This happened on Centos for no apparent reason with no obvious issue in the logs. Data could be read fine but not written (possibly due to some corruption or out of memory issue in the OpenVZ container is the best guess).
All mysql update and insert queries failed freezing without any error log on any database and table.
Tried to restart:
service mysqld restart
Timeout error occurred trying to stop MySQL Daemon.
Stopping mysqld: [FAILED]
MySQL Daemon failed to start.
Starting mysqld: [FAILED]
#manually kill mysqld and mysqld_safe
ps aux|grep mysqld
root 876 0.0 0.0 3732 584 ? S 2017 0:00 /bin/sh /usr/bin/mysqld_safe --datadir=/var/lib/mysql --socket=/var/lib/mysql/mysql.sock --pid-file=/var/run/mysqld/mysqld.pid --basedir=/usr --user=mysql
mysql 1322 2.3 4.2 484384 269240 ? Sl 2017 12779:34 /usr/libexec/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib/mysql/plugin --user=mysql --log-error=/var/log/mysqld.log --pid-file=/var/run/mysqld/mysqld.pid --socket=/var/lib/mysql/mysql.sock
root 2423 0.0 0.0 2360 692 pts/2 S+ 13:28 0:00 grep mysqld
After manually killing everything seemed to work OK after that point.
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