Merge "Percona-cluster to mysql-innodb-cluster migration"
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Zuul
Gerrit Code Review
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@ -306,6 +306,11 @@ Stateful Services
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Procedure for the stateful services deployed on LXD containers.
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These include percona-cluster and rabbitmq.
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.. warning::
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For Bionic to Focal series upgrades see percona-cluster migration to
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mysql-innodb-cluster and mysql-router under Series Specific Procedures.
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.. note::
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While percona-cluster is often deployed with hacluster for HA,
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@ -491,3 +496,173 @@ Juju set-series to the new series for all future units of an application.
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<!-- LINKS -->
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.. _Charm upgrades: app-upgrade-openstack#charm-upgrades
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Series Specific Procedures
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++++++++++++++++++++++++++
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Bionic to Focal
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~~~~~~~~~~~~~~~
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percona-cluster migration to mysql-innodb-cluster and mysql-router
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__________________________________________________________________
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In Ubuntu 20.04 LTS (Focal) the percona-xtradb-cluster-server package will no
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longer be available. It has been replaced by mysql-server-8.0 and mysql-router
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in Ubuntu main. Therefore, there is no way to series upgrade percona-cluster to
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Focal. Instead the databases hosted by percona-cluster will need to be migrated
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to mysql-innodb-cluster and mysql-router will need to be deployed as a
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subordinate on the applications that use MySQL as a data store.
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.. warning::
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Since the DB affects most OpenStack services it is important to have a
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sufficient downtime window. The following procedure is written in an attempt
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to migrate one service at a time (i.e. keystone, glance, cinder, etc).
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However, it may be more practical to migrate all databases at the same time
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during an extended downtime window, as there may be unexpected
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interdependencies between services.
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.. note::
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It is possible for percona-cluster to remain on Ubuntu 18.04 LTS while
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the rest of the cloud migrates to Ubuntu 20.04 LTS. In fact, this state
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will be one step of the migration process.
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Procedure
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* Leave all the percona-cluster machines on Bionic and upgrade the series of
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the remaining machines in the cloud per this document.
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* Deploy a mysql-innodb-cluster on Focal.
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.. code-block:: none
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juju deploy -n 3 mysql-innodb-cluster --series focal
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* Deploy (but do not yet relate) an instance of mysql-router for every
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application that requires a data store (i.e. every application that was
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related to percona-cluster).
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.. code-block:: none
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juju deploy mysql-router cinder-mysql-router
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juju deploy mysql-router glance-mysql-router
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juju deploy mysql-router keystone-mysql-router
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...
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* Add relations between the mysql-router instances and the
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mysql-innodb-cluster.
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.. code-block:: none
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juju add-relation cinder-mysql-router:db-router mysql-innodb-cluster:db-router
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juju add-relation glance-mysql-router:db-router mysql-innodb-cluster:db-router
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juju add-relation keystone-mysql-router:db-router mysql-innodb-cluster:db-router
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...
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On a per-application basis:
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* Remove the relation between the application charm and the percona-cluster
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charm. You can view existing relations with the :command:`juju status
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percona-cluster --relations` command.
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.. code-block:: none
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juju remove-relation keystone:shared-db percona-cluster:shared-db
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* Dump the existing database(s) from percona-cluster.
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.. note::
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In the following, the percona-cluster/0 and mysql-innodb-cluster/0 units
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are used as examples. For percona, any unit of the application may be used,
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though all the steps should use the same unit. For mysql-innodb-cluster,
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the RW unit should be used. The RW unit of the mysql-innodb-cluster can be
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determined from the :command:`juju status mysql-innodb-cluster` command.
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* Allow Percona to dump databases. See `Percona strict mode`_ to understand
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the implications of this setting.
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.. code-block:: none
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juju run-action --wait percona-cluster/0 set-pxc-strict-mode mode=MASTER
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* Dump the specific application's database(s).
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.. note::
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Depending on downtime restrictions it is possible to dump all databases at
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one time: run the ``mysqldump`` action without setting the ``databases``
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parameter. Similarly, it is possible to import all the databases into
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mysql-innodb-clulster from that single dump file.
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.. note::
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The database name may or may not match the application name. For example,
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while keystone has a DB named keystone, openstack-dashboard has a database
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named horizon. Some applications have multiple databases. Notably,
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nova-cloud-controller which has at least: nova,nova_api,nova_cell0 and a
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nova_cellN for each additional cell. See upstream documentation for the
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respective application to determine the database name.
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.. code-block:: none
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# Single DB
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juju run-action --wait percona-cluster/0 mysqldump databases=keystone
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# Multiple DBs
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juju run-action --wait percona-cluster/0 mysqldump databases=nova,nova_api,nova_cell0
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* Return Percona enforcing strict mode. See `Percona strict mode`_ to
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understand the implications of this setting.
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.. code-block:: none
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juju run-action --wait percona-cluster/0 set-pxc-strict-mode mode=ENFORCING
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* Transfer the mysqldump file from the percona-cluster unit to the
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mysql-innodb-cluster RW unit. The RW unit of the mysql-innodb-cluster can be
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determined from juju status: `juju status mysql-innodb-cluster`. Bellow we
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use mysql-innodb-cluster/0 as an example.
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.. code-block:: none
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juju scp percona-cluster/0:/var/backups/mysql/mysqldump-keystone-<DATE>.gz .
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juju scp mysqldump-keystone-<DATE>.gz mysql-innodb-cluster/0:/home/ubuntu
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* Import the database(s) into mysql-innodb-cluster.
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.. code-block:: none
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juju run-action --wait mysql-innodb-cluster/0 restore-mysqldump dump-file=/home/ubuntu/mysqldump-keystone-<DATE>.gz
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* Relate an instance of mysql-router for every application that requires a data
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store (i.e. every application that needed percona-cluster):
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.. code-block:: none
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juju add-relation keystone:shared-db keystone-mysql-router:shared-db
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* Repeat for remaining applications.
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An overview of this process can be seen in the OpenStack charmer's team CI `Zaza migration code`_.
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Post-migration
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As noted above it is possible to run the cloud with percona-cluster remaining
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on Bionic indefinitely. Once all databases have been migrated to
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mysql-innodb-cluster, all the databases have been backed up, and the cloud has
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been verified to be in good working order the percona-cluster application (and
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its probable hacluster subordinates) may be removed.
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.. code-block:: none
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juju remove-application percona-cluster-hacluster
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juju remove-application percona-cluster
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.. _Zaza migration code: https://github.com/openstack-charmers/zaza-openstack-tests/blob/master/zaza/openstack/charm_tests/mysql/tests.py#L556
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.. _Percona strict mode: https://www.percona.com/doc/percona-xtradb-cluster/LATEST/features/pxc-strict-mode.html
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