[openstack-dev] [trove][all][tc] A proposal to rearchitect Trove

Amrith Kumar amrith.kumar at gmail.com
Thu Jun 29 14:41:03 UTC 2017


It would be great if these teams were brought into this conversation. I am
not averse to the evolutionary approach, merely observing that in the
absence of commitment and contributors who wish to participate in this
evolution, we will be unable to sustain the project.

Regarding your view that it is feasible and rational to evolve Trove, I
would to understand the rationale behind those judgements and the resources
that you believe that it will take to make those possible, and a clear
statement of what your/IBM's commitment of resources to the project would



On Thu, Jun 29, 2017 at 9:33 AM, Manoj Kumar <kumarmn at us.ibm.com> wrote:

> Amrith: Some comments regarding the scarcity of deployments, and the
> proposed approach.
> We know of multiple teams that are now independently charging down and
> investing in a Trove path.  They are at various stages of deployment and
> are beyond tire-kicking. They are beginning to build dev/test environments,
> some are building commercial products, and we fully expect some people to
> be in production with Trove by the end of the year.  Collectively, we need
> to start bridging and engaging these people into the Trove community.
> We also strongly believe that we need an evolutionary approach to moving
> Trove forward vs. the revolutionary approach that is being proposed.  Our
> deeply held view is that it is feasible and rationale to evolve Trove as it
> exists today.  We agree that there are architectural issues that have to be
> addressed.   Let's start working on addressing these issues as well as the
> current currency issues but in a evolutionary way.  The revolutionary
> approach will halt all progress and set a bad precedent, and we believe
> that it will cause people to walk away from the community and likely
> OpenStack as well.
> - Manoj
> From:        Amrith Kumar <amrith.kumar at gmail.com>
> To:        "OpenStack Development Mailing List (not for usage questions)"
> <openstack-dev at lists.openstack.org>
> Date:        06/18/2017 06:41 AM
> Subject:        [openstack-dev] [trove][all][tc] A proposal to
> rearchitect Trove
> ------------------------------
> Trove has evolved rapidly over the past several years, since integration
> in IceHouse when it only supported single instances of a few databases.
> Today it supports a dozen databases including clusters and replication.
> The user survey [1] indicates that while there is strong interest in the
> project, there are few large production deployments that are known of (by
> the development team).
> Recent changes in the OpenStack community at large (company realignments,
> acquisitions, layoffs) and the Trove community in particular, coupled with
> a mounting burden of technical debt have prompted me to make this proposal
> to re-architect Trove.
> This email summarizes several of the issues that face the project, both
> structurally and architecturally. This email does not claim to include a
> detailed specification for what the new Trove would look like, merely the
> recommendation that the community should come together and develop one so
> that the project can be sustainable and useful to those who wish to use it
> in the future.
> Trove, with support for a dozen or so databases today, finds itself in a
> bind because there are few developers, and a code-base with a significant
> amount of technical debt.
> Some architectural choices which the team made over the years have
> consequences which make the project less than ideal for deployers.
> Given that there are no major production deployments of Trove at present,
> this provides us an opportunity to reset the project, learn from our v1 and
> come up with a strong v2.
> An important aspect of making this proposal work is that we seek to
> eliminate the effort (planning, and coding) involved in migrating existing
> Trove v1 deployments to the proposed Trove v2. Effectively, with work
> beginning on Trove v2 as proposed here, Trove v1 as released with Pike will
> be marked as deprecated and users will have to migrate to Trove v2 when it
> becomes available.
> While I would very much like to continue to support the users on Trove v1
> through this transition, the simple fact is that absent community
> participation this will be impossible. Furthermore, given that there are no
> production deployments of Trove at this time, it seems pointless to build
> that upgrade path from Trove v1 to Trove v2; it would be the proverbial
> bridge from nowhere.
> This (previous) statement is, I realize, contentious. There are those who
> have told me that an upgrade path must be provided, and there are those who
> have told me of unnamed deployments of Trove that would suffer. To this,
> all I can say is that if an upgrade path is of value to you, then please
> commit the development resources to participate in the community to make
> that possible. But equally, preventing a v2 of Trove or delaying it will
> only make the v1 that we have today less valuable.
> We have learned a lot from v1, and the hope is that we can address that in
> v2. Some of the more significant things that I have learned are:
> - We should adopt a versioned front-end API from the very beginning;
> making the REST API versioned is not a ‘v2 feature’
> - A guest agent running on a tenant instance, with connectivity to a
> shared management message bus is a security loophole; encrypting traffic,
> per-tenant-passwords, and any other scheme is merely lipstick on a security
> hole
> - Reliance on Nova for compute resources is fine, but dependence on Nova
> VM specific capabilities (like instance rebuild) is not; it makes things
> like containers or bare-metal second class citizens
> - A fair portion of what Trove does is resource orchestration; don’t
> reinvent the wheel, there’s Heat for that. Admittedly, Heat wasn’t as far
> along when Trove got started but that’s not the case today and we have an
> opportunity to fix that now
> - A similarly significant portion of what Trove does is to implement a
> state-machine that will perform specific workflows involved in implementing
> database specific operations. This makes the Trove taskmanager a stateful
> entity. Some of the operations could take a fair amount of time. This is a
> serious architectural flaw
> - Tenants should not ever be able to directly interact with the underlying
> storage and compute used by database instances; that should be the default
> configuration, not an untested deployment alternative
> - The CI should test all databases that are considered to be ‘supported’
> without excessive use of resources in the gate; better code modularization
> will help determine the tests which can safely be skipped in testing changes
> - Clusters should be first class citizens not an afterthought, single
> instance databases may be the ‘special case’, not the other way around
> - The project must provide guest images (or at least complete tooling for
> deployers to build these); while the project can’t distribute operating
> systems and database software, the current deployment model merely impedes
> adoption
> - Clusters spanning OpenStack deployments are a real thing that must be
> supported
> This might sound harsh, that isn’t the intent. Each of these is the
> consequence of one or more perfectly rational decisions. Some of those
> decisions have had unintended consequences, and others were made knowing
> that we would be incurring some technical debt; debt we have not had the
> time or resources to address. Fixing all these is not impossible, it just
> takes the dedication of resources by the community.
> I do not have a complete design for what the new Trove would look like.
> For example, I don’t know how we will interact with other projects (like
> Heat). Many questions remain to be explored and answered.
> Would it suffice to just use the existing Heat resources and build
> templates around those, or will it be better to implement custom Trove
> resources and then orchestrate things based on those resources?
> Would Trove implement the workflows required for multi-stage database
> operations by itself, or would it rely on some other project (say Mistral)
> for this? Is Mistral really a workflow service, or just cron on steroids? I
> don’t know the answer but I would like to find out.
> While we don’t have the answers to these questions, I think this is a
> conversation that we must have, one that we must decide on, and then as a
> community commit the resources required to make a Trove v2 which delivers
> on the mission of the project; “To provide scalable and reliable Cloud
> Database as a Service provisioning functionality for both relational and
> non-relational database engines, and to continue to improve its
> fully-featured and extensible open source framework.”[2]
> Thanks,
> -amrith​
> [1] *https://www.openstack.org/assets/survey/April2017SurveyReport.pdf*
> <https://www.openstack.org/assets/survey/April2017SurveyReport.pdf>
> [2] *https://wiki.openstack.org/wiki/Trove#Mission_Statement*
> <https://wiki.openstack.org/wiki/Trove#Mission_Statement>
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