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February 19, 2017 23:04
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CircuitBreaker with Promises
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const handleResolve = (breaker) => (value) => { | |
breaker.state = closed | |
breaker.errorCount = 0 | |
return Promise.resolve(value) | |
} | |
const handleReject = (breaker) => (reason) => { | |
breaker.errorCount += 1 | |
breaker.state = (breaker.errorCount >= breaker.maxErrorCount ? opened : closed) | |
if (breaker.state === opened) setTimeout(() => breaker.state = halfOpened, breaker.resetTimeout) | |
return Promise.reject(reason) | |
} | |
const closed = (breaker, argsList) => { | |
const timeoutPromise = new Promise((resolve, reject) => setTimeout(() => reject('timeout'), breaker.callTimeout)) | |
return Promise.race([ timeoutPromise, breaker.f(...argsList) ]).then(handleResolve(breaker)).catch(handleReject(breaker)) | |
} | |
const halfOpened = (breaker, argsList) => { | |
breaker.state = opened | |
return closed(breaker, argsList) | |
} | |
const opened = (breaker, argsList) => { | |
return Promise.reject('breaker_opened') | |
} | |
export const protect = (f, { maxErrorCount=5, resetTimeout=1000, callTimeout=5000 } = {}) => { | |
const breaker = { f, maxErrorCount, resetTimeout, callTimeout, errorCount: 0, state: closed } | |
return (...argsList) => breaker.state(breaker, argsList) | |
} | |
/* | |
const resolvesFast = (x) => Promise.resolve(x) | |
const rejectsFast = (x) => Promise.reject(x) | |
const resolvesSlow = (x) => new Promise((resolve, reject) => setTimeout(() => resolve(x), 5000)) | |
const rejectsSlow = (x) => new Promise((resolve, reject) => setTimeout(() => reject(x), 5000)) | |
const main = async (fn) => { | |
try { | |
const value = await fn(1) | |
console.log('value', value) | |
} catch (reason) { | |
console.log('reason', reason) | |
} | |
} | |
main(protect(resolvesSlow, { callTimeout:1000 })) | |
*/ |
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