I have a server ruing wordpress on it.
It is ruing well these days, but today I found it can not coect database.
So I checked server, found mysql service was shutdown.
Then I restart , but it only work for a while, after some seconds, it shutdown again.
This is mysql log:
160508 10:07:36 [Waing] IP address '222.186.59.174' could not be resolved: Name or service not known
160508 14:08:14 [Waing] IP address '210.209.127.33' could not be resolved: Name or service not known
160508 23:08:15 [Waing] IP address '183.63.89.196' could not be resolved: Name or service not known
160509 16:08:02 [Waing] IP address '198.55.114.190' has been resolved to the host name '198.55.114.190.static.quadranet.com', which resembles IPv4-address itself.
160510 8:30:34 [Waing] IP address '222.186.134.25' could not be resolved: Name or service not known
160510 12:39:02 [Waing] IP address '118.193.255.253' could not be resolved: Name or service not known
160510 16:06:36 [Waing] IP address '118.193.218.65' could not be resolved: Name or service not known
160511 0:02:03 [Waing] IP address '116.255.183.230' could not be resolved: Name or service not known
160511 00:39:09 mysqld_safe Number of processes ruing now: 0
160511 00:39:09 mysqld_safe mysqld restarted
160511 0:39:10 [Note] /usr/libexec/mysqld (mysqld 5.5.47-MariaDB) starting as process 24298 ...
160511 0:39:42 IoDB: The IoDB memory heap is disabled
160511 0:39:42 IoDB: Mutexes and rw_locks use GCC atomic builtins
160511 0:39:42 IoDB: Compressed tables use zlib 1.2.7
160511 0:39:42 IoDB: Using Linux native AIO
160511 0:39:42 IoDB: Initializing buffer pool, size = 128.0M
IoDB: mmap(137756672 bytes) failed; ero 12
160511 0:39:42 IoDB: Completed initialization of buffer pool
160511 0:39:42 IoDB: Fatal error: caot allocate memory for the buffer pool
160511 0:39:42 [ERROR] Plugin 'IoDB' init function retued error.
160511 0:39:42 [ERROR] Plugin 'IoDB' registration as a STORAGE ENGINE failed.
160511 0:39:42 [ERROR] mysqld: Out of memory (Needed 128917504 bytes)
160511 0:39:42 [ERROR] mysqld: Out of memory (Needed 96681984 bytes)
160511 0:39:42 [ERROR] mysqld: Out of memory (Needed 72499200 bytes)
160511 00:39:44 mysqld_safe mysqld from pid file /var/run/mariadb/mariadb.pid ended
160511 17:11:08 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
160511 17:11:08 [Note] /usr/libexec/mysqld (mysqld 5.5.47-MariaDB) starting as process 24894 ...
160511 17:11:08 IoDB: The IoDB memory heap is disabled
160511 17:11:08 IoDB: Mutexes and rw_locks use GCC atomic builtins
160511 17:11:08 IoDB: Compressed tables use zlib 1.2.7
160511 17:11:08 IoDB: Using Linux native AIO
160511 17:11:08 IoDB: Initializing buffer pool, size = 128.0M
160511 17:11:08 IoDB: Completed initialization of buffer pool
160511 17:11:08 IoDB: highest supported file format is Barracuda.
IoDB: The log sequence number in ibdata files does not match
IoDB: the log sequence number in the ib_logfiles!
160511 17:11:08 IoDB: Database was not shut down normally!
IoDB: Starting crash recovery.
IoDB: Reading tablespace information from the .ibd files...
IoDB: Restoring possible half-written data pages from the doublewrite
IoDB: buffer...
160511 17:11:08 IoDB: Waiting for the background threads to start
160511 17:11:09 Percona XtraDB (http://www.percona.com) 5.5.46-MariaDB-37.6 started; log sequence number 8239814
160511 17:11:09 [Note] Plugin 'FEEDBACK' is disabled.
160511 17:11:09 [Note] Server socket created on IP: '0.0.0.0'.
160511 17:11:09 [Note] Event Scheduler: Loaded 0 events
160511 17:11:09 [Note] /usr/libexec/mysqld: ready for coections.
Version: '5.5.47-MariaDB' socket: '/var/lib/mysql/mysql.sock' port: 3306 MariaDB Server
160511 17:12:21 mysqld_safe Number of processes ruing now: 0
160511 17:12:21 mysqld_safe mysqld restarted
160511 17:12:21 [Note] /usr/libexec/mysqld (mysqld 5.5.47-MariaDB) starting as process 25104 ...
160511 17:12:21 IoDB: The IoDB memory heap is disabled
160511 17:12:21 IoDB: Mutexes and rw_locks use GCC atomic builtins
160511 17:12:21 IoDB: Compressed tables use zlib 1.2.7
160511 17:12:21 IoDB: Using Linux native AIO
160511 17:12:21 IoDB: Initializing buffer pool, size = 128.0M
IoDB: mmap(137756672 bytes) failed; ero 12
160511 17:12:21 IoDB: Completed initialization of buffer pool
160511 17:12:21 IoDB: Fatal error: caot allocate memory for the buffer pool
160511 17:12:21 [ERROR] Plugin 'IoDB' init function retued error.
160511 17:12:21 [ERROR] Plugin 'IoDB' registration as a STORAGE ENGINE failed.
160511 17:12:21 [ERROR] mysqld: Out of memory (Needed 128917504 bytes)
160511 17:12:21 [ERROR] mysqld: Out of memory (Needed 96681984 bytes)
160511 17:12:21 [ERROR] mysqld: Out of memory (Needed 72499200 bytes)
160511 17:12:21 [Note] Plugin 'FEEDBACK' is disabled.
160511 17:12:21 [ERROR] Unknown/unsupported storage engine: IoDB
160511 17:12:21 [ERROR] Aborting
160511 17:12:21 [Note] /usr/libexec/mysqld: Shutdown complete
160511 17:12:21 mysqld_safe mysqld from pid file /var/run/mariadb/mariadb.pid ended
I always see there are a lot failed login attempt when I ssh to my server, and you can see there are many ip in log, is attackers caused this problem or my server has been attacked? ?
If not, what happend to my server?