Front Trends: Migrating complex software

A talk about migrating complex software, based on my experience of Angular => React at Songkick.

1. ! From Angular to React @Jack_Franklin
2. Migrating complex so!ware
8. The Store
9. Started 2 years ago, built on Angular 1 Tickets being sold constantly Used by our flagship clients
10. The store works well. But changing it is very tricky.
11. Legacy codebase An old version of Angular 1 Feature bloat Original developers have gone
12. We can't iterate quickly, respond to bug reports, or build new features in a timely manner. We lack confidence in our system.
13. The Four T's — Tech — Tests — Team — Talking
14. Tech
16. Big bang vs incremental
21. Bit by bit ! Release early and often, one bit by a time Learn as we migrate and get better at it Don't break any existing functionality
22. https://www.martinfowler.com/bliki/ StranglerApplication.html
23. http://2017.theleaddeveloper.com/ | @saleandro
24. We shipped migrated code the day a!er starting this migration.
25. The Theory Components (or directives in Angular)
30. The plan
33. Migrating a component
34. 1. Find all dependencies that a directive uses
35. 2. Migrate all of those one by one to React
36. 3. Write the React component import React, { Component } from 'react' class ListingsButton extends Component { // code left out to save space :) render() { return ( <a href="" className="">Buy now!</a> ) } }
37. But how do we embed this within Angular? Angular directives are used as if they were custom HTML elements: <li> <h2>Rihanna at The O2</h2> <listings-button url="...">Buy now</listings-button> </li>
39. With ngReact <li> <h2>Rihanna at The O2</h2> <react-component name="ListingsButton" props="..." /> </li>
40. We can continue this strategy, migrating the other components to React: <li> <react-component name="ListingsTitle" props="..." /> <react-component name="ListingsButton" props="..." /> </li>
42. And now we can migrate this into one big React component! import React, { Component } from 'react' import ListingsTitle from './listings-title' import ListingsButton from './listings-button' class ListingsItem extends Component { render() { return ( <li> <ListingsTitle ... /> <ListingsButton ... /> </li> ) } }
43. And update our template <react-component name="ListingsItem" props="..." />
45. And we now rinse and repeat as we replace Angular with React Forever.
46. Tests
47. We cannot break the store
48. Unit tests Migrated from Angular to React + added to as appropriate.
49. https://www.sitepoint.com/test-react-components-jest/
50. Unit tests are coupled to the implementation code.
51. Acceptance tests
53. Automated tests that are entirely decoupled to the application code.
54. Because they are slow to run, we keep acceptance tests to our core user journeys
55. We also run our acceptance tests in IE11 to catch any IE bugs. Soon we hope to run them across all browsers we support, both desktop & mobile
56. Team
57. Keeping people happy and productive We knew this migration was going to be at least 6 months, more likely closer to a year. 1 1 It's been 9 months so far...
58. Momentum & Prioritisation
59. One of the goals of this migration is to make it easier to fix bugs with confidence.
60. Pick work based on bugs and churn rate, not code quality
64. Mix larger, multi-week work with short, 1-2 day work, to keep momentum.
66. Break down large work into smaller cards and pull requests
67. Feature branches
70. Release early, release o!en Encourages small pull requests and units of work
71. Release early, release o!en Keeps momentum up in the team and keeps risk to a minimum
72. Release early, release o!en ! Easier to react 2 to a bug if release causes it 2 pun very much intended
73. The scout's rule Always leave things better than when you found them.
74. A migrated codebase is not a perfect code base
75. The next time you touch some code, you'll know more about it than before. So why make it perfect now?
76. The lo!ery factor Thanks to https://twitter.com/aaronjrandall for the term
78. Metrics, metrics, metrics
83. Tooling
84. hashtag fatigue
85. Migrations are a good excuse to upgrade your tools.
86. By providing a mix of migration tasks (big, small, visual, "under the hood", tooling), we're able to keep work fun and interesting
87. Talking
88. The most important people to convince are not in your tech team.
89. And they don't care about frameworks
90. "Well, Angular 1 is reaching end of life and React offers a much be!er component model that fits our ideas of how to build so"ware"
91. "React's lifecycle methods and small API is easier for developers to learn"
92. "React's state model is less magical; its unidirectional data flow really simplifies code and makes it easier to reason about"
94. "Right now when you ask us for a new feature, or bug fix, it's hard and takes a long time to fix and have confidence that we've not inadvertently broken anything else"
95. "We will improve our mobile load time + performance so users on mobiles should see fewer issues and have a nicer experience"
96. Fix bugs that cause pain for other departments
98. Keep people in the loop
99. Deal with !
100. http://gunshowcomic.com/648
101. We put a lot of work into making sure things don't go wrong on production. But unfortunately they will, at some point.
102. There are two types of developer 3 3 shamelessly stolen from Twitter! https://twitter.com/beerops/status/866808660030345218
103. Those who have broken production Those who are about to break production
104. Apologies to the 3 people who bought tickets for a concert on the wrong day in Tokyo because of me ! We did fix it though and sort these people out! :)
105. 1. What? went wrong 2. Why? did we not catch it 3. How? did we fix it 4. How? will we prevent it happening again
108. It's a two way street
109. Takeaways
110. 1. Don't migrate for the sake of it
111. 2. Plan, plan and plan again
112. 3. Cross business communication is so important.
113. 4. Prioritise based on pain points in your current application
114. 5. Mix up tasks based on difficulty + type to keep it interesting
115. 6. Have metrics to track progress internally and externally
116. 7. Don't expect to migrate perfectly the first time
117. Thank you ! @Jack_Franklin ! Please come and say hello :) Pictures from pixabay.com