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React+Redux @ Scale
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Daniel Cousineau
June 26, 2017
Programming
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330
React+Redux @ Scale
Given at QCon NYC 2017
https://qconnewyork.com/ny2017/presentation/reactredux-scale-talk
Daniel Cousineau
June 26, 2017
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Transcript
React+Redux @ Scale
@dcousineau
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Rules
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“Rules”
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Scalability is the capability of a system, network, or process
to handle a growing amount of work, or its potential to be enlarged to accommodate that growth. – Wikipedia
Part 1: React
Rule: Components should be stateless
Reality: State is the enemy, but also inevitable
onClick(e) { const value = e.target.value; const formatted = value.toUpperCase();
this.setState({value: formatted}); }
onClick() { this.setState((previousState, currentProps) => { return { show: !previousState.show,
}; }); }
onClick(e) { this.setState({value: e.target.value}); this.props.onChange(this.state.value); }
onClick(e) { this.setState({value: e.target.value}, () => { this.props.onChange(this.state.value); }); }
Rule: Don’t use Context, it hides complexity
Reality: Sometimes complexity should be hidden
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class TextCard extends React.Component { static contextTypes = { metatypes:
React.PropTypes.object, }; render() { const {cardData} = this.props; const {metatypes} = this.context; return ( <div> The following is either editable or displayed: <metatypes.text value={cardData.text} onChange={this.props.onChange} /> </div> ) } } function selectCardComponent(cardData) { switch (cardData.type) { case 'text': return TextCard; default: throw new Error(`Invalid card type ${cardData.type}`); } }
class TextCard extends React.Component { static contextTypes = { metatypes:
React.PropTypes.object, }; render() { const {cardData} = this.props; const {metatypes} = this.context; return ( <div> The following is either editable or displayed: <metatypes.text value={cardData.text} onChange={this.props.onChange} /> </div> ) } } function selectCardComponent(cardData) { switch (cardData.type) { case 'text': return TextCard; default: throw new Error(`Invalid card type ${cardData.type}`); } }
const metatypesEdit = { text: class extends React.Component { render()
{ return <input type="text" {...this.props} />; } } } const metatypesView = { text: class extends React.Component { render() { return <span>{this.props.value}</span>; } } }
class CardViewer extends React.Component { static childContextTypes = { metatypes:
React.PropTypes.object }; getChildContext() { return {metatypes: metatypesView}; } render() { const {cardData} = this.props; const CardComponent = selectCardComponent(cardData); return <CardComponent cardData={cardData} /> } }
class CardEditor extends React.Component { static childContextTypes = { metatypes:
React.PropTypes.object }; getChildContext() { return {metatypes: metatypesEdit}; } render() { const {cardData} = this.props; const CardComponent = selectCardComponent(cardData); return <CardComponent cardData={cardData} /> } }
Part 2: Redux
Rule: “Single source of truth” means all state in the
store
Reality: You can have multiple “single sources”
this.state.checked = true;
this.props.checked = true; this.props.checked = true; this.props.checked = true; this.state.checked
= true;
this.props.checked = true; this.props.checked = true; this.props.checked = true; this.props.checked
= true; checked: true connect()();
window.location.*
Rule: Side effects should happen outside the Redux cycle
Reality: This doesn’t mean you can’t have callbacks
function persistPostAction(post, callback = () => {}) { return {
type: 'PERSIST_POST', post, callback }; } function *fetchPostsSaga(action) { const status = yield putPostAPI(action.post); yield put(persistPostCompleteAction(status)); yield call(action.callback, status); } class ComposePost extends React.Component { onClickSubmit() { const {dispatch} = this.props; const {post} = this.state; dispatch(persistPostAction(post, () => this.displaySuccessBanner())); } }
class ViewPostPage extends React.Component { componentWillMount() { const {dispatch, postId}
= this.props; dispatch(fetchPostAction(postId, () => this.logPageLoadComplete())); } }
Rule: Redux stores must be normalized for performance
Reality: You must normalize to reduce complexity
https://medium.com/@dcousineau/advanced-redux-entity-normalization-f5f1fe2aefc5
{ byId: { ...entities }, keyWindows: [`${keyWindowName}`], [keyWindowName]: { ids:
['id0', ..., 'idN'], ...meta } }
{ byId: { 'a': userA, 'b': userB, 'c': userC, 'd':
userD }, keyWindows: ['browseUsers', 'allManagers'], browseUsers: { ids: ['a', 'b', 'c'], isFetching: false, page: 1, totalPages: 10, next: '/users?page=2', last: '/users?page=10' }, allManagers: { ids: ['d', 'a'], isFetching: false } }
function selectUserById(store, userId) { return store.users.byId[userId]; } function selectUsersByKeyWindow(store, keyWindow)
{ return store.users[keyWindow].ids.map(userId => selectUserById(store, userId)); }
function fetchUsers({query}, keyWindow) { return { type: FETCH_USERS, query, keyWindow
}; } function fetchManagers() { return fetchUsers({query: {isManager: true}}, 'allManager'); } function receiveEntities(entities, keyWindow) { return { type: RECEIVE_ENTITIES, entities, keyWindow }; }
function reducer(state = defaultState, action) { switch(action.type) { case FETCH_USERS:
return { ...state, keyWindows: uniq([...state.keyWindows, action.keyWindow]), [action.keyWindow]: { ...state[action.keyWindow], isFetching: true, query: action.query } }; case RECEIVE_ENTITIES: return { ...state, byId: { ...state.byId, ...action.entities.users.byId }, keyWindows: uniq([...state.keyWindows, action.keyWindow]), [action.keyWindow]: { ...state[action.keyWindow], isFetching: false, ids: action.entities.users.ids } }; } }
function reducer(state = defaultState, action) { switch(action.type) { case FETCH_USERS:
return { ...state, keyWindows: uniq([...state.keyWindows, action.keyWindow]), [action.keyWindow]: { ...state[action.keyWindow], isFetching: true, query: action.query } }; case RECEIVE_ENTITIES: return { ...state, byId: { ...state.byId, ...action.entities.users.byId }, keyWindows: uniq([...state.keyWindows, action.keyWindow]), [action.keyWindow]: { ...state[action.keyWindow], isFetching: false, ids: action.entities.users.ids } }; } }
function selectUsersAreFetching(store, keyWindow) { return !!store.users[keyWindow].isFetching; } function selectManagersAreFetching(store) {
return selectUsersAreFetching(store, 'allManagers'); }
function reducer(state = defaultState, action) { switch(action.type) { case UPDATE_USER:
return { ...state, draftsById: { ...state.draftsById, [action.user.id]: action.user } }; case RECEIVE_ENTITIES: return { ...state, byId: { ...state.byId, ...action.entities.users.byId }, draftsById: { ...omit(state.draftsById, action.entities.users.byId) }, keyWindows: uniq([...state.keyWindows, action.keyWindow]), [action.keyWindow]: { ...state[action.keyWindow], isFetching: false, ids: action.entities.users.ids } }; } }
function reducer(state = defaultState, action) { switch(action.type) { case UPDATE_USER:
return { ...state, draftsById: { ...state.draftsById, [action.user.id]: action.user } }; case RECEIVE_ENTITIES: return { ...state, byId: { ...state.byId, ...action.entities.users.byId }, draftsById: { ...omit(state.draftsById, action.entities.users.byId) }, keyWindows: uniq([...state.keyWindows, action.keyWindow]), [action.keyWindow]: { ...state[action.keyWindow], isFetching: false, ids: action.entities.users.ids } }; } }
function selectUserById(store, userId) { return store.users.draftsById[userId] || store.users.byId[userId]; }
function reducer(state = defaultState, action) { switch(action.type) { case UNDO_UPDATE_USER:
return { ...state, draftsById: { ...omit(state.draftsById, action.user.id), } }; } }
Part 3: Scale
Rule: Keep dependencies low to keep the application fast
Reality: Use bundling to increase PERCEIVED performance
class Routes extends React.Component { render() { return ( <Switch>
<Route exact path="/" component={require(‘../home').default} /> <Route path="/admin" component={lazy(require(‘bundle-loader?lazy&name=admin!../admin’))} /> <Route component={PageNotFound} /> </Switch> ); } }
require('bundle-loader?lazy&name=admin!../admin’)
const lazy = loader => class extends React.Component { componentWillMount()
{ loader(mod => this.setState({ Component: mod.default ? mod.default : mod }) ); } render() { const { Component } = this.state; if (Component !== null) { return <Component {...this.props} />; } else { return <div>Is Loading!</div>; } } };
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Rule: Render up-to-date data
Reality: If you got something render it, update it later
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Epilog: Scale?
Rule: Scale is bytes served, users concurrent
Reality: Scale is responding to bytes served and users concurrent
How fast can you deploy?
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Pre: Clear homebrew & yarn caches 1. Reinstall node &
yarn via brew 2. Clone repo 3. Run yarn install 4. Run production build 1. Compile & Minify CSS 2. Compile Server via Babel 3. Compile, Minify, & Gzip via Webpack 190.64s ~3 min
<Feature name="new-feature" fallback={<OldFeatureComponent />}> <NewFeatureComponent /> </Feature>
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Team 1 Team 2 Merge Feature A Merge Feature B
Deploy Deploy OMG ROLLBACK DEPLOY!!! Merge Feature C Merge Bugfix for A Deploy Deploy BLOCKED!!! Deploy
Team 1 Team 2 Merge Feature A Merge Feature B
Deploy Deploy Rollout Flag A Rollout Flag B OMG ROLLBACK FLAG A!!! Merge Feature C Deploy Merge Bugfix for A Deploy Rollout Flag A Rollout Flag C
Can you optimize your directory structure around team responsibilities? If
teams are organized by “product domain”, Can you organize code around product domain?
Final Thoughts
Strict rules rarely 100% apply to your application. Remembering the
purpose behind the rules is valuable.
Code behavior should be predictable and intuitable. Be realistic about
the problem you’re actually solving.
You will not get it perfect the first time. Optimize
your processes for refactoring.
Questions?