7.2 InnoDB Cluster 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 Group Replication Limitations.

• Important

  Due to an error in a metadata query, MySQL Shell 8.0.27 cannot be used to manage an InnoDB Cluster running MySQL Server 8.0.25. To work around this issue, upgrade MySQL Server to the 8.0.26 or 8.0.27 release on the InnoDB Cluster member instances before using MySQL Shell 8.0.27 with the cluster. The issue will be fixed in MySQL Shell 8.0.28.

• InnoDB Cluster does not manage manually configured asynchronous replication channels. Group Replication and AdminAPI do not ensure that the asynchronous replication is active on the primary only, and state is not replicated across instances. This can lead to various scenarios where replication no longer works, as well as potentially causing a split brain. Replication between one InnoDB Cluster and another is supported only by InnoDB ClusterSet, which is available from MySQL 8.0.27 and manages replication from an active primary read-write InnoDB Cluster to multiple read-only replica clusters. For information on that solution, see Chapter 8, MySQL InnoDB ClusterSet.

• InnoDB Cluster is intended to be deployed in a local area network. Deploying a single InnoDB Cluster over a wide area network has a noticeable impact on write performance. A stable and low latency network is important for InnoDB Cluster member servers to communicate with each other using the underlying Group Replication technology for consensus on transactions. InnoDB ClusterSet, however, is designed to be deployed across multiple datacenters, with each InnoDB Cluster in a single datacenter and asynchronous replication channels linking them. For information on that solution, see Chapter 8, MySQL InnoDB ClusterSet.

• For AdminAPI operations, you can only connect to server instances in an InnoDB Cluster using TCP/IP connections and classic MySQL protocol. The use of Unix sockets and named pipes is not supported for AdminAPI operations, and the use of X Protocol is not supported for AdminAPI operations. The same limitations apply to connections between the server instances themselves.

  Note

  Client applications can use X Protocol and Unix sockets and named pipes to connect to instances in an InnoDB Cluster. The limitations only apply to administration operations using AdminAPI commands, and to connections between the instances.

• AdminAPI and InnoDB Cluster support the use of instances running MySQL Server 5.7. However, there are additional limitations for these instances, and some of the features described do not apply when you use them. Section 6.2.1, “Using Instances Running MySQL 5.7” lists the additional limitations.

• Concurrent data definition statements and data manipulation statements issued against the same object but on different servers is not supported when using multi-primary mode. During the issue of Data Definition Language (DDL) statements on an object, issuing concurrent Data Manipulation Language (DML) on the same object but from a different server instance has the risk of conflicting DDL executing on different instances not being detected. For more information, see Group Replication Limitations.