecord-4.0.4/lib/active_record/relation.rb:565:in `blank?' 
D:/Work/disp/lib/postman.rb:31:in `do_posting' 
D:/Work/disp/lib/postman.rb:16:in `block (2 levels) in initialize' 
D:/Work/disp/lib/advanced_logging.rb:8:in `with_level' 
D:/Work/disp/lib/postman.rb:15:in `block in initialize' 

Answer 1

這個問題是執行數據庫查詢沒有適當的線程同步。