Chapter 5. Upgrading and Downgrading MySQL Cluster

Chapter 5. Upgrading and Downgrading MySQL Cluster
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Chapter 5. Upgrading and Downgrading MySQL Cluster

Table of Contents

5.1. Performing a Rolling Restart of a MySQL Cluster
5.2. MySQL Cluster 5.1 and MySQL Cluster NDB 6.x/7.x Upgrade and Downgrade Compatibility

This portion of the MySQL Cluster chapter covers upgrading and downgrading a MySQL Cluster from one MySQL release to another. It discusses different types of Cluster upgrades and downgrades, and provides a Cluster upgrade/downgrade compatibility matrix (see Section 5.2, “MySQL Cluster 5.1 and MySQL Cluster NDB 6.x/7.x Upgrade and Downgrade Compatibility”). You are expected already to be familiar with installing and configuring a MySQL Cluster prior to attempting an upgrade or downgrade. See Chapter 3, MySQL Cluster Configuration.

For information about upgrading or downgrading between MySQL Cluster NDB releases, or between MySQL Cluster NDB releases and mainline MySQL releases, see the changelogs relating to MySQL Cluster NDB.

This section remains in development, and continues to be updated and expanded.

5.1. Performing a Rolling Restart of a MySQL Cluster

This section discusses how to perform a rolling restart of a MySQL Cluster installation, so called because it involves stopping and starting (or restarting) each node in turn, so that the cluster itself remains operational. This is often done as part of a rolling upgrade or rolling downgrade, where high availability of the cluster is mandatory and no downtime of the cluster as a whole is permissible. Where we refer to upgrades, the information provided here also generally applies to downgrades as well.

There are a number of reasons why a rolling restart might be desirable:

Cluster configuration change. To make a change in the cluster's configuration, such as adding an SQL node to the cluster, or setting a configuration parameter to a new value.
Cluster software upgrade/downgrade. To upgrade the cluster to a newer version of the MySQL Cluster software (or to downgrade it to an older version). This is usually referred to as a “rolling upgrade” (or “rolling downgrade”, when reverting to an older version of MySQL Cluster).
Change on node host. To make changes in the hardware or operating system on which one or more cluster nodes are running
Cluster reset. To reset the cluster because it has reached an undesirable state
Freeing of resources. To allow memory allocated to a table by successive INSERT and DELETE operations to be freed for re-use by other Cluster tables

The process for performing a rolling restart may be generalised as follows:

Stop all cluster management nodes (ndb_mgmd processes), reconfigure them, then restart them
Stop, reconfigure, then restart each cluster data node (ndbd process) in turn
Stop, reconfigure, then restart each cluster SQL node (mysqld process) in turn

The specifics for implementing a particular rolling upgrade depend upon the actual changes being made. A more detailed view of the process is presented here:

MySQL Cluster Rolling Restarts (By
Type)

In the previous diagram, Stop and Start steps indicate that the process must be stopped completely using a shell command (such as kill on most Unix systems) or the management client STOP command, then started again from a system shell by invoking the ndbd or ndb_mgmd executable as appropriate. Restart indicates the process may be restarted using the ndb_mgm management client RESTART command.

Important

When performing an upgrade or downgrade of the cluster software, you must upgrade or downgrade the management nodes first, then the data nodes, and finally the SQL nodes. Doing so in any other order may leave the cluster in an unusable state.

5.2. MySQL Cluster 5.1 and MySQL Cluster NDB 6.x/7.x Upgrade and Downgrade Compatibility

This section provides information about MySQL Cluster software and table file compatibility between MySQL 5.1 and MySQL Cluster NDB 6.x releases with regard to performing upgrades and downgrades.

Important

Only compatibility between MySQL versions with regard to NDBCLUSTER is taken into account in this section, and there are likely other issues to be considered. As with any other MySQL software upgrade or downgrade, you are strongly encouraged to review the relevant portions of the MySQL Manual for the MySQL versions from which and to which you intend to migrate, before attempting an upgrade or downgrade of the MySQL Cluster software. See Upgrading MySQL.

The following table shows Cluster upgrade and downgrade compatibility between different releases of MySQL 5.1:

MySQL Cluster upgrade/downgrade compatibility,
MySQL 5.1

Notes — MySQL 5.1.

MySQL 5.1.3 was the first public release in this series.
Direct upgrades or downgrades between MySQL Cluster 5.0 and 5.1 are not supported; you must dump all NDBCLUSTER tables using mysqldump, install the new version of the software, and then reload the tables from the dump.
You cannot downgrade a MySQL 5.1.6 or later Cluster using Disk Data tables to MySQL 5.1.5 or earlier unless you convert all such tables to in-memory Cluster tables first.
MySQL 5.1.8, MySQL 5.1.10, and MySQL 5.1.13 were not released.
Online cluster upgrades and downgrades between MySQL 5.1.11 (or an earlier version) and 5.1.12 (or a later version) are not possible due to major changes in the cluster file system. In such cases, you must perform a backup or dump, upgrade (or downgrade) the software, start each data node with --initial, and then restore from the backup or dump. You can use NDB backup/restore or mysqldump for this purpose.
Online downgrades from MySQL 5.1.14 or later to versions previous to 5.1.14 are not supported due to incompatible changes in the cluster system tables.
Online upgrades from MySQL 5.1.17 and earlier to 5.1.18 and later are not supported for clusters using replication due to incompatible changes in the mysql.ndb_apply_status table. However, it should not be necessary to shut down the cluster entirely, if you follow this modified rolling restart procedure:
1. Stop the management server, update the ndb_mgmd binary, then start it again. For multiple management servers, repeat this step for each management server in turn.
2. For each data node in turn: Stop the data node, replace the ndbd binary with the new version, then restart the data node. It is not necessary to use --initial when restarting any of the data nodes.
3. Stop all SQL nodes. Replace the mysqld binary with the new version for all SQL nodes, then restart them. It is not necessary to start them one at a time, but they must all be shut down at the same time before starting any of them again using the 5.1.18 (or later) mysqld. Otherwise — due to the fact that mysql.ndb_apply_status uses the NDB storage engine and is thus shared between all SQL nodes — there may be conflicts between MySQL servers using the old and new versions of the table.
You can find more information about the changes to ndb_apply_status in Section 9.4, “MySQL Cluster Replication Schema and Tables”.
The internal specifications for columns in NDBCLUSTER tables changed in MySQL 5.1.18 to allow compatibility with later MySQL Cluster releases that allow online adding and dropping of columns. This change is not backward-compatible with earlier MySQL versions.
In order to make tables created in MySQL 5.1.17 and earlier compatible with online adding and dropping of columns (available beginning with beginning with MySQL Cluster NDB 6.2.5 and MySQL Cluster NDB 6.3.3 — see ALTER TABLE Syntax, for more information), it is necessary to force MySQL 5.1.18 and later to convert the tables to the new format by following this procedure:
1. Back up all NDBCLUSTER tables.
2. Upgrade the MySQL Cluster software on all data, management, and SQL nodes.
3. Shut down the cluster completely (this includes all data, management, and API or SQL nodes).
4. Restart the cluster, starting all data nodes with the --initial option (to clear and rebuild the data node file systems).
5. Restore the NDBCLUSTER tables from backup.
This is not necessary for NDBCLUSTER tables created in MySQL 5.1.18 and later; such tables will automatically be compatible with online adding and dropping of columns (as implemented beginning with MySQL Cluster NDB 6.2.5 and MySQL Cluster NDB 6.3.2).
In order to minimise possible later difficulties, it is strongly advised that the procedure outlined above be followed as soon as possible after to upgrading from MySQL 5.1.17 or earlier to MySQL 5.1.18 or later.
Information about how this change effects users of MySQL Cluster NDB 6.x/7.0 is provided later in this section.
MySQL Cluster is not supported in standard MySQL 5.1 releases, beginning with MySQL 5.1.25. If you are using MySQL Cluster in a standard MySQL 5.1 release, you should upgrade to the most recent MySQL Cluster NDB 6.2 or 6.3 release.

The following table shows Cluster upgrade and downgrade compatibility between different releases of MySQL Cluster NDB 6.x/7.0:

MySQL Cluster upgrade/downgrade compatibility,
MySQL Cluster NDB 6.x/7.0

Notes — MySQL Cluster NDB 6.x/7.x.

MySQL Cluster NDB 6.1 is no longer in production; if you are still using a MySQL Cluster NDB 6.1 release, you should upgrade to the most recent MySQL Cluster NDB 6.2 or 6.3 as soon as possible.
It is not possible to upgrade from MySQL Cluster NDB 6.1.2 (or an older 6.1 release) directly to 6.1.4 or a newer NDB 6.1 release, or to downgrade from 6.1.4 (or a newer 6.1 release) directly to 6.1.2 or an older NDB 6.1 release; in either case, you must upgrade or downgrade to MySQL Cluster NDB 6.1.3 first.
It is not possible to perform an online downgrade from MySQL Cluster NDB 6.1.8 (or a newer 6.1 release) to MySQL Cluster NDB 6.1.7 (or an older 6.1 release).
MySQL Cluster NDB 6.1.6 and 6.1.18 were not released.
It is not possible to perform an online upgrade or downgrade between MySQL Cluster NDB 6.2 and any previous release series (including mainline MySQL 5.1 and MySQL Cluster NDB 6.1); it is necessary to perform a dump and reload. However, it should be possible to perform online upgrades or downgrades between any MySQL Cluster NDB 6.2 release and any MySQL Cluster NDB 6.3 release up to and including 6.3.7.
The internal specifications for columns in NDB tables changed in MySQL Cluster NDB 6.1.17 and 6.2.1 to allow compatibility with future MySQL Cluster releases that are expected to implement online adding and dropping of columns. This change is not backward-compatible with earlier MySQL or MySQL Cluster NDB 6.x versions.
In order to make tables created in earlier versions compatible with online adding and dropping of columns in later versions, it is necessary to force MySQL Cluster to convert the tables to the new format by following this procedure following an upgrade:
1. Upgrade the MySQL Cluster software on all data, management, and SQL nodes
2. Back up all NDB tables
3. Shut down the cluster (all data, management, and SQL nodes)
4. Restart the cluster, starting all data nodes with the --initial option (to clear and rebuild the data node file systems)
5. Restore the tables from backup
In order to minimise possible later difficulties, it is strongly advised that the procedure outlined above be followed as soon as possible after to upgrading between the versions indicated. The procedure is not necessary for NDBCLUSTER tables created in any of the following versions:
- MySQL Cluster NDB 6.1.8 or a later MySQL Cluster NDB 6.1 release
- MySQL Cluster 6.2.1 or a later MySQL Cluster NDB 6.2 release
- Any MySQL Cluster NDB 6.3 release
Tables created in the listed versions (or later ones, as indicated) are already compatible with online adding and dropping of columns (as implemented beginning with MySQL Cluster NDB 6.2.5 and MySQL Cluster NDB 6.3.2).
It was not possible to perform an online upgrade between any MySQL Cluster NDB 6.2 release and MySQL Cluster NDB 6.3.8 and later MySQL Cluster 6.3 releases. This issue was fixed in MySQL Cluster NDB 6.3.21. (Bug#41435)
Online downgrades between MySQL Cluster NDB 6.2.5 and earlier releases are not supported.
Online downgrades between MySQL Cluster NDB 6.3.8 and earlier releases are not supported.
Online upgrades from any MySQL Cluster NDB 7.0 release up to and including MySQL Cluster NDB 7.0.4 (as well as all early releases numbered NDB 6.4.x) to MySQL Cluster NDB 7.0.5 or later are not possible. Upgrades to MySQL Cluster NDB 7.0.6 or later from MySQL Cluster NDB 6.3.8 or a later MySQL Cluster NDB 6.3 release, or from MySQL Cluster NDB 7.0.5 or later, are supported. (Bug#44294)