This is a question I hear a lot, people have heard of (or may follow) Scrum and often have read about DevOps. They want to know whether DevOps is a replacement for Scrum or if it’s something they should be doing as well. Others believe that Scrum and DevOps are incompatible, in this post I want to talk about what both of these are how (because spoilers – they can) they should be used together.
What Is Scrum?
Lets start with the obvious question, if we’re going to discuss how DevOps and Scrum interact we need to define what exactly what we mean.
Quoting from The Scrum Guide:
Scrum is a lightweight framework that helps people, teams and organizations generate value through adaptive solutions for complex problems.The Scrum Guide
The Scrum Guide is an extremely concise and valuable guide to Scrum. If you haven’t read it I strongly recommend you do. However, for the purpose of this post I’m going to to highlight a few points.
Scrum employs an iterative, incremental approach to optimize predictability and to control risk.
An Increment is a concrete stepping stone toward the Product Goal. Each Increment is additive to all prior Increments and thoroughly verified, ensuring that all Increments work together. In order to provide value, the Increment must be usable.
The Definition of Done is a formal description of the state of the Increment when it meets the quality measures required for the product.Various Sections of The Scrum Guide 2020
When many people think of Scrum they discuss the Scrum Events, these include Sprints, Retros, Planning Sessions, and Sprint Reviews. However, equal importance should be given to the underlying theory of empiricism and incremental nature.
Each Scrum Team should deliver at least one increment of work each Sprint, this increment should be potentially releasable, and meet the Definition of Done. They will then meet in a Sprint Review meeting and discuss what they should do next to deliver maximum value.
What Is DevOps?
DevOps is, at it’s core an effort to reduce the divide between development and operational teams. Literally, Dev-Ops there are many practices and ways of doing this from the cultural to the technological however what has most likely led you to this post are the ideas of Continuous Integration, Continuous Delivery, and Continuous Deployment. Again, DevOps has many valuable lessons, I’m focusing on these three not to devalue the other concepts, but simply because they are some of the key concepts we need to understand for this article.
- Continuous Integration requires that each developer merges their code into the master branch every day and if the master build breaks it is resolved or rolled back within ten minutes.
- Continuous Delivery is a promise that any code which is the master branch is always in a potentially deployable state. Untested and unverified code is never merged in.
- Continuous Deployment is an automation mechanism which pushes whatever is in the master branch into environments (often production) without any manual steps.
As you can see these are cumulative, so teams may practice Continuous Integration but may not practice Continuous Delivery or Continuous Deployment. It is also nearly impossible to practice Continuous Deployment unless you also follow Continuous Delivery and Continuous Integration.
It’s also worth mentioning the “3 Ways of DevOps” these were popularised by the highly successful book The Phoenix Project. The 3 Ways are:
- Flow/Systems Thinking
- Amplify Feedback Loops
- Culture of Continual Experimentation and Learning
Using Scrum and DevOps Together
Now that we’ve talked about what Scrum and DevOps are (or at least highlighted some of the relevant and key parts of each) I want to discuss whether these concepts can work in harmony together.
The first aspect to address is the Scrum concept of an increment. The Scrum Guide says that each team should produce at least one increment of “Done” software which is potentially releasable to production each sprint. I believe that the three concepts of Continuous Integration, Continuous Delivery, and Continuous Deployment are not only compatible, they are the natural evolution of this requirement.
If an engineering team is following CI, CD, and the other CD then each day (or less) a piece of work should be added to master. This means that a typical team of 7 engineers working a standard two week sprint could easily produce seventy or more increments in a single sprint. They key here is that by breaking down the Scrum Product Backlog Items down into single pieces of work which can be individually developed with a single day and then tested in isolation. This is not easy, however with practice and strong story splitting skills it can be done.
It’s also worth mentioning the Definition of Done. The Scrum Guide states that each increment must meet the Defintion of Done. Continuous Delivery states that the master branch should be always be in a deployable state. What a high performing Scrum/DevOps team should do is write automated tests which execute against incoming pull requests into their master branch to confirm that it always meets the agreed Definition of Done. This not only reduces the amount of repetitive testing work expected of the team but it highlights immediately when a proposed increment does not meet the team’s Definition of Done. If it doesn’t, it’s not merged in.
Before wrapping up I also want to consider the 3 Ways of DevOps I discussed above.
By building the Definition of Done into the Deployment Pipeline of the product we support the 1st Way by ensuring that the requirements of the team are baked into the pipeline.
The 2nd Way is to shorten feedback loops. Scrum emphasises the value of engaging with stakeholders frequently to ensure that they are involved and know the current state of the product. Scrum is also based on empirism, the belief that only we can only make estimates by looking at real data, by valuing the 2nd Way and shortening those feedback loops wherever possible this gives us a more accurate picture of what impact our changes have had. Simply put, this more accurate view provides the transparency we need to inspect and adapt. These are the three pillars of empirism.
Scrum also defines an event, the Retrospective where team members should meet to discuss ways to improve the quality and effectiveness of the team. This fosters the experimentation and innovation expected of the 3rd Way. These ideas aren’t working against each other. Scrum is providing events to ensure that the DevOps approaches are being honoured.
DevOps is often seen as a Scrum upgrade or perhaps a replacement to the agile framework. However it shouldn’t be. I believe that many of the automation and development strategies of DevOps are the natural evolution of Scrum principles and fit very neatly into any team already using the process.
With automated tests continuously testing each increment to guarantee that it meets the team’s Definition of Done increments can become smaller and a continuous flow of high value work can be delivered with shorter lead times and higher quality.