There are five principles at the heart of continuous delivery:

  • Build quality in
  • Work in small batches
  • Computers perform repetitive tasks, people solve problems
  • Relentlessly pursue continuous improvement
  • Everyone is responsible

It’s easy to get bogged down in the details of implementing continuous delivery—tools, architecture, practices, politics—if you find yourself lost, try revisiting these principles and you may find it helps you refocus on what’s important.

Build Quality In

W. Edwards Deming, a key figure in the history of the Lean movement, offered 14 key principles for management. Principle three states, “Cease dependence on inspection to achieve quality. Eliminate the need for inspection on a mass basis by building quality into the product in the first place.”

It’s much cheaper to fix problems and defects if we find them immediately—ideally before they are ever checked into version control, by running automated tests locally. Finding defects downstream through inspection (such as manual testing) is time-consuming, requiring significant triage. Then we must fix the defect, trying to recall what we were thinking when we introduced the problem days or perhaps even weeks ago.

Creating and evolving feedback loops to detect problems as early as possible is essential and never-ending work in continuous delivery. If we find a problem in our exploratory testing, we must not only fix it, but then ask: How could we have caught the problem with an automated acceptance test? When an acceptance test fails, we should ask: Could we have written a unit test to catch this problem?

Work in Small Batches

In traditional phased approaches to software development, handoffs from dev to test or test to IT operations consist of whole releases: months worth of work by teams consisting of tens or hundreds of people.

In continuous delivery, we take the opposite approach, and try and get every change in version control as far towards release as we can, getting comprehensive feedback as rapidly as possible.

Working in small batches has many benefits. It reduces the time it takes to get feedback on our work, makes it easier to triage and remediate problems, increases efficiency and motivation, and prevents us from succumbing to the sunk cost fallacy.

The reason we work in large batches is because of the large fixed cost of handing off changes. A key goal of continuous delivery is to change the economics of the software delivery process to make it economically viable to work in small batches so we can obtain the many benefits of this approach.

Computers Perform Repetitive Tasks, People Solve Problems

One of the earliest philosophical ideas of the Toyota tradition is jidoka, sometimes translated as “automation with a human touch.” The goal is for computers to perform simple, repetitive tasks, such as regression testing, so that humans can focus on problem-solving. Thus computers and people complement each other.

Many people worry that automation will put them out of a job. This is not the goal. There will never be a shortage of work in a successful company. Rather, people are freed up from mindless drudge-work to focus on higher value activities. This also has the benefit of improving quality, since humans are at their most error-prone when performing mindless tasks.

Relentlessly Pursue Continuous Improvement

Continuous improvement, or kaizen in Japanese, is another key idea from the Lean movement. Taiichi Ohno, a key figure in the history of the Toyota company, once said,

Kaizen opportunitites are infinite. Don’t think you have made things better than before and be at ease… This would be like the student who becomes proud because they bested their master two times out of three in fencing. Once you pick up the sprouts of kaizen ideas, it is important to have the attitude in our daily work that just underneath one kaizen idea is yet another one.

Don’t treat transformation as a project to be embarked on and then completed so we can return to business as usual. The best organizations are those where everybody treats improvement work as an essential part of their daily work, and where nobody is satisfied with the status quo.

Everyone is Responsible

In high performing organizations, nothing is “somebody else’s problem.” Developers are responsible for the quality and stability of the software they build. Operations teams are responsible for helping developers build quality in. Everyone works together to achieve the organizational level goals, rather than optimizing for what’s best for their team or department.

When people make local optimizations that reduce the overall performance of the organization, it’s often due to systemic problems such as poor management systems such as annual budgeting cycles, or incentives that reward the wrong behaviors. A classic example is rewarding developers for increasing their velocity or writing more code, and rewarding testers based on the number of bugs they find.

Most people want to do the right thing, but they will adapt their behaviour based on how they are rewarded. Therefore, it is very important to create fast feedback loops from the things that really matter: how customers react to what we build for them, and the impact on our organization.