This section covers trouble shooting the upgrade process.
MySQL Shell uses the host value of the provided connection
parameters as the target hostname used for AdminAPI
operations, namely to register the instance in the metadata
operations). However, the actual host used for the
connection parameters might not match the
hostname that is used or
reported by Group Replication, which uses the value of the
report_host system variable
when it is defined (in other words it is not
NULL), otherwise the value of
hostname is used.
Therefore, AdminAPI now follows the same logic to register
the target instance in the metadata and as the default value
variable on instances, instead of using the host value from
the instance connection parameters. When the
report_host variable is set
to empty, Group Replication uses an empty value for the host
but AdminAPI (for example in commands such as
dba.createCluster(), and so on) reports
the hostname as the value used which is inconsistent with
the value reported by Group Replication. If an empty value
is set for the
system variable, an error is generated. (Bug #28285389)
For a cluster created using a MySQL Shell version earlier
than 8.0.16, an attempt to reboot the cluster from a
complete outage performed using version 8.0.16 or higher
results in this error. This is caused by a mismatch of the
Metadata values with the
hostname values reported by
the instances. The workaround is to:
Identify which of the instances is the “seed”, in other words the one with the most recent GTID set. The
dba.rebootClusterFromCompleteOutage()operation detects whether the instance is a seed and the operation generates an error if the current session is not connected to the most up-to-date instance.
report_hostsystem variable to the value that is stored in the Metadata schema for the target instance. This value is the
hostname:portpair used in the instance definition upon cluster creation. The value can be consulted by querying the
For example, suppose a cluster was created using the following sequence of commands:
mysql-js> \c clusterAdmin@localhost:3306 mysql-js> dba.createCluster("myCluster")
Therefore the hostname value stored in the metadata is “localhost” and for that reason,
report_hostmust be set to “localhost” on the seed.
Reboot the cluster using only the seed instance. At the interactive prompts do not add the remaining instances to the cluster.
to add the other instances back to the cluster.
Remove the seed instance from the cluster
Stop mysqld on the seed instance and either remove the forced
report_hostsetting (step 2), or replace it with the value previously stored in the Metadata value.
Restart the seed instance and add it back to the cluster using
This allows a smooth and complete upgrade of the cluster to
the latest MySQL Shell version. Another possibility, that
depends on the use-case, is to simply set the value of
report_host on all cluster
members to match what has been registered in the Metadata
schema upon cluster creation.