Rails的失去连接到MySQL

Question

在做正常的数据库查询与ActiveRecord的我遇到以下错误：

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

甚至

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

的错误是不可恢复（重新连接可以通过唯一的应用程序重新启动），并且不绑定到特定的数据库查询（它们在各种应用程序中突然弹出）。

该应用程序不是高负载的。其实我是它的唯一用户。

有时应用程序运行一整夜没有任何问题，有时它会在几小时/分钟的操作后崩溃。有时WEBrick/Puma会突然退出，并退出一些没有任何MySQL错误的代码。

我试图将Rails从4.0.4升级到更高版本，试图将MySQL从5.6降级到5.5，试图更改mysql2 gem版本 - 没有任何帮助。

1. 它不能成为网络连接问题，因为MySQL运行在同一台机器上，并且通过本地主机名访问。

2. 数据库不存储数百万行，并且没有查询返回重复的行。

3. 我不确定初始连接，因为我真的不知道Rails是否重复使用现有连接进行多个查询或为每个查询创建新连接。它不能是长途或慢速连接，因为它是本地主机。

问题：

1. 我是怎么碰上的情况呢？

2. 如何解决问题？

这里是一块日志：

在不同的线程

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

这个问题是执行数据库查询没有适当的线程同步。