This afternoon, I sat in a Keynote by Bob McWhirter at TSSJS 2010. Bob is the Chief Architect of Cloud Computing at Red Hat. Bob is "The Despot" at Codehaus, helped start Groovy and founded Drools. Below are my notes from his talk.
So what is the cloud?
It's the next logical step in application delivery.
How did we get to the cloud? First, we jammed a lot of servers into a closet (back in the .com days). That's a lot of stuff to deal with if all you want to do is deliver an internet-based service. Then we did some colo. The problem with colo was that it was still our stuff. Then we leased managed servers. With the cloud, we lease what appears to be servers (or services). This is a path we've all been taking to abstract the annoying bits away from hosting an internet-based service.
The typical diagram of a cloud has IaaS, PaaS and PaaS. IaaS abstracts away hardware. PaaS abstracts away services. SaaS abstracts away software.
Tenants of the cloud:
- The illusion of infinite resources.
- On-demand acquisition and provision.
- Someone else's responsibility.
Magicians provide the illusion of pulling a card out of your ear, but they don't actually do it. Because there are limits of what we can do. With on-demand requisitioning, there's no more purchase orders. There's no more waiting for delivery. No waiting for IT to rack it. Or install it. By having someone else manage your hardware, it's not your problem. There's clear lines of responsibility. This intentionally limits visibility into the implementation. Hopefully it's best-of-breed.
The Cloud is really just a mindset. Virtualization makes it affordable to make mistakes. Repeatedly. Each service is managed as an autonomous entity. Services are designed for scalability.
Architecture 101 give us a presentation layer, a business logic layer and a persistence layer. You can scale it by putting many instances on many servers. However, the truth is that most apps are a big ball of mud. You need to get your application in order, then figure out which parts really needs to scale. Is the web tier really where we have trouble? Painting HTML isn't all that hard.
You don't have to put everything in the cloud. The cloud is not a revolution. We still need containers for web things, messaging things, storage of things and other things. Containers still exist, they're just in the cloud.
From container to cloud
When you have an application and a database, there's not much to abstract away into the cloud. However, as soon as you notice your DB is slow, you'll add caching. Once you hit your machine's memory limit, you discover distributed caching systems. Once you've done this, you'll discover that the network isn't all that slow, especially compared to spinning disks. Then you realize that you don't even need the storage and you can keep everything in cache. From there, you move to a RESTful caching service. Then you call it a NoSQL Service so you can be buzzword-compliant.
As far as caching services, there's many available, but a lot of them are startups. However, the cloud does not have to mean external 3rd-party providers. Remember DBAs? It was their job to view the database as a service and to protect it. There's a good chance that we'll end up with DBAs for services. By turning caching into an independent service, it becomes subject to economies of scale.
The cloud is a mindset. It's an SOA approach that allows groups to specialize and optimize for scale.
So how do you implementing a local cloud? We already have great caching technologies. Bob, with his JBoss hat on, recommends Infinispan and its REST API. To get around network latency, you can still run your cloud on your LAN. You're essentially trading disk traffic for network traffic. You can use many hands (e.g. MapReduce) to make things happen quickly.
Besides caching, there's a number of other services that can be put in the cloud. For example:
- Messaging (REST-MQ
- Security & Identity (OASIS, etc)
- Computation (query & otherwise)
- Transactions (REST-TX)
- Business Process Management
- Telephony (VOIP, SMS)
Your application becomes a stack of services, instead of a stack of software.
Higher-order business-logic services are also subject to cloudification. Ultimately, going into the cloud is not rocket science. The cloud does not turn everything on its head. We don't have to wait for new companies to develop new technologies. Startups may be the best consumers of the cloud, but might not be the best providers. We'll let the startups assume the risks for now. Until the 3rd party services have been proven, it's probably best to build your own cloud of services.
More than anything, the cloud has caused a return to fundamentals. Once your app is a collection of services, you can easily pick and choose what pieces you want to put in the cloud. This is where we're headed, whether you like it or not. As more apps become global-scape, you're going to run into these issues. By adopting a cloud mindset and architecture, your app can be prepared for scalability issues.