DevOps and Continuous Delivery

If you want to go fast and have high quality, communication has to be instant, and you need to automate everything. Structure the organisation to make this possible, learn to use the tools to do the automation.

There’s a lot going on about DevOps and Continuous Delivery. Great buzzwords, and actually great concepts. But not altogether new. But for many organisations they’re an introduction to agile concepts, and sometimes that means some of the background that people have when arriving at these things in the natural way, through Agile process improvement, is missing. So what are we talking about?

DevOps: The combination of software developers and infrastructure engineers in the same team with shared responsibility for the delivered software

Continuous Delivery: The practice of being able to deliver software to (production) environments in a completely automated way. With VM technology this includes the roll-out of the environments.

Both of these are simply logical extensions of Agile and Lean software development practices. DevOps is one particular instance of the Agile multi-functional team. Continuous Delivery is the result of Agile’s practice of automating any repeating process, and in particular enabled by automated tests and continuous integration. And both of those underlying practices are the result of optimizing your process to take any delays out of it, a common Lean practice.

In Practice

DevOps is an organisational construct. The responsibility for deployment is integrated in the multi-functional agile team in the same way that requirement analysis, testing and coding were already part of that. This means an extension to the necessary skills in the teams. System Administrator skills, but also a fairly new set of skills for controlling the infrastructure as if it were code with versioning, testing, and continuous integration.

Continuous Delivery is a term for the whole of the process that a DevOps team performs. A Continuous Delivery (CD) process consists of developing software, automating testing, automating deployment, automating infrastructure deployment, and linking those elements so that a pipeline is created that automatically moves developed software through the normal DTAP stages.

So both of these concepts have practices and tools attached, which we’ll discuss in short.

Practices and Tools

DevOps

Let’s start with DevOps. There are many standard practices aimed at integrating skills and improving communication in a team. Agile development teams have been doing this for a while now, using:

  • Co-located team
  • Whole team (all necessary skills are available in the team)
  • Pairing
  • Working in short iterations
  • Shared (code, but also product) ownership
  • (Acceptance) Test Driven Development

DevOps teams need to do the same, including the operations skill set into the team.

One question that often comes up is: “Does the entire team need to suddenly have this skill?”. The answer to that is, of course, “No”. But in the same way that Agile teams have made testing a whole team effort, so operations becomes a whole team effort. The people in the team with deep skills in this area will work together with some of the other team members in the execution of tasks. Those other will learn something about this work, and become able to handle at least the simpler items independently. The ops person can learn how to better structure his scripts, enabling re-use, from developers. Or how to test and monitor the product better from testers.

An important thing to notice is that these tools we use to work well together as a team are cross-enforcing. They enforce each-other’s effectiveness. That means that it’s much harder to learn to be effective as a team if you only adopt one or two of these.

Continuous Delivery

Continuous Delivery is all about decreasing the feedback cycle of software development. And feedback comes from different places. Mostly testing and user feedback. Testing happens at different levels (unit, service, integration, acceptance, …) and on different environments (dev, test, acceptance, production). The main focus for CD is to get the feedback for each of those to come as fast as possible.

To do that, we need to have our tests run at every code-change, on every environment, as reliable and quickly as possible. And to do that, we need to be able to completely control deployment of and to those environments, automatically, and for the full software stack.

And to be able to to that, there are a number of tools available. Some have been around for a long time, while others are relatively new. Most especially the tools that are able to control full (virtualised) environments are still relatively fresh. Some of the testing tooling is not exactly new, but seems still fairly unknown in the industry.

What do we use that for?

You’re already familiar with Continuous Integration, so you know about checking in code to version control, about unit tests, about branching strategies (basically: try not to), about CI servers.

If you have a well constructed CI solution, it will include building the code, running unit tests, creating a deployment package, and deploying to a test environment. The deployment package will be usable on different environments, with configuration provided separately. You might use tools such the cargo plugin for deployment to test (and further?), and keep a versioned history of all your deployment artefacts in a repository.

So what is added to that when we talk about Continuous Delivery? First of all, there’s the process of automated promotion of code to subsequent environments: the deployment pipeline.

pipeline

This involves deciding which tests to run at what stage (based on dependency on environment, and runtime) to optimize a short feedback loop with as detailed a detection of errors as possible. It also requires decisions on which part of the pipeline to run fully automatic, and where to still assume human intervention is necessary.

Another thing that we are newly interested in for the DevOps/CD situation is infrastructure as code. This has been enabled by the emergence of virtualisation, and has become manageable with tools such as Puppet and Chef. These tools make the definition of an environment into code, including hardware specs, OS, installed software, networking, and deployment of our own artefacts. That means that a test environment can be a completely controlled systems, whether it is run on a developer’s laptop, or on a hosted server environment. And that kind of control removes many common error situations from the software delivery equation.

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