openstack/cinder-specs
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cinder-specs/specs/liberty/db2-database.rst
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Change-Id: Iafd7f7b95d5a17fca243319f1cfae81012b29ed0
2016-05-13 10:26:22 -06:00

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Add Cinder Support for DB2 (v10.5+)

Include the URL of your launchpad blueprint:

https://blueprints.launchpad.net/cinder/+spec/db2-database

The community currently supports MySQL and PostgreSQL production databases. Several other core projects already support DB2 (Keystone, Glance, Ceilometer, Heat). This blueprint adds support to Cinder for DB2 as a production database.

Problem description

  • Currently there is no support in the community for a deployer to run Cinder against a DB2 backend database.
  • For anyone running applications against an existing DB2 database that wants to move to OpenStack, they'd have to use a different database engine to run Cinder in OpenStack.
  • There is currently an inconsistent support matrix across the core projects since the majority of core projects support DB2 but Cinder does not yet.

Use Cases

Proposed change

The changes required to enable Cinder to run on DB2 are limited given that Cinder's database structure is not complicated. No changes are currently required to the migration scripts to enable deployment on a DB2 database.

Unit test will need to be updated to support running tests against a DB2 backend with the ibm_db_sa driver and all Cinder patches will be tested against a Tempest full run with 3rd party CI running DB2, maintained by IBM. Note that these 3rd Party CI runs have already been enabled for Cinder.

There is already code in Oslo's db.api layer to support common function with DB2 like duplicate entry error handling and connection trace, so that is not part of this spec. Cinder, however, will need to sync up to the latest Oslo DB code to enable DB2 support.

Alternatives

Deployers can use other supported database backends like MySQL or PostgreSQL, but this may not be an ideal option for customers already running applications with DB2 that want to integrate with OpenStack. In addition, you could run other core projects with multiple schemas in a single DB2 OpenStack database, but you'd have to run Cinder separately which is a maintenance/configuration problem.

Data model impact

There are no impacts on the current Cinder data model. Any issues that arise due to future changes will be uncovered by the 3rd Party CI tests and will be able to be addressed at that point in time.

The one exception to this statement is in the unit test path. I made two commits in Icehouse to start implementing the infrastructure to enable DB2 unit testing. The commits were to add a bool_type dictionary (2a7b11922bd9389287915c45de92ca5eed3d448e) and a time_type dictionary (a9527de9ed3a2eae951564c3c74b7319113e8bf5). I will need to add the appropriate types for DB2, as was done for MySQL, as part of the unit test changes I will be making for DB2.

REST API impact

None.

Security impact

None.

Notifications impact

None.

Other end user impact

None.

Performance Impact

Execution of migration unit tests on DB2 may take longer than on other backend databases due to the time required to create the database schema. This impact, however, will only be seen when running unit tests for DB2.

Other deployer impact

There are no plans to migrate the Cinder database from a pre-existing installation (I.E. MySQL) to DB2. So deployers will need to be starting with a fresh Cinder installation to enable DB2 as a backend database.

Developer impact

The only impact on developers is if they are adding DB API code or migrations that don't work with DB2, they will have to adjust those appropriately, just like we do today with MySQL and PostgreSQL. IBM ATCs would provide support/guidance on issues like this which require specific conditions for DB2, although for the most part, the DB2 InfoCenter provides adequate detail on how to work with the engine and provides details on error codes.

Implementation

Assignee(s)

Primary assignee:

Email: jsbryant@us.ibm.com Launchpad ID: jsbryant

Work Items

  1. Make the test_migrations.py module work with a configured DB2 backend for running unit tests.
    1. Add the appropriate column types for DB2.
    2. Add support for creating the DB2 schema for Cinder testing.

Dependencies

  • DB2 support was added to sqlalchemy-migrate 0.9 during Icehouse: https://blueprints.launchpad.net/sqlalchemy-migrate/+spec/add-db2-support
  • There are no requirements changes in Cinder for the unit tests to work. The runtime requirements are the ibm-db-sa and ibm_db modules, which are both available from pypi. sqlalchemy-migrate optionally imports ibm-db-sa. The ibm-db-sa module requires a natively compiled ibm_db which has the c binding that talks to the DB2 ODBC/CLI driver.
  • Note that only DB2 10.5+ is supported since that's what added unique index support over nullable columns which is how sqlalchemy-migrate handles unique constraints over nullable columns.

Testing

  • IBM is already running 3rd party CI for DB2 on Cinder.
  • DB2 Unit Test for Cinder will be enabled.

Documentation Impact

References