Ubuntu mysql stops working - mysql

Question

I am have vps setup with ubuntu 14 server. I have lamp stack installed. Everything works perfect but mysql server stops frequently and i have to restart it manually. Here is my my.cnf mysql config file.
# 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]
#
# * 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/
And following is my mysqltuner output.
-------- General Statistics ------------------------------------------------
[--] Skipped version check for MySQLTuner script
[OK] Currently running supported MySQL version 5.5.49-0ubuntu0.14.04.1
[OK] Operating on 64-bit architecture
-------- Storage Engine Statistics -------------------------------------------
[--] Status: +Archive -BDB -Federated +InnoDB -ISAM -NDBCluster
[--] Data in MyISAM tables: 38K (Tables: 34)
[--] Data in PERFORMANCE_SCHEMA tables: 0B (Tables: 17)
[--] Data in InnoDB tables: 11M (Tables: 101)
[!!] Total fragmented tables: 101
-------- Security Recommendations -------------------------------------------
[OK] All database users have passwords assigned
-------- Performance Metrics -------------------------------------------------
[--] Up for: 1h 13m 27s (2K q [0.464 qps], 130 conn, TX: 5M, RX: 332K)
[--] Reads / Writes: 81% / 19%
[--] Total buffers: 192.0M global + 2.7M per thread (151 max threads)
[!!] Maximum possible memory usage: 597.8M (121% of installed RAM)
[OK] Slow queries: 0% (0/2K)
[OK] Highest usage of available connections: 7% (12/151)
[OK] Key buffer size / total MyISAM indexes: 16.0M/196.0K
[OK] Query cache efficiency: 33.9% (493 cached / 1K selects)
[OK] Query cache prunes per day: 0
[OK] Sorts requiring temporary tables: 0% (0 temp sorts / 77 sorts)
[!!] Temporary tables created on disk: 33% (166 on disk / 498 total)
[OK] Thread cache hit rate: 90% (12 created / 130 connections)
[OK] Table cache hit rate: 94% (178 open / 189 opened)
[OK] Open file limit used: 11% (116/1K)
[OK] Table locks acquired immediately: 100% (1K immediate / 1K locks)
[OK] InnoDB data size / buffer pool: 11.9M/128.0M
-------- Recommendations -----------------------------------------------------
General recommendations:
Run OPTIMIZE TABLE to defragment tables for better performance
MySQL started within last 24 hours - recommendations may be inaccurate
Reduce your overall MySQL memory footprint for system stability
Enable the slow query log to troubleshoot bad queries
When making adjustments, make tmp_table_size/max_heap_table_size equal
Reduce your SELECT DISTINCT queries without LIMIT clauses
Variables to adjust:
*** MySQL's maximum memory usage is dangerously high ***
*** Add RAM before increasing MySQL buffer variables ***
tmp_table_size (> 16M)
max_heap_table_size (> 16M)
And here is my memory uses
Every 5.0s: free -m Sun Jul 3 03:12:12 2016
total used free shared buffers cached
Mem: 490 476 13 64 10 183
-/+ buffers/cache: 281 208
Swap: 0 0 0
What can be wrong here. Is there some misconfig on my my.cnf or something else is killing mysql. Please help me to find the issue.

Answer 1

Its possible that mysql runs out of memory. It happens when your system lacks swapping ( i.e. When memory gets exhausted, programs can't be transferred from main memory to a "swap" file in order to prevent system from memory failures ).
Swap explanation from Linux.com:
Linux divides its physical RAM (random access memory) into chucks of
memory called pages. Swapping is the process whereby a page of memory
is copied to the preconfigured space on the hard disk, called swap
space, to free up that page of memory. The combined sizes of the
physical memory and the swap space is the amount of virtual memory
available.
You can tweak "innodb_buffer_pool_size" to reduce indexing and caching footprints in the memory.
Ideally, you set the size of the buffer pool to as large a value as
practical, leaving enough memory for other processes on the server to
run without excessive paging. The larger the buffer pool, the more
InnoDB acts like an in-memory database, reading data from disk once
and then accessing the data from memory during subsequent reads.
Buffer pool size is configured using the innodb_buffer_pool_size
configuration option.
According to MySql documentation:
Solution:
Add this under [mysqld] : innodb_buffer_pool_size=64M
then make a swap file:
dd if=/dev/zero of=/swapfile bs=100M count=40
mkswap /swapfile
swapon /swapfile
and add this to /etc/fstab:
/swapfile none swap sw 0 0