MySql crashes on Ubuntu 16.04 using WordPress

Hello,

I have an issue right now with my Server Ubuntu 16.04 and I was hoping someone could help or guide me to the solution. I recently installed Wordpress and it worked fine for 3 days but now it is displaying the following error: “Error establishing a database connection”. It always crashes for a couple of seconds and then it works again, but this keeps happening all the time. So I collected the logs for Mysql and I found this:

<^>2018-01-26T04:01:17.405635Z 0 [ERROR] InnoDB: mmap(137428992 bytes) failed; errno 12 2018-01-26T04:01:17.405656Z 0 [ERROR] InnoDB: Cannot allocate memory for the buffer pool 2018-01-26T04:01:17.405666Z 0 [ERROR] InnoDB: Plugin initialization aborted with error Generic error 2018-01-26T04:01:17.405676Z 0 [ERROR] Plugin ‘InnoDB’ init function returned error. 2018-01-26T04:01:17.405683Z 0 [ERROR] Plugin ‘InnoDB’ registration as a STORAGE ENGINE failed. 2018-01-26T04:01:17.405691Z 0 [ERROR] Failed to initialize builtin plugins. 2018-01-26T04:01:17.405697Z 0 [ERROR] Aborting

2018-01-26T04:01:17.405712Z 0 [Note] Binlog end 2018-01-26T04:01:17.408006Z 0 [Note] /usr/sbin/mysqld: Shutdown complete

2018-01-26T04:01:47.308940Z 0 [Warning] Changed limits: max_open_files: 1024 (requested 5000) 2018-01-26T04:01:47.308976Z 0 [Warning] Changed limits: table_open_cache: 431 (requested 2000) 2018-01-26T04:01:47.467060Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_def aults_for_timestamp server option (see documentation for more details). 2018-01-26T04:01:47.468608Z 0 [Note] /usr/sbin/mysqld (mysqld 5.7.21-0ubuntu0.16.04.1) starting as process 5600 … 2018-01-26T04:01:47.472435Z 0 [Note] InnoDB: PUNCH HOLE support available 2018-01-26T04:01:47.472454Z 0 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins 2018-01-26T04:01:47.472458Z 0 [Note] InnoDB: Uses event mutexes 2018-01-26T04:01:47.472462Z 0 [Note] InnoDB: GCC builtin __atomic_thread_fence() is used for memory barrier 2018-01-26T04:01:47.472478Z 0 [Note] InnoDB: Compressed tables use zlib 1.2.8 2018-01-26T04:01:47.472481Z 0 [Note] InnoDB: Using Linux native AIO 2018-01-26T04:01:47.472701Z 0 [Note] InnoDB: Number of pools: 1 2018-01-26T04:01:47.472810Z 0 [Note] InnoDB: Using CPU crc32 instructions 2018-01-26T04:01:47.474205Z 0 [Note] InnoDB: Initializing buffer pool, total size = 128M, instances = 1, chunk size = 128M 2018-01-26T04:01:47.482501Z 0 [Note] InnoDB: Completed initialization of buffer pool 2018-01-26T04:01:47.484835Z 0 [Note] InnoDB: If the mysqld execution user is authorized, page cleaner thread priority can be changed. See the man page of setpriority(). 2018-01-26T04:01:47.504123Z 0 [Note] InnoDB: Highest supported file format is Barracuda. 2018-01-26T04:01:47.506227Z 0 [Note] InnoDB: Log scan progressed past the checkpoint lsn 28060943 2018-01-26T04:01:47.506240Z 0 [Note] InnoDB: Doing recovery: scanned up to log sequence number 28060952 2018-01-26T04:01:47.506244Z 0 [Note] InnoDB: Database was not shutdown normally! 2018-01-26T04:01:47.506248Z 0 [Note] InnoDB: Starting crash recovery. 2018-01-26T04:01:47.689508Z 0 [Note] InnoDB: Removed temporary tablespace data file: “ibtmp1” 2018-01-26T04:01:47.689526Z 0 [Note] InnoDB: Creating shared tablespace for temporary tables 2018-01-26T04:01:47.689556Z 0 [Note] InnoDB: Setting file ‘./ibtmp1’ size to 12 MB. Physically writing the file full; Please wait … 2018-01-26T04:01:47.725880Z 0 [Note] InnoDB: File ‘./ibtmp1’ size is now 12 MB. 2018-01-26T04:01:47.726525Z 0 [Note] InnoDB: 96 redo rollback segment(s) found. 96 redo rollback segment(s) are active . 2018-01-26T04:01:47.726535Z 0 [Note] InnoDB: 32 non-redo rollback segment(s) are active. 2018-01-26T04:01:47.726671Z 0 [Note] InnoDB: Waiting for purge to start 2018-01-26T04:01:47.776850Z 0 [Note] InnoDB: 5.7.21 started; log sequence number 28060952 2018-01-26T04:01:47.777089Z 0 [Note] InnoDB: Loading buffer pool(s) from /var/lib/mysql/ib_buffer_pool 2018-01-26T04:01:47.778297Z 0 [Note] Plugin ‘FEDERATED’ is disabled. 2018-01-26T04:01:47.787146Z 0 [Note] InnoDB: Buffer pool(s) load completed at 180126 4:01:47 2018-01-26T04:01:47.787636Z 0 [Warning] Failed to set up SSL because of the following SSL library error: SSL context i s not usable without certificate and private key 2018-01-26T04:01:47.825642Z 0 [Note] Event Scheduler: Loaded 0 events 2018-01-26T04:01:47.825743Z 0 [Note] /usr/sbin/mysqld: ready for connections. Version: ‘5.7.21-0ubuntu0.16.04.1’ socket: ‘/var/run/mysqld/mysqld.sock’ port: 3306 (Ubuntu) 2018-01-26T04:01:48.311112Z 2 [Note] Access denied for user ‘root’@‘localhost’ (using password: NO)<^>

I’m definitely not a server expert, but I will appreciate if someone could tell what this means, and what solutions should I try

Thank you!