Good discussion, Zane. Comments inline.
On 06/20/2017 11:01 AM, Zane Bitter wrote:
On 20/06/17 10:08, Jay Pipes wrote:
On 06/20/2017 09:42 AM, Doug Hellmann wrote:
Does "service VM" need to be a first-class thing? Akanda creates
them, using a service user. The VMs are tied to a "router" which
is the billable resource that the user understands and interacts with
through the API.
Frankly, I believe all of these types of services should be built as
applications that run on OpenStack (or other) infrastructure. In other
words, they should not be part of the infrastructure itself.
There's really no need for a user of a DBaaS to have access to the
host or hosts the DB is running on. If the user really wanted that,
they would just spin up a VM/baremetal server and install the thing
themselves.
Hey Jay,
I'd be interested in exploring this idea with you, because I think
everyone agrees that this would be a good goal, but at least in my mind
it's not obvious what the technical solution should be. (Actually, I've
read your email a bunch of times now, and I go back and forth on which
one you're actually advocating for.) The two options, as I see it, are
as follows:
1) The database VMs are created in the user's tena^W project. They
connect directly to the tenant's networks, are governed by the user's
quota, and are billed to the project as Nova VMs (on top of whatever
additional billing might come along with the management services). A
[future] feature in Nova (https://review.openstack.org/#/c/438134/)
allows the Trove service to lock down access so that the user cannot
actually interact with the server using Nova, but must go through the
Trove API. On a cloud that doesn't include Trove, a user could run Trove
as an application themselves and all it would have to do differently is
not pass the service token to lock down the VM.
alternatively:
2) The database VMs are created in a project belonging to the operator
of the service. They're connected to the user's network through <magic>,
and isolated from other users' databases running in the same project
through <security groups? hierarchical projects? magic?>. Trove has its
own quota management and billing. The user cannot interact with the
server using Nova since it is owned by a different project. On a cloud
that doesn't include Trove, a user could run Trove as an application
themselves, by giving it credentials for their own project and disabling
all of the cross-tenant networking stuff.
None of the above :)
Don't think about VMs at all. Or networking plumbing. Or volume storage
or any of that.
Think only in terms of what a user of a DBaaS really wants. At the end
of the day, all they want is an address in the cloud where they can
point their application to write and read data from.
Do they want that data connection to be fast and reliable? Of course,
but how that happens is irrelevant to them
Do they want that data to be safe and backed up? Of course, but how that
happens is irrelevant to them.
The problem with many of these high-level *aaS projects is that they
consider their user to be a typical tenant of general cloud
infrastructure -- focused on launching VMs and creating volumes and
networks etc. And the discussions around the implementation of these
projects always comes back to minutia about how to set up secure
communication channels between a control plane message bus and the
service VMs.
If you create these projects as applications that run on cloud
infrastructure (OpenStack, k8s or otherwise), then the discussions focus
instead on how the real end-users -- the ones that actually call the
APIs and utilize the service -- would interact with the APIs and not the
underlying infrastructure itself.
Here's an example to think about...
What if a provider of this DBaaS service wanted to jam 100 database
instances on a single VM and provide connectivity to those database
instances to 100 different tenants?
Would those tenants know if those databases were all serviced from a
single database server process running on the VM? Or 100 contains each
running a separate database server process? Or 10 containers running 10
database server processes each?
No, of course not. And the tenant wouldn't care at all, because the
point of the DBaaS service is to get a database. It isn't to get one or
more VMs/containers/baremetal servers.
At the end of the day, I think Trove is best implemented as a hosted
application that exposes an API to its users that is entirely separate
from the underlying infrastructure APIs like Cinder/Nova/Neutron.
This is similar to Kevin's k8s Operator idea, which I support but in a
generic fashion that isn't specific to k8s.
In the same way that k8s abstracts the underlying infrastructure (via
its "cloud provider" concept), I think that Trove and similar projects
need to use a similar abstraction and focus on providing a different API
to their users that doesn't leak the underlying infrastructure API
concepts out.
Best,
-jay
Of course the current situation, as Amrith alluded to, where the default
is option (1) except without the lock-down feature in Nova, though some
operators are deploying option (2) but it's not tested upstream...
clearly that's the worst of all possible worlds, and AIUI nobody
disagrees with that.
To my mind, (1) sounds more like "applications that run on OpenStack (or
other) infrastructure", since it doesn't require stuff like the
admin-only cross-project networking that makes it effectively "part of
the infrastructure itself" - as evidenced by the fact that unprivileged
users can run it standalone with little more than a simple auth
middleware change. But I suspect you are going to use similar logic to
argue for (2)? I'd be interested to hear your thoughts.
cheers,
Zane.
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