MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6
Multiple SQL nodes.
The following are issues relating to the use of multiple MySQL
servers as NDB Cluster SQL nodes, and are specific to the
NDBCLUSTER storage engine:
Stored programs not distributed.
Stored procedures, stored functions, triggers, and
scheduled events are all supported by tables using the
NDB storage engine, but these
do not propagate automatically
between MySQL Servers acting as Cluster SQL nodes, and
must be re-created separately on each SQL node. See
Stored Programs in NDB Cluster.
No distributed table locks.
A LOCK TABLES statement or
GET_LOCK() call works only
for the SQL node on which the lock is issued; no other SQL
node in the cluster “sees” this lock. This is
true for a lock issued by any statement that locks tables
as part of its operations. (See next item for an example.)
Implementing table locks in NDBCLUSTER
can be done in an API application, and ensuring that all
applications start by setting
LockMode to
LM_Read or
LM_Exclusive. For more information about
how to do this, see the description of
NdbOperation::getLockHandle()
in the NDB Cluster API Guide.
ALTER TABLE operations.
ALTER TABLE is not fully
locking when running multiple MySQL servers (SQL nodes).
(As discussed in the previous item, NDB Cluster does not
support distributed table locks.)
Multiple management nodes. When using multiple management servers:
If any of the management servers are running on the same host, you must give nodes explicit IDs in connection strings because automatic allocation of node IDs does not work across multiple management servers on the same host. This is not required if every management server resides on a different host.
When a management server starts, it first checks for any
other management server in the same NDB Cluster, and upon
successful connection to the other management server uses
its configuration data. This means that the management
server --reload and
--initial startup options
are ignored unless the management server is the only one
running. It also means that, when performing a rolling
restart of an NDB Cluster with multiple management nodes,
the management server reads its own configuration file if
(and only if) it is the only management server running in
this NDB Cluster. See
Section 21.6.5, “Performing a Rolling Restart of an NDB Cluster”, for more
information.
Multiple network addresses. Multiple network addresses per data node are not supported. Use of these is liable to cause problems: In the event of a data node failure, an SQL node waits for confirmation that the data node went down but never receives it because another route to that data node remains open. This can effectively make the cluster inoperable.
It is possible to use multiple network hardware
interfaces (such as Ethernet cards) for a
single data node, but these must be bound to the same address.
This also means that it not possible to use more than one
[tcp] section per connection in the
config.ini file. See
Section 21.4.3.10, “NDB Cluster TCP/IP Connections”, for more
information.