** Also affects: mysql-5.7 (Ubuntu Artful)
Importance: Undecided
Status: Confirmed
** Also affects: mysql-5.7 (Ubuntu Xenial)
Importance: Undecided
Status: New
** Also affects: mysql-5.7 (Ubuntu Zesty)
Importance: Undecided
Status: New
** Tags added: sts
** Changed in: mysql-5.7 (Ubuntu Artful)
Assignee: (unassigned) => Mario Splivalo (mariosplivalo)
** Changed in: mysql-5.7 (Ubuntu Zesty)
Assignee: (unassigned) => Mario Splivalo (mariosplivalo)
** Changed in: mysql-5.7 (Ubuntu Xenial)
Assignee: (unassigned) => Mario Splivalo (mariosplivalo)
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Matching subscriptions: Ubuntu 16.04 Bugs
https://bugs.launchpad.net/bugs/1721546
Title:
max open files limit prevents max_connections over 214 on systemd
Status in mysql-5.7 package in Ubuntu:
Confirmed
Status in mysql-5.7 source package in Xenial:
New
Status in mysql-5.7 source package in Zesty:
New
Status in mysql-5.7 source package in Artful:
Confirmed
Bug description:
With the default mysql-server installation on systemd versions of
Ubuntu (xenial and above) setting max_connections to more than 214
will not work, due to systemd imposed limits:
root@juju-c2777d-default-1:~# grep max_connections
/etc/mysql/mysql.conf.d/mysqld_settings_charm.cnf
max_connections = 5500
root@juju-c2777d-default-1:~# grep max_connections /var/log/mysql/error.log
2017-10-05T12:41:16.958726Z 0 [Warning] Changed limits: max_connections: 214
(requested 5500)
2017-10-05T12:41:19.198391Z 0 [Warning] Changed limits: max_connections: 214
(requested 5500)
root@juju-c2777d-default-1:~# grep open_files /var/log/mysql/error.log
2017-10-05T12:41:11.824199Z 0 [Warning] Changed limits: max_open_files: 1024
(requested 5000)
2017-10-05T12:41:16.958668Z 0 [Warning] Changed limits: max_open_files: 1024
(requested 27500)
2017-10-05T12:41:19.198342Z 0 [Warning] Changed limits: max_open_files: 1024
(requested 27500)
As can be seen, mysql tries to increase the open files limit to 27500, but
due to systemd imposed limitation it fails to do so, and then it selects
maximum possible number of connections, based on open files limit.
This was the problem with default setups with pre-systemd installs, but
upstart allowed mysqld to change the limit of open files before mysqld drops
privileges from root to mysql system user.
Even before that, on sysV init, there was a wrapper, mysqld_safe, which run
as root, used ulimit to change the open files limit and then started mysqld as
mysql user.
Would it make sense to ship mysql-server packages with mysql.service unit
files so that there is no limit for open files, or so that open files limit is
substantially higher than 1024?
This was all discussed when Ubuntu 15.10 came out, for mysql-5.6, in
bug LP: #1434758, but I am still bringing this up for more recent
mysql versions.
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