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The system was running fine, but all of a sudden got this error 'Database connection failed', what might be the possible issues, how can I fix this error forever. Thank you.

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System Information: Ubuntu 16.04.3 x64 2 GB Memory / 50 GB Disk

I checked with 'df -h' in the terminal,

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I did error log check:

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2018-07-31T10:10:04.751870Z 0 [Note] /usr/sbin/mysqld: Shutdown complete

2018-07-31T10:10:34.438715Z 0 [Warning] Changed limits: max_open_files: 1024 (requested 5000)
2018-07-31T10:10:34.438807Z 0 [Warning] Changed limits: table_open_cache: 431 (requested 2000)
2018-07-31T10:10:34.613317Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2018-07-31T10:10:34.615293Z 0 [Note] /usr/sbin/mysqld (mysqld 5.7.23-0ubuntu0.16.04.1) starting as process 14674 ...
2018-07-31T10:10:34.620666Z 0 [Note] InnoDB: PUNCH HOLE support available
2018-07-31T10:10:34.620694Z 0 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2018-07-31T10:10:34.620699Z 0 [Note] InnoDB: Uses event mutexes
2018-07-31T10:10:34.620703Z 0 [Note] InnoDB: GCC builtin __atomic_thread_fence() is used for memory barrier
2018-07-31T10:10:34.620706Z 0 [Note] InnoDB: Compressed tables use zlib 1.2.8
2018-07-31T10:10:34.620710Z 0 [Note] InnoDB: Using Linux native AIO
2018-07-31T10:10:34.621008Z 0 [Note] InnoDB: Number of pools: 1
2018-07-31T10:10:34.621153Z 0 [Note] InnoDB: Using CPU crc32 instructions
2018-07-31T10:10:34.623069Z 0 [Note] InnoDB: Initializing buffer pool, total size = 128M, instances = 1, chunk size = 128M
2018-07-31T10:10:34.634597Z 0 [Note] InnoDB: Completed initialization of buffer pool
2018-07-31T10:10:34.637277Z 0 [Note] InnoDB: If the mysqld execution user is authorized, page cleaner thread priority can be changed. See the man page of setpriority().
2018-07-31T10:10:34.647303Z 0 [Note] InnoDB: The first innodb_system data file 'ibdata1' did not exist. A new tablespace will be created!
2018-07-31T10:10:34.647393Z 0 [ERROR] InnoDB: redo log file './ib_logfile0' exists. Creating system tablespace with existing redo log files is not recommended. Please delete all redo log files before creating new system tablespace.
2018-07-31T10:10:34.647403Z 0 [ERROR] InnoDB: InnoDB Database creation was aborted with error Generic error. You may need to delete the ibdata1 file before trying to start up again.
2018-07-31T10:10:35.248139Z 0 [ERROR] Plugin 'InnoDB' init function returned error.
2018-07-31T10:10:35.248186Z 0 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
2018-07-31T10:10:35.248195Z 0 [ERROR] Failed to initialize builtin plugins.
2018-07-31T10:10:35.248201Z 0 [ERROR] Aborting

2018-07-31T10:10:35.248222Z 0 [Note] Binlog end
2018-07-31T10:10:35.248304Z 0 [Note] Shutting down plugin 'MyISAM'
2018-07-31T10:10:35.248323Z 0 [Note] Shutting down plugin 'CSV'
2018-07-31T10:10:35.248824Z 0 [Note] /usr/sbin/mysqld: Shutdown complete
Dinesh Sunny
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3 Answers3

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Did you change ib_logfile size in the process? the error The first innodb_system data file 'ibdata1' did not exist. A new tablespace will be created! shows that it cannot find your ibdata file. Did you try the suggested Please delete all redo log files before creating new system tablespace?

Evgeniy Voevodin
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solved it by following these steps for the error:

InnoDB: Unable to lock ./ibdata1, error: 11

commands are:

# cd /var/lib/mysql
# mkdir bak
# mv ibdata1 bak/.
# mv ib_logfile* bak/.
# cp -a bak/ibdata1 ibdata1
# cp -a bak/ib_logfile* .
# service mysql restart

Read the source

and then I was getting the error regarding 'restarting mysql service'

find the error post here

and then followed these steps:

lsof -i:3306

Then kill it (the process number)

kill -9 PROCESS

e.g. kill -9 13498

Then try to restart MySQL again.

Read the Source

thanks to @Evgeniy and @Quiron.

Dinesh Sunny
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0

It should be helpfull if you tell us if your moodle is hosted using LAMP, a MAMP, a WAMP, a WIMP, a XAMPP, remote hosted...

Also if you check the error log it should have more info about the problem. I had the same error time ago, the DB was overloaded so changing the value of max_execution_time solved the error. Into config.php search:

upload_max_filesize = 2M or the value yo need.

max_execution_time = 60 or the value you need, the value are seconds.

After see your log I search for your error and I hope this will works:

Decrease the value of innodb-buffer-pool size in the config file/etc/mysql/my.cnf:

 
innodb_buffer_pool_size = 10M

After save my.cnf, restart mysql service.

SOURCE: Getting error "Plugin 'InnoDB' registration as a STORAGE ENGINE failed" when starting MySQL
Community
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Quiron
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  • I am using LAMP hosting, also please check now I have updated the error log. – Dinesh Sunny Jul 31 '18 at 10:23
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    thank you, added the innodb_buffer_pool_size = 10M line in the /etc/mysql/my.cnf and restarted gave this error, please find the error here. https://stackoverflow.com/q/51612113/2958795 – Dinesh Sunny Jul 31 '18 at 11:18