Merge pull request #633 from gre/lru-cache-on-selectexchange

add a cache on SelectExchange & getEstimatedFees

src/api/Fees.js

@@ -1,5 +1,6 @@
 // @flow
 import invariant from 'invariant'
+import LRU from 'lru-cache'
 import type { Currency } from '@ledgerhq/live-common/lib/types'
 import createCustomErrorClass from 'helpers/createCustomErrorClass'
 import { blockchainBaseURL } from './Ledger'
@@ -11,10 +12,20 @@ export type Fees = {
   [_: string]: number,
 }
 
+const cache = LRU({
+  maxAge: 5 * 60 * 1000,
+})
+
 export const getEstimatedFees = async (currency: Currency): Promise<Fees> => {
+  const key = currency.id
+  let promise = cache.get(key)
+  if (promise) return promise.then(r => r.data)
   const baseURL = blockchainBaseURL(currency)
   invariant(baseURL, `Fees for ${currency.id} are not supported`)
-  const { data, status } = await network({ method: 'GET', url: `${baseURL}/fees` })
+  promise = network({ method: 'GET', url: `${baseURL}/fees` })
+  cache.set(key, promise)
+  const { data, status } = await promise
+  if (status < 200 || status >= 300) cache.del(key)
   if (data) {
     return data
   }

src/components/SelectExchange.js

@@ -1,6 +1,7 @@
 // @flow
 import React, { Component } from 'react'
 import { translate } from 'react-i18next'
+import LRU from 'lru-cache'
 import type { Currency } from '@ledgerhq/live-common/lib/types'
 import type { Exchange } from '@ledgerhq/live-common/lib/countervalues/types'
 import logger from 'logger'
@@ -10,6 +11,18 @@ import Text from 'components/base/Text'
 import CounterValues from 'helpers/countervalues'
 import type { T } from 'types/common'
 
+const cache = LRU({ max: 100 })
+
+const getExchanges = (from: Currency, to: Currency) => {
+  const key = `${from.ticker}_${to.ticker}`
+  let promise = cache.get(key)
+  if (promise) return promise
+  promise = CounterValues.fetchExchangesForPair(from, to)
+  promise.catch(() => cache.del(key)) // if it's a failure, we don't want to keep the cache
+  cache.set(key, promise)
+  return promise
+}
+
 class SelectExchange extends Component<
   {
     from: Currency,
@@ -65,7 +78,7 @@ class SelectExchange extends Component<
     const { _loadId } = this
     const { from, to } = this.props
     try {
-      const exchanges = await CounterValues.fetchExchangesForPair(from, to)
+      const exchanges = await getExchanges(from, to)
       if (!this._unmounted && this._loadId === _loadId) {
         this.setState({ exchanges })
       }