Atlanta PTG Reflections

Last week was the first-ever OpenStack PTG (Project Teams Gathering), held in Atlanta, Georgia. Let’s start with the obvious: the name is terrible, which made it very hard to explain to people (read: management at your job) what it was supposed to be, and why it was important. “The Summit” and “The Midcycle” were both much better in that regard. Yes, there was plenty of material available on the website, but a catchier name would have helped.

But with that said, it was probably one of the most productive weeks I’ve had as a OpenStack developer. In previous gatherings there were always things that were in the way. The Summits were too “noisy”, with all the distractions of keynotes, marketplace, presentations, and business /marketing people all over the place. The midcycles were much more focused on developer issues, but since they were usually single-team events, that meant very little cross-project interaction. The PTG represented the best of both without their downsides. While I always enjoyed Summits, there was a bunch of stuff always going on that distracted from being able to focus on our work.

The first two days were devoted to cross-project matters, and the API Working Group sure fits that description, as our goal is to help all OpenStack projects develop clean, consistent APIs. So as a core member of the API-WG, I was prepared to spend most of my time in these discussions. However, on Monday morning our room was fairly empty, although this was probably due to the fact that we weren’t scheduled a room until the night before, so not many people knew about it. So we all pecked at our laptops for an hour or so, and then I just figured we’d start. The topic was the changes to the API stability guidelines to define what the assert:supports-api-compatibility tag a project could aim for. I outlined the basic points, and Chris Dent filled in some more details. I was afraid that it might end up being Chris and I doing most of the talking, but people started adding their own points of view on the matter. Before long the room became more crowded; I think the lively discussion attracted people (well, that and the sign that Chris added in the hallway!).

The gist of the discussion was just how strict we needed to be about when changing some aspect of a public API required a version change. Most of the people in the room that morning were of the opinion that while removing an API or changing the behavior of a call would certainly require a change, non-destructive changes like adding a new API call, or adding an additional field to a response, should be fine without a version change, since they shouldn’t break anything. I tried to make the argument for interop API stability, but I was outnumbered 🙂 Fortunately, I ran into the biggest (and loudest! 🙂 proponent for that, Monty Taylor, at lunch, and convinced him to come to the afternoon session and make his point of view heard clearly. And he did exactly that! By the end of the afternoon, we were all in agreement that any change to any API call requires a version increase, and so we will update the guidelines to reflect that.

Tuesday was another cross-project day, with discussions on hierachical quotas taking up a lot of the morning, followed by a Nova-Neutron session and another session with the Cinder folks on multi-attach. What was consistent across these sessions was a genuine desire to get things working better, without any of the finger-pointing that could certainly arise when two teams get together to figure out why things aren’t as smooth as they should be.

Wednesday began the team-specific sessions. Nova was given a huge, cavernous ballroom. It had a really bad echo, as well as constant fan noise from the air system, and so for someone like me with hearing loss, it was nearly impossible to hear anything. Wish I had worked on my lip reading!

The cavernous ballroom as originally set up for the Nova team sessions.

We quickly decided to re-arrange the tables into a much more compact structure, which made it slightly better for discussions.

Moving the tables into a smaller rectangle made it a little easier to hear each other.

We had a full agenda, with topics such as cells V2, quotas, and the placement engine/API pretty much taking up Wednesday and Thursday. And like the cross-project days, it felt like we made solid progress. Anyone who had their doubts about this new format were convinced by now that the PTG was a big improvement! The discussions about Placement were especially helpful for me, because we went into the details of the complex nesting possibilities of NUMA cells and SR-IOV devices, and what the best way (if any) to effectively model them would be.

There was one dark spot on the event: my laptop died a horrible death! Thursday morning I opened the lid that I had closed a few hours earlier after an evening of email answering and Netflix watching, only to be greeted with this:

You do NOT want your laptop screen to look like this!

It had made a crackling sound as the screen displayed kernel panic output, so I unplugged the charger and closed the lid. After waiting several anxious minutes, I tried to turn the laptop on. Nothing. Dead. No response at all: no sound, no video… nothing. I tried again and again, using every magical keypress incantation I knew, and nothing. Time of death: 0730.

Sure, I still had my iPhone, but it’s really hard to do serious work that way. For one, etherpads simply don’t work in iOS browsers. It’s also very hard to see much of a conversation in an IRC client on such a small screen. All I could do was read email. So I spent the rest of the PTG feeling sorry for myself and my poor dead laptop. David Medberry lent me his keyboard-equipped Kindle for a while, and that was a bit better, but still, when you have a muscle-memory workflow, nothing will replace that.

The Foundation also arranged to have team photos taken during the PTG. You can see all the teams here, but I thought I’d include the Nova team photo here:

The Nova Team at the Pike PTG

Right after the last session on Thursday was a feedback session for the OpenStack Foundation to get the attendees’ impressions of what went well, what was terrible, what should they keep doing, what should the never ever do again, and everything in between. In general, most people liked the PTG format, and felt that it was a very productive week. There were many complaints about the hotel setup (room size, noisy AC, etc.), as well as disappointment in the variety of meals and lack of snacks, but lots of praise for the continuous coffee!!

Thursday night was the Nova team dinner. We went to Ted’s Montana Grill, where we were greeted by a somewhat threatening slogan:

Hmmm… are you threatening me???

The staff wasn’t threatening at all, and quickly found tables for all of us. On the way through the restaurant we passed several other tables of Stackers, so I guess that this was a popular choice. We had a wonderful dinner, and on the walk home, Chet Burgess, whose parents still live in the Atlanta area, suggested we stop at the Westin hotel for a quick drink. That sounded great to me, so four of us went into the hotel. I was surprised that Chet walked right past the bar, and went to the elevators. Turns out that there is a rotating bar up on the 73rd floor! Here is the group of us going up the elevator:

Top: John Garbutt, Tony Breeds. Bottom: Chet Burgess and Yours Truly

It was dark in the bar area, so I couldn’t get a nice photo, but here’s a stock photo to give you an idea of what the bar looked like:

The Sundial Bar at the Westin Hotel

Big thanks to Chet for organizing the dinner and suggesting having drinks up in the heights of Atlanta!

Friday was a much lower-key day. Gone were the gigantic ballrooms, and down to the lower level of the hotel for the final day. Many people had left already, as many teams did not schedule 3 full days of sessions. The Nova team used the first part of the day to go over the Ocata retrospective to talk about what went well, what didn’t go so well, and how we can improve as we start working on Pike. The main points were that while communication among the developers was better, it still needed to improve. We also agreed on the need for more visual documentation of the logic flows within the code. The specs only describe the surface of the design, and many people (like myself) are visual learners, so we’ll try to get something like that done for the Placement logic so that everyone can better understand where we are and where we need to go.

I had to leave around 4pm on Friday to catch my flight home, so I headed to the ATL airport. While walking through the terminal I saw a group of men standing in one of the hallways, and recognized that one of them was Rep. John Lewis, one of the leaders of the Civil Rights movement along with Dr. Martin Luther King, Jr., whose birthplace and historic site I visited earlier in the week. I shook his hand, and thanked him for everything that he has done for this country. Immediately afterwards I texted my wife to tell her about it, and she chastised me for not getting a photo! I explained that I was too nervous to impose on him. A little while later I walked over to another part of the airport where I knew there was a restroom, since I had to empty my water bottle before going through security. When I got there, I saw some of the same group of men I had seen with Rep. Lewis earlier, but he was no longer among them. Then I looked over by the entrance to the men’s room, and I saw Rep. Lewis posing for a selfie with the janitor! I figured he wouldn’t mind taking one with me, so when he came out I apologized for bothering him again, and asked if he would mind a photo. He smiled and said it was no problem, so…

Ran into one of the great American heroes, Representative John Lewis, in the Atlanta airport. He was gracious enough to let me take this photo.

I admit that I was too excited to hold the phone very still! So a blurry photo is still better than no photo at all, right? I’ve met several famous people in my lifetime, but never one who has done as much to make the world a better place. And looking back, it was a fitting end to a week that involved the coming together of people of different nationalities, races, religions to help build a free and open software.

OpenStack Focus

There has been a bit of concern expressed lately that OpenStack is somehow losing its focus, and is in danger of losing its momentum because of the effect of the Big Tent, and its  resulting growth in the number of projects that call themselves OpenStack. This growth has even been blamed for the recent layoffs of OpenStack developers. Some have called on the OpenStack leadership to dismantle the Big Tent approach, and only focus on a few core projects.

While it is true that the plethora of projects has diverted attention from the work needed in the heart of OpenStack (and I won’t go into how to draw the line separating the two here), I feel that the criticism is misplaced. It isn’t up to the governing bodies of OpenStack to enforce such a refocusing; rather, it is up to the contributors to make such decisions. That’s just the way that open source development works. It is silly to think that companies like HPE would take their marching orders from the OpenStack Foundation Board, or the OpenStack TC. The idea of the Big Tent, that all projects that are “one of us” shall have access to the same resources, is fine as it is.

The mistake that I believe many companies made is that they tried to focus on beefing up numbers that are irrelevant, such as lines of code, or the number of cores or PTLs they employed, as a way of demonstrating their commitment to OpenStack. They then would use those numbers for their sales teams as a selling point for their OpenStack-based offerings.

Open Source is a difficult sell for most companies; they certainly understand the benefit when they use it, but have a much harder time justifying the cost of paying their employees to work on something that is used by everyone, even their competitors. So they came up with ways of selling their particular spin on OpenStack, and used these contribution number to impress customers. So when that failed to generate the type of revenue that was expected, out came the axe.

I believe that many of these companies encouraged the development of these small peripheral projects because it would be easier for one of their employees to achieve core status, and possibly get elected PTL, which their marketing departments would use in an attempt to prove that company’s OpenStack-ness.

I don’t agree that there is anything that OpenStack itself needs to do. Rather, the companies who are contributing to OpenStack need to better understand the nature of open source development, and focus on those areas that will make OpenStack as a whole richer and more reliable, instead of gaming the system to make themselves look important. So please stop saying that this is the fault of the Big Tent.

Pair Development

If you’ve worked on large open source projects, one of the difficulties is dividing the workload. The goal, of course, is to spread it out so that every developer has a workload that will keep them busy, and everyone is working in sync towards a common goal. This isn’t easy in practice, as there is no top-down authority to hand out assignments and keep everyone on track, as there is in a corporate development environment. It requires a good deal of communication among the members of the team, as well as a good deal of trust.

This problem was brought to light recently in the Nova community. The issue was with the subteam working on the scheduler/placement engine, of which I’m a member. During the Newton development cycle, there was a significant bottleneck due to the fact that one person, Chris Dent, was responsible for a large chunk of work in designing and coding the Placement API and underlying engine, while the rest of us could only help by doing reviews after the code was written. And this isn’t a new thing: during Mitaka, it was Jay Pipes who was the bottleneck with the development of the Resource Providers concept, and in Liberty, it was Sylvain Bauza with the huge amount of work he did to integrate the Request Spec into Nova. Don’t get me wrong: I’m not criticizing any of these people, as they all did great work. Rather, I am expressing frustration that they bore the brunt of the load, when it didn’t have to be that way. I think that it is time to try a different approach in Ocata.

I propose that we use Pair Development. No, not Pair Programming – that’s an entirely different thing. Pair Development is when each “chunk” of work is not undertaken by a single developer, but rather to two. They discuss the path they want to take ahead of time, and instead of splitting the work, they both work on the same patches at the same time. Wait, you say – won’t this slow things down? I don’t believe that it will, for several reasons. First, when discussing a design, having multiple sets of eyes will reduce the number of dead ends, in the same way that bugs are reduced in pair programming by having both developers review the code as it is being written. Second, when a reviewer finds an issue with a patch, either developer can make the fix. This is an even greater benefit if the two developers are in different, but overlapping, time zones.

We also have as evidence the week before the most recent Feature Freeze: the placement stuff needed to get in before FF, and so a whole group of us pulled together to make that happen. Having a diverse set of eyes uncovered several edge cases and inconsistencies in the code, and those were resolved pretty quickly. We used IRC mostly, but had a Google Hangout at least once a day to discuss any outstanding, unresolved matters, so that we would all be on the same page. So yeah, the time pressure helped instill a bit of urgency in us all, but I think that it was having all of us own the code, not just Chris, that made things happen as well as they did. I know that I was familiar with the code, having reviewed much of it before, but now that I had to change it and test it myself, my understanding grew much deeper. It’s amazing how deeper you understand something when you touch it instead of just look at it.

Another benefit of pair development is that it provides much more continuity when one of the developers takes some time off. Instead of the progress getting put on hold, the other member of the development pair can continue along. It will also help to have more than one person know the new code intimately, so that when a behavior surfaces that is not expected, we aren’t depending on a single person to figure out what’s going on.

So for Ocata, let’s figure out the tasks, and make sure that each has two people assigned to it. I will wager that come the end of the cycle, it will help us accomplish much more than we have in previous releases.

Is Swift OpenStack?

There has been some discussion recently on the OpenStack Technical Committee about adding Golang as a “supported” language within OpenStack. This arose because the Swift project had recently run into some serious performance issues, which they solved by re-writing the bottleneck process in Golang with much success. I’m not writing here to debate the merits of making OpenStack more polyglot (it’s no secret that I oppose that), but instead, I want to address the issue of Swift not behaving like the rest of OpenStack.

Doug Hellman summarized this feeling well, originally writing it in a pastebin, but then copying it into a review comment on the TC proposal. Essentially, it says that while Swift makes some efforts to do things the “OpenStack Way”, it doesn’t hesitate to follow its own preferences when it chooses to.

I believe that there is good reason for this, and I think that people either don’t know or forget a lot of the history of OpenStack when they discuss Swift. Here’s some background to clarify:

Back in the late ’00s, Rackspace had a budding public cloud business (note: I worked for Rackspace from 2008-2014). It had bought Slicehost, a company with a closed-source VPS system that it used as the basis for its Cloud Servers product, and had developed a proprietary object storage system called NAST (Not Another S Three: S3, get it?). They began hitting limits with NAST fairly soon – it was simply too slow. So it was decided to write a new system with scalability in mind that would perform orders of magnitude better than NAST; this was named ‘Swift’ (for obvious reasons). Swift was developed in-house as a proprietary software project. The development team was a small, close-knit group of guys who had known each other for years. I joined the Swift development team briefly in 2009, but as I was the only team member working remotely, I was at a significant disadvantage, and found it really difficult to contribute much. When I learned that Rackspace was forming a distributed team to rewrite the Cloud Servers software, which was also beginning to hit scalability limits, I switched to that team. For a while we focused on keeping the Slicehost code running while starting to discuss the architecture of the new system. Meanwhile the Swift team continued to make strong progress, releasing Swift into production in the spring of 2010, several months before OpenStack was announced.

At roughly the same time, the other main part of OpenStack, Nova, was being started by some developers working for NASA. It worked, but it was, shall we say, a little rough in spots, and lacked some very important features. But since Nova had a lot of the things that Rackspace was looking for, we started talking with NASA about working together, which led to the creation of OpenStack. So while Rackspace was a major contributor to Nova development back then, from the beginning we had to work with people from a wide variety of companies, and it was this interaction that formed the basis of the open development process that is now the hallmark of OpenStack. Most of the projects in OpenStack today grew out of Nova (Glance, Neutron, Cinder), or are built on top of Nova (Trove, Heat, Watcher). So when we talk about the “OpenStack Way”, it really is more accurately thought of as the “Nova” way, since Nova was only half of OpenStack. These two original halves of OpenStack were built very differently, and that is reflected in their different cultures. So I don’t find it surprising that Swift behaves very differently. And while many more people work on it now than just the original team from Rackspace, many of that original team are still developing Swift today.

I do find it somewhat strange that Swift is being criticized for having “resisted following so many other existing community policies related to consistency”. They are and always have been distinct from Nova, and that goes for the community that sprang up around Nova. It feels really odd to ignore that history, and sweep Swift’s contributions away, or disparage their team’s intentions, because they work differently. So while I oppose the addition of languages other than Python for non-web and non-shell programming, I also feel that we should let Swift be Swift and let them continue to be a distinct part of OpenStack. Requiring Swift to behave like Nova and its offspring is as odd a thought as requiring Nova et. al. to run their projects like Swift.

OpenStack Ideas

I’ve written several blog posts about my ideas for improving OpenStack, with a particular emphasis on the Nova Scheduler. This week at the OpenStack Summit in Austin, there were two other proposals put forth. So at least I’m not the only one thinking about this stuff!

At the Tuesday keynote, Intel demonstrated a version of OpenStack that was completely re-written in Go. They demonstrated creating 10,000 containers and 5,000 VMs in under a minute. Pretty impressive, right? Well, yeah, except they gave no idea of what parts of Nova were supported, and what was left out. How were all those VMs scheduled? What sort of logging was done to help operators diagnose their sites? None of this was shown or even discussed. It didn’t seem to be a serious proposal for moving OpenStack forward; instead, it seemed that it was a demo with a lot of sizzle designed to simply wake up a dormant community, and make people think that Intel has the keys to our future. But for me, the question was always the same one I deal with when I’m thinking about these matters: how do you get from the current OpenStack to what they were showing? Something tells me that rather than being a path forward, this represents a brand-new project, with no way for existing deployments to migrate without starting all over. So yeah, kudos on the demo, but I didn’t see anything directly useful in it. Of course Go would be faster for concurrent tasks; that’s what the language was designed for!

The other project was presented by a team of researchers from Inria in France who are aiming to build a massively-distributed cloud with OpenStack. Instead of starting from scratch as Intel did, they instead created a driver for oslo.db that mimicked SQLAlchemy, and used Redis as the datastore. It’s ironic, since the first iteration of Nova used Redis, and it was felt back then that Redis wasn’t up to the task, so it was replaced by MySQL. (Side note: some of my first commits were for removing Redis from Nova!) And being researchers, they meticulously measured the performance, and when sites were distributed, over 80% of the queries performed better than with MySQL. This is an interesting project that I intend on following in the future, as it actually has a chance of ever becoming part of OpenStack, unlike the Intel project.

I still hold out hope that one day we can free ourselves of the constraints of having to fit all resources that OpenStack will ever have to deal with into a static SQL model, but until then, I’m happy with whatever incremental improvements we can make. It was obvious from this Summit that there are a lot of very smart people thinking about these issues, too, and that fills me with hope for the long-term health of OpenStack.