The limitations described in this section relate to functionality in the MySQL Server that is unsupported or reduced, or otherwise differs when using it with MySQL Cluster Manager.
Replication. Replication is currently not directly supported by MySQL Cluster Manager. See Section 5.3, “MySQL Cluster Manager Limitations Relating to MySQL Cluster”, for more information.
Limited mysqld option modifier support.
MySQL Cluster Manager does not recognize the --loose
,
--maximum
, --enable
, and
--disable
prefixes for
mysqld options used as MySQL Cluster Manager configuration
attributes (for a description of these modifiers, see
Program Option Modifiers). For example, the command
set
loose-skip-innodb:mysqld=true mycluster;
fails with
the error No such config variable loose-skip-innodb
for process mysqld.
The --skip
option modifier is supported in some
but not all cases, so that commands such as
set skip-innodb:mysqld=true
mycluster;
and set
skip-grant-tables:mysqld=true mycluster;
can be used
with MySQL Cluster Manager, while set skip-column-names:mysqld=true
mycluster;
cannot. (Bug #48559, Bug #47779)
Visibility of MySQL Cluster Manager mysqld attributes and MySQL
server variables.
Due in part to issues with mappings between
my.cnf
option names,
mysqld command-line option names, and names
of MySQL server variables, some MySQL server variables are not
visible to MySQL Cluster Manager, or have different names. For example, the
storage_engine
server variable
shown in the output of SHOW
VARIABLES
in the mysql client maps
to the default-storage-engine
configuration
attribute used in the MySQL Cluster Manager get
and set
commands.
Dashes and underscores in MySQL option and variable names.
When using the mysql client or other MySQL
client applications, many MySQL system options and variables can
be named using either dashes or underscores in their names. For
example, you can use either ndb_batch_size
or
ndb-batch-size
with the MySQL Server, and the
variable is set correctly. This is not the case in MySQL Cluster Manager, where
only the forms using underscores are accepted as attribute
names. For example, assuming that mycluster
is a viable cluster, the command
set
ndb_batch_size:mysqld=65536 mycluster;
works to set
the size of ndb_batch_size on all mysqld
processes in the cluster, but set
ndb-batch-size:mysqld=65536 mycluster;
fails.
Dependencies between MySQL Cluster Manager mysqld attributes and MySQL server variables. MySQL Cluster Manager does not track dependencies between mysqld attributes (MySQL server options and system variables). That means MySQL Cluster Manager might have mysqld started successfully and report so, even though the server has ended up in a non-functional state because dependent attributes were set inconsistently. It is therefore a good idea for users to check the mysqld attributes before starting the node and the mysql log for status of the node after it has been started.
MySQL Cluster Manager mysqld attributes and MySQL user variables. MySQL user variables are not accessible as MySQL Cluster Manager configuration attributes.
Default MySQL data directory.
Formerly, the default tmpdir
for MySQL servers installed under MySQL Cluster Manager was
datadir
/tmp
,
which caused issues with the mysql client.
This issue was resolved in MySQL Cluster Manager 1.2. MySQL Cluster Manager 1.3 (and later) uses
tmp
in the MySQL installation directory for
this purpose.