You may have heard about Amazon’s newest offering they announced today, CloudFormation. It’s the new hotness, but I see a lot of confusion in the Twitterverse about what it is and how it fits into the landscape of IaaS/PaaS/Elastic Beanstalk/etc. Read what Werner Vogels says about CloudFormation and its uses first, but then come back here!
Allow me to break it down for you and explain why this is such a huge leverage point for cloud developers.
What Has Come Before
Up till now on Amazon you could configure up a single virtual image the way you wanted it, with an AMI. You could even kind of construct a scalable tier of similar systems using Auto Scaling, by defining Launch Configurations. But if you wanted to construct an entire multitier system it was a lot harder. There are automated configuration management tools like chef and puppet out there, but their recipes/models tend to be oriented around getting a software loadout on an existing system, not the actual system provisioning – in general they come from the older assumption you have someone doing that on probably-physical systems using bcfg2 or cobber or vagrant or something.
So what were you to do if you wanted to bring up a simple three tier system, with a Web tier, app server tier, and database tier? Either you had to set them up and start them manually, or you had to write code against the Amazon APIs to explicitly pull up what you wanted. Or you had to use a third party provisioning provider like RightScale or EngineYard that would let you define that kind of model in their Web consoles but not construct your own model programmatically and upload it. (I’d like my product functionality in my own source control and not your GUI, thanks.)
Now, recently Amazon launched Elastic Beanstalk, which is more way over on the PaaS side of things, similar to Google App Engine. “Just upload your application and we’ll run it and scale it, you don’t have to worry about the plumbing.” Of course this sharply limits what you can do, and doesn’t address the question of “what if my overall system consists of more than just one Java app running in Beanstalk?”
If your goal is full model driven automation to achieve “infrastructure as code,” none of these solutions are entirely satisfactory. I understand CloudFormation deeply because we went down that same path and developed our own system model ourselves as a response!
I’ll also note that this is very similar to what Microsoft Azure does. Azure is a hybrid IaaS/PaaS solution – their marketing tries to say it’s more like Beanstalk or Google App Engine, but in reality it’s more like CloudFormation – you have an XML file that describes the different roles (tiers) in the system, defines what software should go on each, and lets you control the entire system as a unit.
So What Is CloudFormation?
Basically CloudFormation lets you model your Amazon cloud-based system in JSON and then provision and control it as a unit. So in our use case of a three tier system, you would model it up in their JSON markup and then CloudFormation would understand that the whole thing is a unit. See their sample template for a WordPress setup. (A mess more sample templates are here.)
Review the WordPress template; it lets you define the AMIs and instance types, what the security group and ELB setups should be, the RDS database back end, and feed in variables that’ll be used in the consuming software (like WordPress username/password in this case).
Once you have your template you can tell Amazon to start your “stack” in the console! It’ll even let you hook it up to a SNS notification that’ll let you know when it’s done. You name the whole stack, so you can distinguish between your “dev” environment and your “prod” environment for example, as opposed to the current state of the Amazon EC2 console where you get to see a big list of instance IDs – they added tagging that you can try to use for this, but it’s kinda wonky.
Why Do I Want This Again?
Because a system model lets you do a number of clever automation things.
If you’ve been doing Amazon yourself, you’re used to there being a lot of stuff you have to do manually. From system build to system build even you do it differently each time, and God forbid you have multiple techies working on the same Amazon system. The basic value proposition of “don’t do things manually” is huge. You configure the security groups ONCE and put it into the template, and then you’re not going to forget to open port 23 AGAIN next time you start a system. A core part of what DevOps is realizing as its value proposition is treating system configuration as code that you can source control, fix bugs in and have them stay fixed, etc.
And if you’ve been trying to automate your infrastructure with tools like Chef, Puppet, and ControlTier, you may have been frustrated in that they address single systems well, but do not really model “systems of systems” worth a damn. Via new cloud support in knife and stuff you can execute raw “start me a cloud server” commands but all that nice recipe stuff stops at the box level and doesn’t really extend up to provisioning and tracking parts of your system.
With the CloudFormation template, you have an actual asset that defines your overall system. This definition:
- Can be controlled in source control
- Can be reviewed by others
- Is authoritative, not documentation that could differ from the reality
- Can be automatically parsed/generated by your own tools (this is huge)
It’s also nicely transparent; when you go to the console and look at the stack it shows you the history of events, the template used to start it, the startup parameters it used… Moving away from the “mystery meat” style of system config.
With CloudFormation, you can start and stop an entire environment with one operation. You can say “this is the dev environment” and be able to control it as a unit. I assume at some point you’ll be able to visualize it as a unit, right now all the bits are still stashed in their own tabs (and I notice they don’t make any default use of their own tagging, which makes it annoying to pick out what parts are from that stack).
This is handy for not missing stuff on startup and teardown… A couple weeks ago I spent an hour deleting a couple hundred rogue EBSes we had left over after a load test.
And you get some status eventing – one of the most painful parts of trying to automate against Amazon is the whole “I started an instance, I guess I’ll sit around and poll and try to figure out when the damn thing has come up right.” In CloudFront you get events that tell you when each part and then the whole are up and ready for use.
What It Doesn’t Do
It’s not a config management tool like Chef or Puppet. Except for what you bake onto your AMI it has zero software config capabilities, or command dispatch capabilities like Rundeck or mcollective or Fabric. Although it should be a good integration point with those tools.
It’s not a PaaS solution like Beanstalk or GAE; you use those when you just have an app you want to deploy to something that’ll run it. Now, it does erode some use cases – it makes a middle point between “run it all yourself and love the complexity” and “forget configurable system bits, just use PaaS.” It allows easy reusability, say having a systems guy develop the template and then a dev use it over and over again to host their app, but with more customization than the pure-play PaaSes provide.
It’s not quite like OVF, which is more fiddly and about virtually defining the guts of a single machine than defining a set of systems with roles and connections.
It’s very similar to Microsoft Azure’s approach with their .cscfg and .csdef files which are an analogous XML model – you really could fairly call this feature “Amazon implements Azure on Amazon” (just as you could fairly call Elastic Beanstalk “Amazon implements Google App Engine on Amazon”.) In fact, the Azure Fabric has a lot more functionality than the primitive Amazon events in this first release. Of course, CloudFormation doesn’t just work on Windows, so that’s a pretty good width vs depth tradeoff.
And it’s similar to something like a RightScale, and ideally will encourage them to let customers actually submit their own definition instead of the current clunky combo of ServerArrays and ServerTemplates (curl or Web console? Really? Why not a model like this?). RightScale must be in a tizzy right now, though really just integrating with this model should be easy enough.
Where To From Here?
As I alluded, we actually wrote our own tool like this internally called PIE that we’re looking to open source because we were feeling this whole problem space keenly. XML model of the whole system, Apache Zookeeper-based registry, kinda like CloudFormation and Azure. Does CloudFormation obsolete what we were doing? No – we built it because we wanted a model that could describe cloud systems on multiple clouds and even on premise systems. The Amazon model will only help you define Amazon bits, but if you are running cross-cloud or hybrid it is of limited value. And I’m sure model visualization tools will come, and a better registry/eventing system will come, but we’re way farther down that path at least at the moment. Also, the differentiation between “provisioning tools” that control and start systems like CloudFormation and bcfg2 and “configuration” tools that control and start software like Chef and Puppet (and some people even differentiate between those and “deploy” tools that control and start applications like Capistrano) is a false dichotomy. I’m all about the “toolchain” approach but at some point you need a toolbelt. This tool differentiation is one of the more harmful “Dev vs Ops” differentiations.
I hope that this move shows the value of system modeling and helps people understand we need an overarching model that can be used to define it all, not just “Amazon” vs “Azure” or “system packages” vs “developed applications” or “UNIX vs Windows…” True system automation will come from a UNIVERSAL model that can be used to reason about and program to your on premise systems, your Amazon systems, your Azure systems, your software, your apps, your data, your images and files…
You need to understand CloudFormation, because it is one of the most foundational changes that will have a lot of leverage that AWS has come out with in some time. I don’t bother to blog about most of the cool new AWS features, because they are cool and I enjoy them but this is part of a more revolutionary change in the way systems are managed, the whole DevOps thing.