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PP-778: implement the exchange cache (#87)
* feat: implement an exchange cache * feat(CachedExchangeApi): cached value retrieved from coingecko for 60 seconds * fix: change the pricer to use always the same exchange api instead of creating one for each request * style: apply format rules * chore: rename builders to exchanges
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,57 @@ | ||
| import log from 'loglevel'; | ||
| import type { ExchangeApi } from './BaseExchangeApi'; | ||
| import type { BigNumber as BigNumberJs } from 'bignumber.js'; | ||
|
|
||
| export type RateWithExpiration = { | ||
| rate: BigNumberJs; | ||
| expirationTime: number; | ||
| }; | ||
|
|
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| export class ExchangeApiCache implements ExchangeApi { | ||
| constructor( | ||
| private exchangeApi: ExchangeApi, | ||
| private expirationTimeInMillisec: number, | ||
| private cache: Map<string, RateWithExpiration> = new Map< | ||
| string, | ||
| RateWithExpiration | ||
| >() | ||
| ) {} | ||
|
|
||
| public async queryExchangeRate( | ||
| sourceCurrency: string, | ||
| targetCurrency: string | ||
| ): Promise<BigNumberJs> { | ||
| const key = getKeyFromArgs(sourceCurrency, targetCurrency); | ||
| const now = Date.now(); | ||
| const cachedRate = this.cache.get(key); | ||
| if (!cachedRate || cachedRate.expirationTime <= now) { | ||
| log.debug( | ||
| 'CachedExchangeApi: value not available or expired', | ||
| cachedRate | ||
| ); | ||
| const rate = await this.exchangeApi.queryExchangeRate( | ||
| sourceCurrency, | ||
| targetCurrency | ||
| ); | ||
| const expirationTime = now + this.expirationTimeInMillisec; | ||
| this.cache.set(key, { expirationTime, rate }); | ||
| log.debug('ExchangeApiCache: storing a new value', key, { | ||
| expirationTime, | ||
| rate, | ||
| }); | ||
|
|
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| return rate; | ||
| } | ||
| log.debug( | ||
| 'ExchangeApiCache: value available in cache, API not called', | ||
| cachedRate | ||
| ); | ||
|
|
||
| return cachedRate.rate; | ||
| } | ||
| } | ||
|
|
||
| export const getKeyFromArgs = ( | ||
| sourceCurrency: string, | ||
| targetCurrency: string | ||
| ) => `${sourceCurrency}->${targetCurrency}`; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,96 @@ | ||
| import BigNumber from 'bignumber.js'; | ||
| import { expect } from 'chai'; | ||
| import { | ||
| RateWithExpiration, | ||
| ExchangeApiCache, | ||
| getKeyFromArgs, | ||
| } from '../../../src/api/pricer/ExchangeApiCache'; | ||
| import type { ExchangeApi } from 'src/api/pricer/BaseExchangeApi'; | ||
| import sinon from 'sinon'; | ||
|
|
||
| describe('ExchangeApiCache', function () { | ||
| const sourceCurrency = 'source'; | ||
| const targetCurrency = 'target'; | ||
| const valueFromExchange = '1'; | ||
| let fakeExchangeAPI: ExchangeApi; | ||
|
|
||
| beforeEach(function () { | ||
| fakeExchangeAPI = { | ||
| queryExchangeRate: sinon.fake.resolves(new BigNumber(valueFromExchange)), | ||
| }; | ||
| }); | ||
|
|
||
| it('should perform a call to the inner exchange if the value is not cached', async function () { | ||
| const cache = new Map<string, RateWithExpiration>(); | ||
| const cachedExchangeApi = new ExchangeApiCache(fakeExchangeAPI, 100, cache); | ||
| const rate = await cachedExchangeApi.queryExchangeRate( | ||
| sourceCurrency, | ||
| targetCurrency | ||
| ); | ||
|
|
||
| expect(rate.toString()).to.be.eq(valueFromExchange); | ||
| expect(fakeExchangeAPI.queryExchangeRate).to.have.been.calledWithExactly( | ||
| sourceCurrency, | ||
| targetCurrency | ||
| ); | ||
| }); | ||
|
|
||
| it('should store the value if it is not cached', async function () { | ||
| const cache = new Map<string, RateWithExpiration>(); | ||
| const cachedExchangeApi = new ExchangeApiCache(fakeExchangeAPI, 100, cache); | ||
| const rate = await cachedExchangeApi.queryExchangeRate( | ||
| sourceCurrency, | ||
| targetCurrency | ||
| ); | ||
| const key = getKeyFromArgs(sourceCurrency, targetCurrency); | ||
|
|
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| expect(rate.toString()).to.be.eq(valueFromExchange); | ||
| expect(cache.get(key)?.rate.toString()).to.be.eq(valueFromExchange); | ||
| }); | ||
|
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||
| it('should perform a call to the inner exchange if the cached value is expired', async function () { | ||
| const previouslyStoredValue = 100; | ||
| const cache: Map<string, RateWithExpiration> = new Map(); | ||
| const key = getKeyFromArgs(sourceCurrency, targetCurrency); | ||
| // 1 second ago | ||
| const expirationTime = Date.now() - 1_000; | ||
| cache.set(key, { | ||
| rate: new BigNumber(previouslyStoredValue), | ||
| expirationTime, | ||
| }); | ||
| const cachedExchangeApi = new ExchangeApiCache(fakeExchangeAPI, 100, cache); | ||
| const rate = await cachedExchangeApi.queryExchangeRate( | ||
| sourceCurrency, | ||
| targetCurrency | ||
| ); | ||
|
|
||
| expect(rate.toString()).to.be.eq(valueFromExchange); | ||
|
|
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| expect(fakeExchangeAPI.queryExchangeRate).to.have.been.calledWithExactly( | ||
| sourceCurrency, | ||
| targetCurrency | ||
| ); | ||
| expect(cache.get(key)?.rate.toString()).to.be.eq(valueFromExchange); | ||
| }); | ||
|
|
||
| it('should not perform a call to the inner exchange if the cached value is not expired', async function () { | ||
| const cache: Map<string, RateWithExpiration> = new Map(); | ||
| const key = getKeyFromArgs(sourceCurrency, targetCurrency); | ||
| // in 10 seconds | ||
| const expirationTime = Date.now() + 10_000; | ||
| const cachedRate = new BigNumber(100); | ||
| cache.set(key, { | ||
| rate: cachedRate, | ||
| expirationTime, | ||
| }); | ||
| const cachedExchangeApi = new ExchangeApiCache(fakeExchangeAPI, 100, cache); | ||
| const rate = await cachedExchangeApi.queryExchangeRate( | ||
| sourceCurrency, | ||
| targetCurrency | ||
| ); | ||
|
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| expect(rate.toString()).to.be.eq(cachedRate.toString()); | ||
|
|
||
| expect(fakeExchangeAPI.queryExchangeRate).not.to.have.been.called; | ||
| }); | ||
| }); |
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