Containers are the third model of compute, after bare metal and virtual machines – and containers are here to stay. Docker gives you a simple platform for running apps in containers, old and new apps on Windows and Linux, and that simplicity is a powerful enabler for all aspects of modern IT.

In this article I’ll walk through the major use-cases where people are using containers today, I’ll show why Docker is a safe technology choice to invest in, and I’ll finish with a learning path for you to get started with containers.

Use Case #1: Cloud Migration

Every company has a view on moving apps to the cloud. From five-year migration programs, to an immediate need to migrate because the data centre provider is shutting down in three months (this really does happen). Whatever the driver, running in the cloud should bring agility, flexibility and cost savings. To get there you used to have to choose between two approaches: Infrastructure-as-a-Service (IaaS), and Platform-as-a-Service (PaaS).

IaaS means renting virtual machines and deploying your apps in the same way you do in the datacenter. You can use your existing deployment steps, but you take all the inefficiencies of running virtual machines on-prem into the cloud. Take a simple example of three distributed apps, where each component runs in a separate VM for isolation:

Running those apps to the cloud might use 30 VMs in production, for high availability and scale. That can cost $5K a month. You’ll still have single-digit CPU utilization for your money, and you can’t dynamically scale because of the time it takes to start and configure new VMs.

PaaS is at the other end of the scale. It means using the full product suite of your cloud provider and matching the products to the features your app needs. In Azure that could mean using App Services, API Management, SQL Azure and Service Bus queues.

You get complete managed solutions from the PaaS option, together with high-value features like auto-scaling. And using shared services means you should save on cost – but it’s going to take a project for every app you want to migrate. For each app you’ll need to design a new architecture, and if you’re swapping out core components you’re going to need to change code.

Docker gives you a new option which combines the best of IaaS and PaaS – move your apps to containers first, and then run your containers in the cloud. It’s a much simpler option that uses your existing deployment artifacts without changing code, and it gives you high agility, low cost and the flexibility to run the same apps in a hybrid cloud or multi-cloud scenario:

The process is simple. For each component in your app you write a Dockerfile, which is a script that deploys the component into a Docker image. Docker images are a snapshot of one version of your component – they contain the compiled binaries, dependencies and configuration – everything your app needs to run. The image is portable, you share it by pushing it to a central registry of images, which could be the public Docker Hub or your own private registry.

Then you run your app in a container and it runs in the same way everywhere.

Use Case #2: Cloud-Native Apps

Cloud-native applications are how greenfield apps should be built. The Cloud Native Computing Foundation definition is container packaged, dynamically managed, microservice apps. In a cloud-native architecture, each component runs in its own service, with its own private data store. The microservices-demo application on GitHub is a great sample architecture:

It’s a web app with a single front-end, but the full feature set is provided by many small services – like the catalogue service, cart service and payment service. Those services each run in their own containers. Logically they form one app, but they’re physically distinct components and that means they can all have their own deployment cadence. You can add catalogue features by deploying an updated catalogue service, without changing any of the rest of the app.

This is a huge enabler for the business because it removes lengthy regression-test cycles and decreases the time from idea to deployment. There’s no need to test the cart service or the orders service if you’re adding a catalogue feature, because those other components stay the same. It’s also a great technology enabler. The sample project uses .NET Core, Go, NodeJS, Java, Mongo and MySQL – a whole range of technologies. The architecture gives you the freedom to use the right technology for each component.

You can also include production-grade open source components into your solution. Popular technologies are already packaged into public Docker images which are owned by the OSS project team, so you get the best-practice configuration of the latest version of the software, just by running a container. Check out the Cloud-Native Computing Foundation’s landscape, which categorizes a huge range of technologies that fit neatly into cloud-native apps, from message queues and databases to metrics servers and dashboard visualizers.

Adopting cloud-native design accelerates your app delivery and the end result is a self-healing application which is cleanly defined in a single manifest file, and which you can deploy to any Docker cluster, knowing it will work in the same way everywhere.

Use Case #3: Modernizing Traditional Apps

Cloud-native apps should be an important part of your future projects, but enterprises already have a much larger landscape of traditional applications. These are apps with a large monolithic codebase, running as single components. They may have manual deployment processes, or they may be automated by joining many tools. They are complex and time-consuming to develop and test, and fragile to deploy.

Many organizations are also managing apps across a range of operating systems which are at or nearing end-of-life – including Windows Server 2003 and 2008. It’s hard to maintain an application landscape which is running on diverse operating systems, which each have different toolsets and different capacities for automation.

Docker brings consistency to all containerized applications, old and new, on Windows and Linux. The Windows Server Core Docker image is maintained by Microsoft and it has support for older application platforms – including .NET 2.0 and 32-bit apps. You can take a 15-year old application and run it in a Windows container, deploying your existing MSIs in the Dockerfile, with no code changes.

You can run your monolith in a container and get all the efficiency, portability and security benefits of Docker. Old apps which are still being used but not actively developed can stay as monoliths. Apps which are still active projects can make use of Docker to modernize the application architecture. You can split features out of the monolith, add new features and use functionality from open source components, all running in containers and all managed by Docker:

Containers let you evolve your traditional apps towards a cloud-native design, without needing a 2-year project to rearchitect them as microservices. You can run a production Docker cluster which has a mixture of Windows and Linux nodes, for running cross-platform distributed applications. You could run Nginx in Linux containers to add performance, security and scalability to an ASP.NET WebForms app running in Windows containers.

Use Case #4: Technology Innovation

Technical innovation doesn’t end with cloud-native apps. Trends like IoT, machine learning and serverless functions are all coming closer to mainstream, and they’re all made easier and more manageable by Docker. I’ll focus on serverless here.

Serverless is all about containers. Developers write code and the serverless framework takes care of packaging the code into a Docker image, and running it in a container when a trigger comes in – like an HTTP request or a message on a queue. The Cloud Native Computing Foundation has specced out the architecture and deployment pipelines which are common to all serverless platforms:

Serverless started with AWS Lambda and Azure Functions, but it isn’t just for the cloud. There are great open-source projects that use the same architecture and pipeline, but they run in Docker, so you get all the benefits of a consistent platform on the developer laptop, on test VMs in the datacenter, and on any cloud.

Open-source platforms like OpenWhisk, Nuclio, Fn and OpenFaas are powered by containers and have very active communities, as well as support from enterprises like IBM and Oracle. And because they’re just containers, you can run a serverless platforms on the same Docker cluster that’s already running your cloud-native apps and your traditional apps.

Use Case #5: Process Innovation & DevOps

The last big challenge facing enterprise IT is about cultural change and the move to DevOps, which should bring faster releases of higher quality software. DevOps is rightly positioned as people and process change, using frameworks like CALMS which focuses the change on Culture, Automation, Lean, Metrics and Sharing.

But it’s hard to make big changes and measure their impact unless you underpin them with new technologies. Creating a folder called “DevOps” on the shared drive and putting all your deployment documents in there is not progress. Moving to Docker helps drive the change to DevOps, underpinning all the elements of CALMS:

The most significant benefit is helping the cultural change. Having teams working on the same technology and speaking the same language – Dockerfiles and Docker Compose files – is a great way to break down barriers. And people are excited by Docker. It’s an interesting, powerful new technology which is easy to get started with and quickly improves practices from development to production. Teams adopting Docker are enthusiastic and that helps drive big changes like the move to DevOps.

Containers: Flexible and Open Technologies

Moving the to the cloud, delivering new apps, modernizing old apps, supporting technology innovation and process innovation – that’s pretty much everything that’s happening in the IT industry. Docker helps it all happen, which is why containers will take over the world.

But there is some work to do to get there. You need to write Dockerfiles to package your apps to run in Docker containers. You need to write Docker Compose files or Kubernetes manifests to define all the pieces that make up a distributed, containerized app. Deploying, managing and monitoring apps is different when they’re running across hundreds of containers.

You need to make an investment to get the benefit of containers, but it’s a safe investment to make. You can start with what you currently have, and you’ll be moving to open technologies. You’re not restricted to certain languages or frameworks – you can Dockerize pretty much anything if you can script the deployment. And you won’t be locked in to any one vendor – the Docker image format and the container runtime spec are open standards, so you can run your apps on any container platform.

The Learning Path: Getting Started with Docker

If containers are going to going to take over the world, you’d better get on board. As soon as you start looking at the container space you’ll see a huge array of technologies – Docker Swarm, Kubernetes, containerd, Istio, as well as all the vendor platforms – Docker Enterprise, AKS on Azure, and Amazon’s EKS. Where do you start?

Here’s my opinionated learning path. It starts you off easily and adds capabilities (and complexity) with each step. The idea is you stop when you get what you need. The endgame could be running a cloud-native .NET Core app on a service mesh with Istio on Kubernetes, or it could be running .NET Framework apps in Windows containers on Docker Swarm. Either of those is correct, if it works for you:

There you are. It’s simple really, and Pluralsight is your friend here, there’s a whole set of Docker and Kubernetes courses, with lots more on the way. Now is the time to get started, so install Docker Desktop on Mac or Windows and go Dockerize!

This article is part of XPRT. magazine #7.
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