独角兽吞噬MySQL连接不尊重池大小-Rails

Question

我为Rails应用程序运行了4个Unicorn进程，它们耗尽了所有可用的MySQL连接，导致其崩溃，出现“连接太多”错误。今天我不得不重新启动我的DB实例4次=(

过程

$ ps ax | grep [u]ni
21618 ?        Sl     0:15 unicorn master -D -c /home/deployer/apps/XXX/shared/config/unicorn.rb -E production                                                           
21632 ?        Sl     0:20 unicorn worker[0] -D -c /home/deployer/apps/XXX/shared/config/unicorn.rb -E production                                                        
21636 ?        Sl     0:14 unicorn worker[1] -D -c /home/deployer/apps/XXX/shared/config/unicorn.rb -E production                                                        
21640 ?        Sl     0:20 unicorn worker[2] -D -c /home/deployer/apps/XXX/shared/config/unicorn.rb -E production                                                        
21645 ?        Sl     0:12 unicorn worker[3] -D -c /home/deployer/apps/XXX/shared/config/unicorn.rb -E production  

我的database.yml正在为ActiveRecords池设置22个连接...

...
production:
  adapter: mysql2
  encoding: utf8
  database: xxx
  username: xxx
  password: xxx
  host: xxx
  port: 3306
  pool: 22
...

Unicorn配置文件如下所示：

working_directory "/home/deployer/apps/XXX/current"
pid "/home/deployer/apps/XXX/shared/pids/unicorn.pid"
stderr_path "/home/deployer/apps/XXX/shared/log/unicorn.log"
stdout_path "/home/deployer/apps/XXX/shared/log/unicorn.log"

listen "/tmp/unicorn.XXX.sock"
worker_processes 4
timeout 100

preload_app true

before_fork do |server, worker|
  # Disconnect since the database connection will not carry over
  if defined? ActiveRecord::Base
    ActiveRecord::Base.connection.disconnect!
  end

  # Quit the old unicorn process
  old_pid = "#{server.config[:pid]}.oldbin"
  if File.exists?(old_pid) && server.pid != old_pid
    begin
      Process.kill("QUIT", File.read(old_pid).to_i)
    rescue Errno::ENOENT, Errno::ESRCH
      # someone else did our job for us
    end
  end
end

after_fork do |server, worker|
  # Start up the database connection again in the worker
  if defined?(ActiveRecord::Base)
    ActiveRecord::Base.establish_connection
  end
  child_pid = server.config[:pid].sub(".pid", ".#{worker.nr}.pid")
  system("echo #{Process.pid} > #{child_pid}")
end

如果我们查看数据库控制台，我们会看到这样的情况。他们已经吃掉了大部分连接。（我现在除了独角兽运行什么都没有）在我看来，应该有1个连接*4个独角兽=4个连接。

mysql> show full processlist;
+-----+----------+--------------------------------------------------+------------------------+---------+------+-------+-----------------------+
| Id  | User     | Host                                             | db                     | Command | Time | State | Info                  |
+-----+----------+--------------------------------------------------+------------------------+---------+------+-------+-----------------------+
|   2 | rdsadmin | localhost:31383                                  | NULL                   | Sleep   |    9 |       | NULL                  |
|  52 | level    | 212.100.140.42:50683                             | leveltravel_production | Query   |    0 | NULL  | show full processlist |
|  74 | level    | ip-10-55-10-151.eu-west-1.compute.internal:38197 | leveltravel_production | Sleep   |    5 |       | NULL                  |
|  75 | level    | ip-10-55-10-151.eu-west-1.compute.internal:38199 | leveltravel_production | Sleep   |    8 |       | NULL                  |
|  76 | level    | ip-10-55-10-151.eu-west-1.compute.internal:38201 | leveltravel_production | Sleep   |    8 |       | NULL                  |

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ CUT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

| 157 | level    | ip-10-55-10-151.eu-west-1.compute.internal:38321 | leveltravel_production | Sleep   |  154 |       | NULL                  |
| 158 | level    | ip-10-55-10-151.eu-west-1.compute.internal:38322 | leveltravel_production | Sleep   |   17 |       | NULL                  |
| 159 | level    | ip-10-55-10-151.eu-west-1.compute.internal:38325 | leveltravel_production | Sleep   |   54 |       | NULL                  |
| 160 | level    | ip-10-55-10-151.eu-west-1.compute.internal:38326 | leveltravel_production | Sleep   |   54 |       | NULL                  |
| 161 | level    | ip-10-55-10-151.eu-west-1.compute.internal:38327 | leveltravel_production | Sleep   |   54 |       | NULL                  |
| 162 | level    | ip-10-55-10-151.eu-west-1.compute.internal:38329 | leveltravel_production | Sleep   |   42 |       | NULL                  |
+-----+----------+--------------------------------------------------+------------------------+---------+------+-------+-----------------------+
90 rows in set (0.15 sec)

您还可以查看sidekiq存储库中的问题503，了解此问题的背景https://github.com/mperham/sidekiq/issues/503

Answer 1

您已经运行了4个unicorn进程。这是过程，而不是线程
池中每个进程有22个连接。总共有22个*4=88个连接
若要为4个工作进程建立4个连接，可以在数据库中设置池：1。yml公司