[Docker]多数ゲストOS上のservice mysqld startが[FAILED]になるときの対処法

１つのホストに多数のゲストOS(コンテナ)を立ち上げて、それぞれでservice mysqld startをやると、何度やってもあるところから失敗することがある。
(自分の場合は24個目のコンテナ以降すべて失敗した)

# service mysqld start
Starting mysqld (via systemctl):  Job for mysqld.service failed because the control process exited with error code. See "systemctl status mysqld.service" and "journalctl -xe" for details.
                                                           [FAILED]

毎回失敗する場所が同じなので、おそらく何かのしきい値が低いとかだと思った。

まずログを見てみる。

/var/log/mysqld.log

2017-07-26 14:40:09 333 [Note] Plugin 'FEDERATED' is disabled.
2017-07-26 14:40:09 333 [Note] InnoDB: Using atomics to ref count buffer pool pages
2017-07-26 14:40:09 333 [Note] InnoDB: The InnoDB memory heap is disabled
2017-07-26 14:40:09 333 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2017-07-26 14:40:09 333 [Note] InnoDB: Memory barrier is not used
2017-07-26 14:40:09 333 [Note] InnoDB: Compressed tables use zlib 1.2.3
2017-07-26 14:40:09 333 [Note] InnoDB: Using Linux native AIO
2017-07-26 14:40:09 333 [Note] InnoDB: Not using CPU crc32 instructions
2017-07-26 14:40:09 7f97ece2c740 InnoDB: Warning: io_setup() failed with EAGAIN. Will make 5 attempts before giving up.
InnoDB: Warning: io_setup() attempt 1 failed.
InnoDB: Warning: io_setup() attempt 2 failed.
InnoDB: Warning: io_setup() attempt 3 failed.
InnoDB: Warning: io_setup() attempt 4 failed.
InnoDB: Warning: io_setup() attempt 5 failed.
2017-07-26 14:40:12 7f97ece2c740 InnoDB: Error: io_setup() failed with EAGAIN after 5 attempts.
InnoDB: You can disable Linux Native AIO by setting innodb_use_native_aio = 0 in my.cnf
2017-07-26 14:40:12 333 [ERROR] InnoDB: Fatal : Cannot initialize AIO sub-system
2017-07-26 14:40:12 333 [ERROR] Plugin 'InnoDB' init function returned error.
2017-07-26 14:40:12 333 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
2017-07-26 14:40:12 333 [ERROR] Unknown/unsupported storage engine: InnoDB
2017-07-26 14:40:12 333 [ERROR] Aborting


(略)

You can disable Linux Native AIO by setting innodb_use_native_aio = 0 in my.cnf
と言うとおり、my.cnfにinnodb_use_native_aio = 0を追記してみたが変わらず。

結果を言うと、ホストの/proc/sys/fs/aio-max-nrの値が低すぎるということみたい。
適当な大きい値を上記ファイルに入れてみる。

echo 500000 > /proc/sys/fs/aio-max-nr

これでゲストOSでmysqldをstartできました。