[openstack-dev] [all][tc] Languages vs. Scope of "OpenStack"
ben at swartzlander.org
Wed May 25 19:43:00 UTC 2016
On 05/25/2016 06:48 AM, Sean Dague wrote:
> I've been watching the threads, trying to digest, and find the way's
> this is getting sliced doesn't quite slice the way I've been thinking
> about it. (which might just means I've been thinking about it wrong).
> However, here is my current set of thoughts on things.
> 1. Should OpenStack be open to more languages?
> I've long thought the answer should be yes. Especially if it means we
> end up with keystonemiddleware, keystoneauth, oslo.config in other
> languages that let us share elements of infrastructure pretty
> seamlessly. The OpenStack model of building services that register in a
> service catalog and use common tokens for permissions through a bunch of
> services is quite valuable. There are definitely people that have Java
> applications that fit into the OpenStack model, but have no place to
> collaborate on them.
> (Note: nothing about the current proposal goes anywhere near this)
> 2. Is Go a "good" language to add to the community?
> Here I am far more mixed. In programming language time, Go is super new.
> It is roughly the same age as the OpenStack project. The idea that Go and
> Python programmers overlap seems to be because some shops that used
> to do a lot in Python, now do some things in Go.
> are things that go back 2 decades. Unless you have avoided Linux or the
> Web successfully for 2 decades, you've done these in some form. Maybe
> not being an expert, but there is vestigial bits of knowledge there. So
> they *are* different. In the same way that C or Java are different, for
> having age. The likelihood of finding community members than know Python
> + one of these is actually *way* higher than Python + Go, just based on
> duration of existence. In a decade that probably won't be true.
Thank you for bringing up this point. My major concern boils down to the
likelihood that Go will never be well understood by more than a small
subset of the community. (When I say "well understood" I mean years of
experiences with thousands of lines of code -- not "I can write hello
You expect this problem to get better in the future -- I expect this
problem to get worse. Not all programming languages survive. Google for
"dead programming languages" some time and you'll find many examples.
The problem is that it's never obvious when the languages are young that
something more popular will come along and kill a language.
I don't want to imply that Golang is especially likely to die any time
soon. But every time you add a new language to a community, you increase
the *risk* that one of the programming languages used by the community
will eventually fall out of popularity, and it will become hard or
impossible to find people to maintain parts of the code.
I tend to take a long view of software lifecycles, having witnessed the
death of projects due to bad decisions before. Does anyone expect
OpenStack to still be around in 10 years? 20 years? What is the
likelihood that both Python and Golang are both still popular languages
then? I guarantee  that it's lower than the likelihood that only
Python is still a popular language.
Adding a new language adds risk that new contributors won't understand
some parts of the code. Period. It doesn't matter what the language is.
My proposed solution is to draw the community line at the language
barrier line. People in this community are expected to understand
Python. Anyone can start other communities, and they can overlap with
ours, but let's make it clear that they're not the same.
 For all X, Y in (0, 1): X * Y < X
> 3. Are there performance problems where python really can't get there?
> This seems like a pretty clear "yes". It shouldn't be surprising. Python
> has no jit (yes there is pypy, but it's compat story isn't here). There
> is a reason a bunch of python libs have native components for speed -
> numpy, lxml, cryptography, even yaml throws a warning that you should
> really compile the native version for performance when there is full
> python fallback.
> The Swift team did a very good job demonstrating where these issues are
> with trying to get raw disk IO. It was a great analysis, and kudos to
> that team for looking at so many angles here.
> 4. Do we want to be in the business of building data plane services that
> will all run into python limitations, and will all need to be rewritten
> in another language?
> This is a slightly different spin on the question Thierry is asking.
> Control Plane services are very unlikely to ever hit a scaling concern
> where rewriting the service in another language is needed for
> performance issues. These are orchestrators, and the time spent in them
> is vastly less than the operations they trigger (start a vm, configure a
> switch, boot a database server). There was a whole lot of talk in the
> threads of "well that's not innovative, no one will want to do just
> that", which seems weird, because that's most of OpenStack. And it's
> pretty much where all the effort in the containers space is right now,
> with a new container fleet manager every couple of weeks. So thinking
> that this is a boring problem no one wants to solve, doesn't hold water
> with me.
> Data Plane services seem like they will all end up in the boat of
> "python is not fast enough". Be it serving data from disk, mass DNS
> transfers, time series database, message queues. They will all
> eventually hit the python wall. Swift hit it first because of the
> maturity of the project and they are now focused on this kind of
> optimization, as that's what their user base demands. However I think
> all other data plane services will hit this as well.
> Glance (which is partially a data plane service) did hit this limit, and
> the way it is largely mitigated by folks is by using Ceph and exposing that
> directly to Nova so now Glance is only in the location game and metadata
> game, and Ceph is in the data plane game.
> When it comes to doing data plan services in OpenStack, I'm quite mixed.
> The technology concerns for data plane
> services are quite different. All the control plane services kind of
> look and feel the same. An API + worker model, a DB for state, message
> passing / rpc to put work to the workers. This is a common pattern and
> is something which even for all the project differences, does end up
> kind of common between parts. Projects that follow this model are
> debuggable as a group not too badly.
> 5. Where does Swift fit?
> This I think has always been a tension point in the community (at least
> since I joined in 2012). Swift is an original service of OpenStack, as
> it started as Swift and Nova. But they were very different things. Swift
> is a data service, Nova was a control plane. Much of what is now
> OpenStack is Nova derivative in some way (some times direct extractions
> (Glance, Cinder, Ironic), some times convergent paths (Neutron). And
> then with that many examples, lots of other things built in similar ways.
> Swift doesn't use common oslo components. That actually makes debugging
> it quite different compared to the rest of OpenStack. The lack of
> oslo.log means structured JSON log messages to Elastic Search, are not
> a thing. Swift has a very different model in it's service split.
> Swift doesn't use global requirements. Swift ensures it can run without
> Keystone, because their goal is Swift everywhere, whether or not it's
> part of the rest of OpenStack.
> These are all fine goals, but they definitely have led to tensions on
> all sides.
> And I think part of the question is "are these tensions that need to be
> solved" or "is this data that this thing is different". Which isn't to
> say that Swift is bad, it's just definitively different than much of the
> ecosystem. Maybe Swift should be graduated beyond OpenStack, because
> it's scope cross cuts much differently. Ceph isn't part of OpenStack,
> but it's in 50% of installs. libvirt isn't part of OpenStack, but it's
> in 90% of installs. And in both of those cases OpenStack is one of the
> biggest drivers of their use.
> Which, gets contentious because people feel like this is kicking
> something out. And that I can understand. There is a lot of emotion
> wrapped up in labels and who gets to be on the the OpenStack home page.
> I wish there wasn't. Good software should get deployed because it is
> good and solves a need, not because of labels. I'm not sure Swift users
> really care that Swift is OpenStack. They care that Swift is Swift. And
> Swift being Swift, but not being OpenStack would open up degrees of
> freedom in Swift being more Swift centric without the same friction
> from the rest of of the ecosystem.
> Honestly, we probably need to just address #5 first and foremost. It's
> been dodged around for a long time, the tensions haven't gotten any better.
> We have just decided the standoff around Swift being different is going
> to remain.
> The global requirements proposal is a good example of that
> https://review.openstack.org/#/c/88736/ - 434 revisions later.
> From that we have one data point on #4. Are we going to be building a
> set of data plane services that can't be in python? If Swift wasn't the
> example here would we be having the conversation at all?
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