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Front Trends: Migrating complex software
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Jack Franklin
May 25, 2017
Technology
1
810
Front Trends: Migrating complex software
A talk about migrating complex software, based on my experience of Angular => React at Songkick.
Jack Franklin
May 25, 2017
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Transcript
! From Angular to React @Jack_Franklin
Migrating complex so!ware
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The Store
Started 2 years ago, built on Angular 1 Tickets being
sold constantly Used by our flagship clients
The store works well. But changing it is very tricky.
Legacy codebase An old version of Angular 1 Feature bloat
Original developers have gone
We can't iterate quickly, respond to bug reports, or build
new features in a timely manner. We lack confidence in our system.
The Four T's — Tech — Tests — Team —
Talking
Tech
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Big bang vs incremental
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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
https://www.martinfowler.com/bliki/ StranglerApplication.html
http://2017.theleaddeveloper.com/ | @saleandro
We shipped migrated code the day a!er starting this migration.
The Theory Components (or directives in Angular)
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The plan
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Migrating a component
1. Find all dependencies that a directive uses
2. Migrate all of those one by one to React
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> ) } }
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>
None
With ngReact <li> <h2>Rihanna at The O2</h2> <react-component name="ListingsButton" props="..."
/> </li>
We can continue this strategy, migrating the other components to
React: <li> <react-component name="ListingsTitle" props="..." /> <react-component name="ListingsButton" props="..." /> </li>
None
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> ) } }
And update our template <react-component name="ListingsItem" props="..." />
None
And we now rinse and repeat as we replace Angular
with React Forever.
Tests
We cannot break the store
Unit tests Migrated from Angular to React + added to
as appropriate.
https://www.sitepoint.com/test-react-components-jest/
Unit tests are coupled to the implementation code.
Acceptance tests
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Automated tests that are entirely decoupled to the application code.
Because they are slow to run, we keep acceptance tests
to our core user journeys
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
Team
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...
Momentum & Prioritisation
One of the goals of this migration is to make
it easier to fix bugs with confidence.
Pick work based on bugs and churn rate, not code
quality
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Mix larger, multi-week work with short, 1-2 day work, to
keep momentum.
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Break down large work into smaller cards and pull requests
Feature branches
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Release early, release o!en Encourages small pull requests and units
of work
Release early, release o!en Keeps momentum up in the team
and keeps risk to a minimum
Release early, release o!en ! Easier to react 2 to
a bug if release causes it 2 pun very much intended
The scout's rule Always leave things better than when you
found them.
A migrated codebase is not a perfect code base
The next time you touch some code, you'll know more
about it than before. So why make it perfect now?
The lo!ery factor Thanks to https://twitter.com/aaronjrandall for the term
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Metrics, metrics, metrics
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Tooling
hashtag fatigue
Migrations are a good excuse to upgrade your tools.
By providing a mix of migration tasks (big, small, visual,
"under the hood", tooling), we're able to keep work fun and interesting
Talking
The most important people to convince are not in your
tech team.
And they don't care about frameworks
"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"
"React's lifecycle methods and small API is easier for developers
to learn"
"React's state model is less magical; its unidirectional data flow
really simplifies code and makes it easier to reason about"
None
"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"
"We will improve our mobile load time + performance so
users on mobiles should see fewer issues and have a nicer experience"
Fix bugs that cause pain for other departments
None
Keep people in the loop
Deal with !
http://gunshowcomic.com/648
We put a lot of work into making sure things
don't go wrong on production. But unfortunately they will, at some point.
There are two types of developer 3 3 shamelessly stolen
from Twitter! https://twitter.com/beerops/status/866808660030345218
Those who have broken production Those who are about to
break production
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! :)
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
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It's a two way street
Takeaways
1. Don't migrate for the sake of it
2. Plan, plan and plan again
3. Cross business communication is so important.
4. Prioritise based on pain points in your current application
5. Mix up tasks based on difficulty + type to
keep it interesting
6. Have metrics to track progress internally and externally
7. Don't expect to migrate perfectly the first time
Thank you ! @Jack_Franklin ! Please come and say hello
:) Pictures from pixabay.com