Quoting MDEV reporter Daniel Lewart:
Starting MariaDB with default configuration causes the following problems:
"[Warning] Could not increase number of max_open_files to more than 16384 (request: 32186)"
silently reduces table_open_cache_instances from 8 (default) to 4
Default Server System Variables:
extra_max_connections = 1
max_connections = 151
table_open_cache = 2000
table_open_cache_instances = 8
thread_pool_size = 4
LimitNOFILE=16834 is in the following files:
support-files/mariadb.service.in
support-files/mariadb@.service.in
Looking at sql/mysqld.cc lines 3837-3917:
wanted_files= (extra_files + max_connections + extra_max_connections +
tc_size * 2 * tc_instances);
wanted_files+= threadpool_size;
Plugging in the default values:
wanted_files = (30 + 151 + 1 + 2000 * 2 * 8 + 4) = 32186
However, systemd configuration has LimitNOFILE = 16384, which is far smaller.
I suggest increasing LimitNOFILE to 32768.
we need to stop server instance on upgrade, but it may be started either by SysV init script or by SystemD.
this commit adds `mysql` target to `systemctl stop` call.
`mysql` may be the name of initscript or an alias while `mariadb` is
a systemd unit file.
Systemd has a socket activation feature where a mariadb.socket
definition defines the sockets to listen to, and passes those
file descriptors directly to mariadbd to use when a connection
occurs.
The new functionality is utilized when starting as follows:
systemctl start mariadb.socket
The mariadb.socket definition only needs to contain the network
information, ListenStream= directives, the mariadb.service
definition is still used for service instigation.
When mariadbd is started in this way, the socket, port, bind-address
backlog are all assumed to be self contained in the mariadb.socket
definition and as such the mariadb settings and command line
arguments of these network settings are ignored.
See man systemd.socket for how to limit this to specific ports.
Extra ports, those specified with extra_port in socket activation
mode, are those with a FileDescriptorName=extra. These need
to be in a separate service name like mariadb-extra.socket and
these require a Service={mariadb.service} directive to map to the
original service. Extra ports need systemd v227 or greater
(not RHEL/Centos7 - v219) when FileDescriptorName= was added,
otherwise the extra ports are treated like ordinary ports.
The number of sockets isn't limited when using systemd socket activation
(except by operating system limits on file descriptors and a minimal
amount of memory used per file descriptor). The systemd sockets passed
can include any ownership or permissions, including those the
mariadbd process wouldn't normally have the permission to create.
This implementation is compatible with mariadb.service definitions.
Those services started with:
systemctl start mariadb.service
does actually start the mariadb.service and used all the my.cnf
settings of sockets and ports like it previously did.
Under WITHOUT_WSREP:
Exclude support files that are server only like
* wsrep.cnf
* wsrep_notify
* log rotate config files
* mysqld_multi
Exclude man pages of server components
liburing is a new optional dependency (WITH_URING=auto|yes|no)
that replaces libaio when it is available.
aio_uring: class which wraps io_uring stuff
aio_uring::bind()/unbind(): optional optimization
aio_uring::submit_io(): mutex prevents data race. liburing calls are
thread-unsafe. But if you look into it's implementation you'll see
atomic operations. They're used for synchronization between kernel and
user-space only. That's why our own synchronization is still needed.
For systemd, we add LimitMEMLOCK=524288 (ulimit -l 524288)
because the io_uring_setup system call that is invoked
by io_uring_queue_init() requests locked memory. The value
was found empirically; with 262144, we would occasionally
fail to enable io_uring when using the maximum values of
innodb_read_io_threads=64 and innodb_write_io_threads=64.
aio_uring::thread_routine(): Tolerate -EINTR return from
io_uring_wait_cqe(), because it may occur on shutdown
on Ubuntu 20.10 (Groovy Gorilla).
This was mostly implemented by Eugene Kosov. Systemd integration
and improved startup/shutdown error handling by Marko Mäkelä.
This is just to make sure no ExecStartPre/Post actions from the
multi-instance MariaDB service definition are executed
when a user attempts to start mariadb@bootstrap.
Fixes: 3723c70a30
