Erro ao estabelecer uma conexão com o banco de dados

Question

temos o site wordpress & todos os dias estamos ficando abaixo do erro:

erro ao estabelecer uma conexão com o banco de dados quase uma vez por dia

do que temos que reiniciar o servidor mysql para corrigir isso ....

var / log / mysql / mysql.log :

180420 15:00:33 [Warning] Using unique option prefix myisam-recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
180420 15:00:33 [Note] Plugin 'FEDERATED' is disabled.
180420 15:00:33 InnoDB: The InnoDB memory heap is disabled
180420 15:00:33 InnoDB: Mutexes and rw_locks use GCC atomic builtins
180420 15:00:33 InnoDB: Compressed tables use zlib 1.2.8
180420 15:00:33 InnoDB: Using Linux native AIO
180420 15:00:33 InnoDB: Initializing buffer pool, size = 64.0M
180420 15:00:33 InnoDB: Completed initialization of buffer pool
180420 15:00:33 InnoDB: highest supported file format is Barracuda.
InnoDB: The log sequence number in ibdata files does not match
InnoDB: the log sequence number in the ib_logfiles!
180420 15:00:33  InnoDB: Database was not shut down normally!
InnoDB: Starting crash recovery.
InnoDB: Reading tablespace information from the .ibd files...
InnoDB: Restoring possible half-written data pages from the doublewrite
InnoDB: buffer...
180420 15:00:33  InnoDB: Waiting for the background threads to start
180420 15:00:34 InnoDB: 5.5.40 started; log sequence number 95113383371
180420 15:00:34 [Note] Server hostname (bind-address): '127.0.0.1'; port: 3306
180420 15:00:34 [Note]   - '127.0.0.1' resolves to '127.0.0.1';
180420 15:00:34 [Note] Server socket created on IP: '127.0.0.1'.
180420 15:00:34 [Note] Event Scheduler: Loaded 0 events
180420 15:00:34 [Note] /usr/sbin/mysqld: ready for connections.
Version: '5.5.40-0ubuntu1'  socket: '/var/run/mysqld/mysqld.sock'  port: 3306  (Ubuntu)

/ etc / mysql - my.cnf

#
# The MySQL database server configuration file.
#
# You can copy this to one of:
# - "/etc/mysql/my.cnf" to set global options,
# - "~/.my.cnf" to set user-specific options.
# 
# One can use all long options that the program supports.
# Run program with --help to get a list of available options and with
# --print-defaults to see which it would actually understand and use.
#
# For explanations see
# http://dev.mysql.com/doc/mysql/en/server-system-variables.html

# This will be passed to all mysql clients
# It has been reported that passwords should be enclosed with ticks/quotes
# escpecially if they contain "#" chars...
# Remember to edit /etc/mysql/debian.cnf when changing the socket location.
[client]
port        = 3306
socket      = /var/run/mysqld/mysqld.sock

# Here is entries for some specific programs
# The following values assume you have at least 32M ram

# This was formally known as [safe_mysqld]. Both versions are currently parsed.
[mysqld_safe]
socket      = /var/run/mysqld/mysqld.sock
nice        = 0

[mysqld]
innodb_buffer_pool_size=64M
#
# * Basic Settings
#
user        = mysql
pid-file    = /var/run/mysqld/mysqld.pid
socket      = /var/run/mysqld/mysqld.sock
port        = 3306
basedir     = /usr
datadir     = /var/lib/mysql
tmpdir      = /tmp
lc-messages-dir = /usr/share/mysql
skip-external-locking
#
# Instead of skip-networking the default is now to listen only on
# localhost which is more compatible and is not less secure.
bind-address        = 127.0.0.1
#
# * Fine Tuning
#
key_buffer      = 16M
max_allowed_packet  = 16M
thread_stack        = 192K
thread_cache_size       = 8
# This replaces the startup script and checks MyISAM tables if needed
# the first time they are touched
myisam-recover         = BACKUP
#max_connections        = 100
#table_cache            = 64
#thread_concurrency     = 10
#
# * Query Cache Configuration
#
query_cache_limit   = 1M
query_cache_size        = 16M
#
# * Logging and Replication
#
# Both location gets rotated by the cronjob.
# Be aware that this log type is a performance killer.
# As of 5.1 you can enable the log at runtime!
#general_log_file        = /var/log/mysql/mysql.log
#general_log             = 1
#
# Error log - should be very few entries.
#
log_error = /var/log/mysql/error.log
#
# Here you can see queries with especially long duration
#log_slow_queries   = /var/log/mysql/mysql-slow.log
#long_query_time = 2
#log-queries-not-using-indexes
#
# The following can be used as easy to replay backup logs or for replication.
# note: if you are setting up a replication slave, see README.Debian about
#       other settings you may need to change.
#server-id      = 1
#log_bin            = /var/log/mysql/mysql-bin.log
expire_logs_days    = 10
max_binlog_size         = 100M
#binlog_do_db       = include_database_name
#binlog_ignore_db   = include_database_name
#
# * InnoDB
#
# InnoDB is enabled by default with a 10MB datafile in /var/lib/mysql/.
# Read the manual for more InnoDB related options. There are many!
#
# * Security Features
#
# Read the manual, too, if you want chroot!
# chroot = /var/lib/mysql/
#
# For generating SSL certificates I recommend the OpenSSL GUI "tinyca".
#
# ssl-ca=/etc/mysql/cacert.pem
# ssl-cert=/etc/mysql/server-cert.pem
# ssl-key=/etc/mysql/server-key.pem



[mysqldump]
quick
quote-names
max_allowed_packet  = 16M

[mysql]
#no-auto-rehash # faster start of mysql but no tab completition

[isamchk]
key_buffer      = 16M

#
# * IMPORTANT: Additional settings that can override those from this file!
#   The files must end with '.cnf', otherwise they'll be ignored.
#
!includedir /etc/mysql/conf.d/

quando eu corri o comando: zgrep -a "allocate memory" /var/log/mysql/error.log* , eu fiquei abaixo do resultado:

Tambémcorrifree-m:

mpm_prefork.conf

<IfModulempm_prefork_module>StartServers5MinSpareServers5MaxSpareServers10#MaxRequestWorkers150MaxRequestWorkers256MaxConnectionsPerChild500#MaxConnectionsPerChild0</IfModule>#vim:syntax=apachets=4sw=4sts=4srnoet

Resultado

cat/proc/meminfo: