Streamed Lines at 11

As I was starting to prepare for a class I'm giving at the Software Test and Performance conference in Cambridge MA this October I looked over a paper Brad Appleton and I wrote in 1998 on branching patterns: Streamed Lines, and I started to think about the path from this paper to the SCM Patterns book. Streamed Lines describes a number of branching patterns and when it's appropriate to use each one. From time to time people still tell me or Brad that this is one of the better overviews of branching strategies they have seen.

The paper grew out of material we gathered in a workshop at ChiliPLoP 1998 in Wickenberg AZ. We organized the set of index cards, categorized by color-coded stickers into the paper we prepared for workshopping at PLoP 98 (which was the PLoP conference I was program chair for). Many steps later, with encouragement from John Vlissides, we submitted a book proposal and started working on Software Configuration Management Patterns. The SCM Patterns book says a lot less about branching than Streamed Lines, and more about how SCM and version management practices fit into a pragmatic and agile development environment. Given how the book morphed from the original branching patterns, there is still a place for the information in Streamed Lines.

Streamed Lines may be due for an update to take into account how things like distributed version management systems like git and Mercurial affect the cost of branching. Regardless of tools, branching can have costs relative to not-branching; just because something is easy to do, does not mean that it's the right thing to do, but newer tooling is worth considering as you develop an SCM strategy.

Have you read Streamed Lines? Does it need an update? What would you change about it? How much should tools affect the principles it describes?

Sprint Review as Agile Enabler

An agile process such as Scrum is built on a number of both project management and engineering practices. The engineering practices support the project management practices and the project practices guide engineering decisions. While it takes more than the presence (or absence) of any one practice to cause your agile project to succeed or fail, some practices can drive your process in a powerful way. Sprint reviews are one practice that, when done with the right attitude, can help teams develop and maintain a good project rhythm.

An iteration process has mechanisms in place to help steer teams. Of all of the practices that support iteration, regular sprint reviews help teams and product owners get the feedback that they need to improve their performance. Reviews are also one practice that I've noticed that teams slack off on, especially when they are first starting out.

A common rationale for not having an iteration review are that there isn't enough to show. When the team is not making progress is the most important time to review progress with the product owner and evaluate how the project is doing and what needs to change. While the first review may be difficult, if everyone on the team is committed to a successful project, a review of less than successful sprint can have many positive consequences:

• The product owner many be more impressed my the progress than the team thought, freeing the team to take more ownership of their work.
  
• The product owner may be better able to understand that the backlog might be the wrong size as the team compares the results of sprint to the backlog, providing the team with the data it needs to have a more attainable backlog.
• The team may recognize things it can do to work more effectively.
  

It's important that everyone understand the reviews for what they are: brief, lightweight mechanisms for evaluating progress as a group and and understanding how to do improve. This means that it's OK for things to go wrong in a review. And the team should not spend a lot of time preparing or setting up environments. (With good engineering practices you should be able to build and deploy a "review version" quickly. If you can't considering prioritizing Deploying Early.)

As you identify issues it's also important to review progress on these issues at subsequent reviews. If you let them drop then the people at the review will come to understand that the review feedback is part of an empty exercise. It's OK to acknowledge that a review item wasn't acted upon, or is no longer necessary. But you should discuss each action from a review at the next one.

While this sounds easy, there are some challenges including establishing trust between the product owner and the team, and developing an understanding that they share the same goals. You need to be able to talk about what's not working, and figure out how to make it work, not just assign blame. If the team and the product owner is new to Scrum, and the project is new, you may have to start with a premise of trust. This is hard, but with the regular feedback of a review each sprint, the stakeholders will be able to readily evaluate everyone's dedication to the project.

It's very important to discuss what went well, preferably before covering what needs to be improved. (I tend to favor the attitude I learned from patterns writers workshops.)

Some suggestions for those struggling with agile:

• Have reviews at the end of each Sprint, using your backlog as an agenda.
• Show the work done in the simplest way possible.
• Collect feedback both on the work and the process, and identify things that went well and things to improve.
  
• Save the list of things to improve for the next review, and be sure to discuss them.
  

Agile methods are based on periodic feedback, and a review is a lightweight process to give feedback essential to a team. If your team is struggling with agile, have reviews each sprint, and try to understand what's working and what's not. The review will guide you to the most critical issues (technical and organizational) that you need to address.

Releasing, Branches, and Agile Teams

When Brad Appleton and I wrote the SCM Patterns book we discussed two branching patterns related to releasing software: Release Line and Release Prep Codeline. The first, is a pattern that allows teams to easily support released code. The second is a pattern to help you "stabilize" a codeline before a release while allowing parallel work for the next release to proceed. Too often teams start Release Prep Codelines at the wrong time or for the wrong reasons, without understanding the costs . Given the rate at which changes happen on agile codelines, the costs of creating a branch can be large if do it for the wrong reasons.

If an ideal agile team had "shippable" software at the end of every iteration, a Release-Prep codeline isn't necessary. You just label your code at the end of the final sprint, and if you need to provide a fix that can't be done from the mainline code, you start a release branch from that label.

Many teams can't ship at the end of every sprint, creating a Release Prep Codeline (branch) is a useful: it avoid some poor alternatives, like having a code freeze. The branch can receive small changes to fix problems, and the mainline can add new features, refactor, and integrate the fixes from the release-prep branch.

As the time between when the branch is created and the project is released grows, the cost of merging changes between the branch and the Mainline increases because the source code diverges. This decreases the velocity of the team and can make the time to release grow more.
A long interval between branching and release often happens for reasons like:

• Quality issues. There are a lot of problems, so going from "feature complete" to "shippable" takes longer than expected.
• "Code Freeze" happens before "Feature Freeze." Not explicitly, but after the branch is created you identify new "must-have" features. This gets worse as the time between branch and ship increases.

So what is a team to do? Here are some suggestions:

• Be agile and prioritize: If the release is the most important task, do that work on the mainline, and have everyone work on it. Don't branch until you are ready to ship.
  
• Add automated tests early. Try to be "ready to ship at the end of the sprint," so you can avoid the costs of branching.
  
• Don't branch until you really are feature complete, and use the Release-Prep Branch only for a constrained set of fixes.

If you really need to start future work before the current release is ready to ship consider either:

• Doing all work on the main line and isolate "future work" by architectural techniques. (Make new features plugins, for example).
  
• Keeping the work that is highest priority on the main line, and create a Task Branch for the future activity. Those on the task branch are responsible for merging main line code into their branch, and when the release is done, the task branch get copied to the main line.

My tendency is to want to keep the highest priority work on the main line as long as possible. Usually the code you are about to release meets this criterion.

Technically, these are simple technical approaches to implement. Like all SCM issue, there a are many non-technical issues to address. Product owners need to understand the costs of "working in parallel" and an agile team is responsible for making sure that the product owners know these costs so that they can make the correct decisions about when to start a parallel work effort.

How has your team addressed pre-release and release branches? If you read this and have an opinion, please comment!