Merge "Declare plainly the current state of PostgreSQL in OpenStack"

resolutions/20170613-postgresql-status.rst

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+======================================================================
+ 2017-06-13 Document current level of community database support
+======================================================================
+
+Over the years, OpenStack's ecosystem and developer community grew
+around MySQL (as defined in [#f2]_). Emerging from the OpenStack
+User Survey 2017 [#f1]_ there is a trend visible that most production
+deployments today settle on MySQL as the configured database backend.
+
+Although the OpenStack User Survey is non-authoritative, its reported
+bias (> 10 to 1 for MySQL [#f2]_ vs. PostgreSQL [#f3]_) is also
+mirrored in openstack-operator mailing list posts, ask.openstack.org
+posts, and content during operator meetups. In contrast, production
+deployments using PostgreSQL appear to be less popular ([#f4]_).
+
+The OpenStack community is generally offering wide ranges of options
+to the users. For DBMS we advocate the use of abstraction layers
+like for example oslo.db and SQLAlchemy to avoid a lock-in on a
+specific database implementation.
+
+Still the development community could design and develop individual
+features with specific backends in mind. Even if portability issues
+are caught during code review and various levels of automated QA,
+there is still impact on the community like documentation and other
+cost of handling peculiarities of each DBMS like best practices
+for each implementation choice.
+
+Therefore, we should clearly state that currently in the OpenStack
+community there is a bias towards MySQL [#f2]_ over other
+databases like for example PostgreSQL.
+
+As a set of concrete steps we should do the following:
+
+- The OpenStack documentation should be updated to document the
+  community preference::
+
+    .. warning::
+
+       While OpenStack can be used with many SQL DBMS, please
+       be aware that the upstream OpenStack developer community
+       is so far focusing on the MySQL family of databases
+       as a backend and tests OpenStack against the version of
+       MySQL provided with Operating System distributions.
+
+       If you exclusively rely on the OpenStack upstream
+       community and not on an OpenStack vendor for support of your
+       OpenStack installation you are proceeding at your own
+       risk by choosing a different DBMS backend.
+
+- We should state to the OpenStack Foundation that there needs
+  to be a way for distributors to report back aggregate data about
+  their users, who are not self reporting to the survey. The upstream
+  community does not have infinite resources, and is legitimately
+  trying to make hard and informed decisions about things not to do.
+  Because there is no mandatory registration of clouds, the best
+  information we can get is via the User Survey and what vendors
+  decide to share.
+
+In the future we may want to make stronger statements, but the
+important thing is being clear to users that PostgreSQL is currently
+not first class supported upstream and there isn't any
+coordinated effort to change that.
+
+This should not exclude vendors claiming support for other DBMS choices
+for their customers. However, for users bypassing vendors and
+going straight to upstream, the current reality of OpenStack
+enablement needs to be clear.
+
+
+.. rubric:: Footnotes
+
+.. [#f1] April 2017 User Survey
+         https://www.openstack.org/assets/survey/April2017SurveyReport.pdf
+.. [#f2] The term MySQL is used as a reference to the MySQL database and
+         the close variants MariaDB and Galera.
+.. [#f3] The term PostgreSQL is used as a reference to the PostgreSQL
+         database and close derivatives.
+.. [#f4] As of the Boston Forum (May 2017) known users of PostgreSQL
+         are:
+
+         - SUSE: investigating migrating to Galera
+         - Huawei: not actually PostgreSQL, but an internal db based on pg.
+         - Windriver
+         - SAP: consuming OpenStack directly, not via vendor. They
+           did not respond to the user survey, so their usage is not
+           recorded there.