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MySQL 8.0 Reference Manual  /  InnoDB Cluster  /  Known Limitations

Pre-General Availability Draft: 2018-02-24

22.5 Known Limitations

This section describes the known limitations of InnoDB cluster. As InnoDB cluster uses Group Replication, you should also be aware of its limitations, see Section 21.7.2, “Group Replication Limitations”.

  • The formatting of results which contain multi-byte characters sometimes do not have correctly aligned columns. Similarly, non-standard character sets are being corrupted in results.

  • AdminAPI does not support Unix socket connections. MySQL Shell currently does not prevent you from attempting to use socket connections to a cluster, and attempting to use a socket connection to a cluster can cause unexpected results.

  • The MySQL Shell help describes an invalid URI:

    USER[:PASS]@::SOCKET[/DB].

    This is invalid because the @ symbol can not be present if no user information is provided.

  • If a session type is not specified when creating the global session, MySQL Shell provides automatic protocol detection which attempts to first create a NodeSession and if that fails it tries to create a ClassicSession. With an InnoDB cluster that consists of three server instances, where there is one read-write port and two read-only ports, this can cause MySQL Shell to only connect to one of the read-only instances. Therefore it is recommended to always specify the session type when creating the global session.

  • When adding non-sandbox server instances (instances which you have configured manually rather than using dba.deploySandboxInstance() ) to a cluster, MySQL Shell is not able to persist any configuration changes in the instance's configuration file. This leads to one or both of the following scenarios:

    1. The Group Replication configuration is not persisted in the instance's configuration file and upon restart the instance does not rejoin the cluster.

    2. The instance is not valid for cluster usage. Although the instance can be verified with dba.checkInstanceConfiguration(), and MySQL Shell makes the required configuration changes in order to make the instance ready for cluster usage, those changes are not persisted in the configuration file and so are lost once a restart happens.

    If only a happens, the instance does not rejoin the cluster after a restart.

    If b also happens, and you observe that the instance did not rejoin the cluster after a restart, you cannot use the recommended dba.rebootClusterFromCompleteOutage() in this situation to get the cluster back online. This is because the instance loses any configuration changes made by MySQL Shell, and because they were not persisted, the instance reverts to the previous state before being configured for the cluster. This causes Group Replication to stop responding, and eventually the command times out.

    To avoid this problem it is strongly recommended to use dba.configureLocalInstance() before adding instances to a cluster in order to persist the configuration changes.

  • The use of the --defaults-extra-file option to specify an option file is not supported by InnoDB cluster server instances.

  • An instance with MySQL version 8.0.4 could hang indefinitely in the event of a failed attempt to join a cluster caused by all group seeds (group_replication_group_seeds) being unreachable. Such an event can happen after a cluster complete outage, in other words where all instances of the cluster crash and are afterwards restarted.


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