Recommandé
Contenu connexe
En vedette
En vedette (20)
Similaire à Agile Australia 2016 - Rescuing Legacy Software from Impending Doom
Similaire à Agile Australia 2016 - Rescuing Legacy Software from Impending Doom (20)
Dernier
Dernier (20)
Agile Australia 2016 - Rescuing Legacy Software from Impending Doom
- 1. RESCUING LEGACY SOFTWARE FROM IMPENDING DOOM martin.cronje@myob.com @martincronje jacques@nreality.com @jacdevos
- 3. Legacy code kills agility
- 5. Refactoring stories from the trenches
- 6. Why and when, but not how
- 7. Credits • Kent Beck on Small, Safe Steps and TDD • Robert C. Martin on Clean Code • Martin Fowler on Refactoring Techniques • Ward Cunningham on Technical Debt • Michael Feathers on Starting with a Mess • J.B. Rainsberger relating it to Accidental Complication
- 8. What is legacy code? What is the value in fixing legacy code? How do we speak to Product Owners about it? Should you rewrite? What is refactoring? When should we refactor?
- 9. What is legacy code?
- 10. Legacy code has a negative perception.
- 11. • Any code in production • Ancient code • Unsupported technology • Not up to standard • Code smells You may have heard…
- 12. - J.B. Rainsberger code that we feel afraid to Legacy code is valuable change.
- 14. Why fix legacy code?
- 15. • If it ain't broken, don't fix it • Make it easier to work with • For our future happiness • Good craftsmanship You may have heard…
- 16. Professionalism
- 17. Quality culture
- 19. Increasing the future value
- 20. …a trade-off against present value
- 21. In summary
- 22. Do POs understand the value in fixing legacy code?
- 23. • Not enough time • We cannot afford it • Business will close-down • Just one more feature • They allow us to recover You may have heard…
- 25. Do they really say that?
- 26. How do we explain it to them?
- 27. Risk to business continuity
- 29. In summary
- 31. • No. Rather the devil you know • No. It’s too expensive • Yes. Use latest technologies • Yes. Learnt from mistakes! You may have heard…
- 32. Big bang rewrite
- 34. Lesson #2: Puts your business at risk
- 35. Lesson #3: Always harder than you think
- 36. In summary
- 37. What is the alternative?
- 38. Refactoring is a safer bet
- 39. - Refactoring, Martin Fowler and cheaper to modify without …make it easier to understand behavior. changing its observable
- 40. Increase ease of change, while decreasing risk of change
- 41. Small incremental improvements into production
- 42. Cast safety nets as you progress
- 43. Start with lowest impact improvement
- 44. In summary
- 45. When do we refactor?
- 47. New code Code changes Solution wide TDD Refactoring Litter-Pickup Refactoring Comprehension Refactoring Preparatory Refactoring Planned Refactoring Long-Term Refactoring Refactoring workflows
- 48. Cleaning up as we go
- 49. Shanty Town campsite? What if this is the
- 52. In summary
- 53. Code that we’re afraid to change. Invest in making change easier and less risky. Talk to Product Owners about return on investment. Avoid rewrites, favour refactoring. Many, small improvements without changing behaviour. Keep it clean and escalate when crisis is imminent.
- 54. HOW ARE YOU GOING TO MAKE IT HAPPEN? martin.cronje@myob.com @martincronje jacques@nreality.com @jacdevos
Notes de l'éditeur
- Come and chat to us and let even code together We really what you to get some ideas on: how to make it happen!
- Beck, Kent (2003). Test-Driven Development by Example, Addison Wesley - Vaseem. Beck, Kent (2001). Extreme Programming Explained: Embrace Change 2nd. ed. Addison-Wesley. Fowler, Martin (1999). Refactoring: Improving the design of existing code. Addison Wesley. Feathers, Michael C (2004). Working Effectivelywith Legacy Code. Prentice Hall. Martin, Robert Cecil (2009). Clean code: a handbook of agile software craftsmanship. Upper Saddle River, NJ: Prentice Hall. Cunningham, Ward (2011). Ward Explains Debt Metaphor http://c2.com/cgi/wiki?WardExplainsDebtMetaphor Rainsberger, J.B. Fundamental Theorem of Agile Software Development https://vimeo.com/79106557
- To speaker: - Remember the trade-off between cleaning up and ROI - Let’s have a beer together
- Example: Spaghetti code that breaks all over the place when you make a change in one area Is very scary to change
- So, now that we know what legacy code is. Why would we bother to improve it?
- If it ain't broken, don't fix it But that approach, and not improving, got is into trouble the first place Make it easier to work with or even For our future happiness I think that is a great reason, but who would pay for your future happiness? Good craftsmanship That brings me to 3 main reasons we found To fix legacy code.
- We found that there are 3 main reasons To fix legacy code. The first reason is that: It is our PROFESSIONAL DUTY To TAKE GOOD CARE of our system This is almost like the Hippocratic Oath that doctors take “First do no harm … to code ” Following this oath, We always build well crafted software. Although professionalism is a great value , it has it’s limits: If we follow it blindly We might forget what we are paid for. We might starting building things that don’t benefit our customer.
- A second, related line of reasoning is that: our primary goal is to deliver a quality product to our customer. With this mindset, We will not compromise on quality And always go the extra mile to Although this is also a great mindset: it may cause over-engineering But over-engineering , by definition, does not add value in the customer’s terms.
- This brings us to the third and ultimate reason: The effort we expend on improving the system is an investment And this investment should have a value ….A monetary value In Dollars Reasoning in terms of investment is the only way to know how much fixing we should do. For example: Fixing an unimportant system that does not change all that often, will NOT pay off. But thinking in terms of investment is hard How do we actually go about determining the balance between: short term investments of adding NEW features and long term investments in making the system less expensive to work with
- Cost of delay Example: A special “Moonlight” project where a senior dev has to quickly hack in changes So get access to a new market Will slow us to a grind When that system starts getting used and need changes
- Cost of delay Example: A special “Moonlight” project where a senior dev has to quickly hack in changes So get access to a new market Will slow us to a grind When that system starts getting used and need changes
- They think refactoring fails? They think developers play? They don’t understand the impact of bad design?
- Example: I talked to some product owners and their response was: Nobody spoke to me about this, Nobody told me what the implication of this is, Nobody explained to me what was happening.
- Example: OneLaw document generation Example: If we work on a mission critical system, Like a trading system, And we know the system is messy – changing one part will impact other. Any change can easily make products stop working. Causing revenue and reputation damage. Even thought no related changes are made.
- HARDER AND HAEDER TO GET SOMETHING OUT Example: If we try to make a change to messy system, It might have adverse effects on other, unrelated parts, The time getting to grips with all the permutations, And making sure these permutations cause no harm, Is something that cannot be estimated, especially by an analyst.
- So, Now that we understand the problem and have time to fix it. What do we do? Why do we even bother with the crappy old system? Why don’t we just rewrite and start with a clean slate?
- No. Rather the devil you know: fine, but we have to do something, this devil is causing havoc No. It’s too expensive: yes, but development on the legacy system is also becoming increasingly expensive Yes. Use latest technologies + Learnt from mistakes!
- Thinking that: We learnt from mistakes in the old system. And we want to use the latest technologies anyway. This this line of reasoning is extremely tempting.
- But. Let me tell you about a project. I’m sure most of you know this story from your own experiences;) I joined a rewrite of a mission critical system 6 months after it began. …although it was supposed to be finished by the time I started. We were completely stuck! For months we were in a kind of “Whack a Mole” state, dealing with the one unexpected problem after the other. And despite the best effort of the analysts, The complexity of the old system Over years was completely underestimated, To make matters worse, the Maintenance team was churning out functionality on the old system. It was a nightmare trying to merge changes regularly from an incompatible system. This clearly taught me that: it is nearly impossible to predict the difficulty to rewrite an old complex system.
- We finally pushed through and released to production. But the week after release was one big crises: Parts of the system stopped working , for unexpected reasons. To make matters worse, Some business departments could not function at all, Since they started to rely on idiosyncrasies of the old system. I remember getting a call from one department manager. He shouted in my ear that: Our mess will get him fired! and he is only weeks from retirement! The lesson I got from this was that: rewrites can bring a business to its knees They are extremely risky. Especially on mission critical systems.
- We finally pushed through and released. But the week after release was one big crises: Parts of the system stopped working , for unexpected reasons. Further, Some business departments could not function at all, Since they started to rely on idiosyncrasies of the old system. I remember getting a call from one department manager. He shouted in my ear that: Our mess will get him fired! and he is only weeks from retirement! This taught me that: rewrites can bring a business to its knees They are extremely risky.
- We should think twice before we rewrite a system. And resist the fallacy that “we will do it better this time round”
- But we still need to do something about our legacy.
- This makes it pretty clear that: Refactoring the current system is often a safer bet than a rewrite. But what is this thing we call refactoring? The word “Refactoring” does not even appear in the English dictionary!?
- Simply put, refactoring: Is a disciplined, step by step process That gradually improves The internal quality Of our system Refactoring is never a quick fix. Refactoring does not change behavior: That includes things like bug fixes and performance improvements.
- And when we refactor We have 2 goals: Firstly, we want to make it easier to change the system. In other words, we want to make it less expensive to get new valuable features out the door. Secondly, we want to reduce the risk in making changes to the system. We want to get to the point Where we can deploy changes regularly without loosing sleep over it. Reducing the risk of change is especially relevant to mission critical legacy systems
- Refactoring achieves these goals, Through a process of, Divide and Conquer: We want to: make many, small seemingly insignificant Improvements to the system. We want to avoid big, commits like the pest. Since big changes are inherently risky. In the words of Kent Beck We must get into the habit of: Taking “Small, Safe steps” Following this approach, we can make HUGE improvements in a much safer way.
- The next thing to remember is that Refactoring puts Safety First. This is done by Capturing the current behavior of the system with tests. And you want to run these tests on every change. TO get quick feedback. If you have broken a major feature. (even thought this is not bullet proof) A lot is written on the topic of testing, but that is outside the scope of this talk. I recommend Michael Feather’s “Working effectively with legacy code” is a good start
- Lastly, we have to realize with refactoring, Is that there are usually many things you can do To improve the the code base Without rocking the boat So we find that a good rule of thumb is to: start with the lowest risk readability improvements. Like the naming standard Refactoring legacy code is a process of managing risk in changes. Starting with the lowest risk improvements. will make the rest of the refactoring process much easier. But Martin will talk more about When we refactor.
- In summary, refactoring is a process that makes change less risky and expensive By making many, small, safe improvements To the internal structure of your code
- For example: Fixing a bug: is a behavior change Fixing performance: is a behavior change Splitting the system into separate services: a refactoring change.
- TDD Refactoring Litter-Pickup Refactoring Comprehension Refactoring Preparatory Refactoring Planned Refactoring Long-Term Refactoring
- Example: when making a change in someone else’s code: break long method into clearly named sub-methods, to make it clear to others what you figured out
- Example: we can see that spaghetti-code in our trading system is fragile and dependent. If we change things in one part we can see that the system will keep crashing down in other important areas. We need to create awareness that modules need to be broken up, into subsystems.
- Example: We are in a dangerous minefield of important code, trying to figure out how current code works, and where we want to take it. use a detached head, to start making throwaway changes for the purpose of learning. once we learnt, we start with a clean checkout, knowing where we will go.
- In this talk we saw that: Legacy is code that we’re afraid to change And that we should invest in making it easier and less risky to work with. --- We should also clearly communicate to our PO What the impact of legacy is and the value in improving it. --- We saw the dangers of rewrites and the benefits of refactoring, in terms of risk and cost. And we saw that refactoring avoids risk by making lots of little improvements, Without changing any observable behavior. --- Finally, We should always quietly improve our system, but that should make it clearly heard when there are big underlying problems To speaker: - Remember the trade-off between cleaning up and ROI - Let’s have a beer together