rjbs forgot what he was saying

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first impressions of ActiveState Stackato

by rjbs, created 2011-08-25 19:52
tagged with: @markup:md cloud journal perl programming

When Heroku started to become popular, I thought it was pretty neat, but not neat enough to get me to change my primary development language. A year or two ago, a friend asked if I was interested in helping develop "Heroku for Perl." I said I didn't see much value in it for myself. I knew how to deploy applications "the hard way," so investing in making it easier didn't win me much. This year, a few PaaS providers supporting Perl have shown up, and I didn't pay them any attention until someone told me that ActiveState's Stackato cloud system was having a contest and that I should consider entering it.

To cut a long story short: I gave it a go, and my opinion has changed. This kind of deployment definitely has potential, maybe even for set-in-their-ways people like me. Stackato needs more work before its beta period can be over, but it's way cool, and has a lot of potential.

The following is more of the long story:

I've read almost nothing about Stackato, including the ActiveState site about it. I know practically nothing about what it's really intended to be or how ActiveState imagines it being used or its future. I only read the pages that looked like they'd help me get my project up and running, and nothing that looked like it was designed to convince me to use Stackato. My mission was to win the contest, not to decide whether to use Stackato for my business.

The one piece of marketing text that I did read, as I'd seen it a few places, was this: Simply install Stackato, then deploy and run your applications in the cloud in less than 15 minutes. I was shocked by how close to true that turned out to be. I had to fumble around a few times when I hit snags that were sometimes my fault and sometimes Stackato's, but if I had known what I was doing and if Stackato had been just slightly tweaked to start, I think the slogan would've been true -- and that's pretty impressive.

The contest was to bring up an open-source web application on Stackato. At first, I thought I'd have to write something new, which seemed like a big drag. I found out that I could use an existing program, whcih was great news. It also helped me focus on understanding Stackato instead of writing a web app. If I had written a new app, the easy deployment wouldn't have made any impact, because I would've been spending all my time debugging new code. I decided to get Rubric up and running. It's sort of dated in its underlying code, but it works well and has obvious uses. I still use it, seven years after writing it, and am not disgusted by it. It seemed like a good starting point.

Here's a rough outline of everything I knew I had to do -- and note that some of these commands might be slightly off:

  1. download the VMWare image and start up the machine in VMWare Fusion
  2. put an app.psgi file in my git repo's root
  3. run stackato target stackato.local
  4. run stackato push from my working directory
  5. visit my app on the web

This actually went a lot better than I expected it to, but it did fail. Why? I had nearly no idea. The Stackato client offers much too little visibility into what's going on with your deployment. It tries to offer enough, but here and there -- especially during initial deployment -- it fails. For example, you can tail log files with the Stackato client, but you can only access them on a per-deployed-application basis. Once you've finished deploying, this is fine. When you're in the middle of deploying, though, you can't get at the files. That means you can't tail the results of staging your prereqs during initial deployment, which is where I hit many of my problems. Now, it turns out there was a way to get at those logs: log into a shell on the VM, look at the output of ps auxww, find the file under /tmp to which cpanm output is being piped, and tail that. Unfortunately, once you have to log into the VM, something is wrong. Everything should work without the developer needing to do that.

The good news is that this seems pretty easy to fix. The client should make these logs easier to find and access during deployment or after a failed deployment. This doesn't seem like a design problem, just an unfinished feature.

Incidentally, there was another rough edge that drove me much crazier than it needed do. When deploying an app, there is a "staging" phase during which CPAN prereqs are installed. Rubric has quite a few prereqs, so this phase takes a while. Unfortunately, the indicator that staging has begun is not printed properly, meaning that while staging is happening, the client would show "stopping application." I kept wondering why my application wouldn't shut down clearly -- well, it turns out it stopped just fine, and then staging began. I would've been much more patient with staging.

So, why did I need to keep looking at my staging logs? There were a few reasons, each less annoying than the first. The first problem was probably most annoying because I hit it first, while I felt like I was on a roll, and it slowed me down. Stackato is supposed to determine your prereqs from your Makefile.PL, but mine kept failing to provide any. Rubric uses Module::Install for its config tool, and I wasn't pushing up the inc directory that gets built into released distributions. Stackato doesn't come with Module::Install pre-installed, so my Makefile.PL relied on code that was neither bundled nor installed. The lesson here is that Stackato expects something more like a dist than like a working tree.

Rather than convert my install tool, I noticed something telling me that I could provide a requirements.txt. What's that? I had no idea, and there were no links to documentation for it, so I took a wild guess. I put each prereq (with no version information) on its own line in the file and pushed that. I knew it was working when it took ages. Like I said, I have a load of prereqs, and I was just fine with the expense of installing them all.

Pretty soon, Stackato reported success, and I was amazed. Really? Everything just worked? It told me I could find my application at http://rubric.stackato.local -- and this detail delighted me to no end. See, when you bring up an application on your virt, it adds a new mDNS name for that application, so it just shows up -- no path prefix, no stupid port names, no nothing. I hope I can find a way to do this with my local testing of Plack stuff. It was a small detail, but a really, really slick one.

Unfortunately, hitting that URL got me an empty page. Where was the drab, hacker-produced HTML I expected? I looked at the logs. Now that I'd finished deploying, they were there and easy to access. The only thing in them, though, was a warning about doing a undef > 0 comparison in a template. This was driving me nuts! If my templates were being rendered, why wasn't I seeing them?

At this point, it was getting late, so I turned in for the night and didn't get back to things for another day or two. (I was busy with D&D.) Once I did get back, though, the problem was still there. Fortunately, as is often the case, IRC had the answer for me: the Stackato HTTP server was not happy unless it got a Content-Length header. I added the ContentLength middleware and there was Rubric, looking right at me. I had pushed up my personal Rubric database, and everything worked: I could log in, post new entries, and browse existing ones. The only problem was the lack of any CSS. I'll come back to that in a bit.

First, though, imagine that I hadn't been using Module::Install -- it's used by about 15% of CPAN dists -- but instead was using Module::Build or ExtUtils::ModuleMaker, which are used by nearly all of the remaining 85%. Then imagine that I'd already had the ContentLength middleware in place, which I should've, if I was being more careful. If I had, then I probably would've actually had the application up and running in about fifteen minutes. I realized this immediately, and it was quite impressive.

But what was going on with that CSS? Why wasn't it showing up? After all, the way CSS in Rubric works is simple: requests under /style look for files under the same directory in the dist's share directory. Thinking about that made it clear: my share files weren't being installed, because Stackato does not install your application, it just runs it. So, even though it seems like it expects a dist, even that is not quite right. What it really wants is much, much less: just the app.psgi and needed support files.

This was sort of a revelation. I deleted almost everything from my working tree and pushed a tiny requirements.txt requesting only Rubric. So, my working tree was now basically this:

app.psgi          - tiny file, the Rubric PSGI app
requirements.txt  - one line containing "Rubric"
rubric.db         - an SQLite file with the data in it
rubric.yml        - the site configuration

I could've even skipped the database, if I wanted to run the "build a db file" program after deployment, but it seemed harmless to keep it around. I pushed this -- and waited a few minutes while it redeployed -- and pretty soon the site was up and running, with CSS. I would've started with this from the beginning, if the docs had made it clear that this was the way to go, and things would've been even better after the 15 minute deployment. (Maybe the docs do suggest this, somewhere. As I said, I barely read them.)

So, I sent off my note to ActiveState. I didn't think I had much of a chance, because I'd spent so little time on it. On the other hand, Rubric is a pretty nice application, and I thought it was pretty impressive to see that even something as full-featured as it could be deployed so easily.

The next day, I got a note from ActiveState -- they didn't know how to add users, and I'd provided only the barest minimum of instructions. I said they'd have to run something like this:

$ stackato run rubric rubric user --new-user \
  --email user@example.com
  --pass  secret
  username

...but this wasn't working. It turns out that they'd found a bug in Rubric! I hadn't used --new-user in years, and in the meantime, I'd added a bug to it. And I didn't have a test for it. How embarassing! I immediately made a fix and deployed that to the CPAN.

Now I hit another problem: requirements.txt finds things to install by looking at ActiveState's PPM repository. I can't force it to get the latest from CPAN. For that, I have to use a Makefile.PL, which will use cpanm. I thought I could sidestep this by using stackato run rubric cpanm Rubric, but it turns out that you can't use the Stackato client to run cpanm in the context of your app. This is actually probably a really good thing, because it keeps you from sidestepping the normal deployment procedure. I bit the bullet and spent sixty seconds writing a new Makefile.PL, using ExtUtils::MakeMaker. I re-deployed, it picked up Rubric 0.148, with the bugfix, and now adding users worked. Awesome!

If you want to see it, my deployment repository is on GitHub. The head as of this posting was 5227cbb0.

There was one other problem I hit. At one point, deployment failed halfway through because of the loathsome live tests for WWW::Mechanize. Sure, they are optional: you can supply a --no-live switch when configuring it -- but you have no access to that when deploying with cpanm. I suggested that Stackato could use CPAN.pm, and ship with ActiveState-managed distroprefs to deal with just this sort of problem. I want most tests to run, but not tests that are so fickle.

So, if I wanted to use Stackato, what would my deployment strategy be? ActiveState doesn't seem to be planning to run their own public cloud. You'll have to have your own hardware running Stackato VMs, or maybe you'll be able to rent them from a cloud provider. How will this be billed? What is ActiveState actually going to sell to make money? I don't know, and for now, I don't care. I'm in no position to actually move our work applications to this, so I am content to sit back and relax and see what happens. Maybe in a year, when Stackato is a more mature, released product, it will all be clear and I'll even consider whether we'd like using it for real work. Until then, what I can say is that it was a fairly painless experience, and made me see how much utility a PaaS system can provide.