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node-rate-limiter で DynamoDB への putItem をレート制限する
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'use strict'; | |
const { RateLimiter } = require('limiter'); | |
// プロビジョニングされた WCU | |
const PROVISIONED_WCU = 5; | |
/** | |
* DynamoDB のレートリミッターを作成する | |
* | |
* @param {number} capacity - キャパシティユニット | |
*/ | |
function createDynamoDBLimiter(capacity) { | |
return new RateLimiter(capacity, 'second'); | |
} | |
/** | |
* RateLimiter#removeTokens を Promise にラッピングする | |
* https://github.com/jhurliman/node-rate-limiter/issues/52 | |
* @param {number} count | |
* @param {RateLimiter} limiter | |
*/ | |
function removeTokens(count, limiter) { | |
return new Promise((resolve, reject) => { | |
limiter.removeTokens(count, (err, remainingRequests) => { | |
if (err) return reject(err); | |
resolve(remainingRequests); | |
}); | |
}); | |
} | |
/** | |
* dynamodb.putItem のモック | |
*/ | |
function putItem(item) { | |
return { | |
promise: () => | |
new Promise(resolve => { | |
setTimeout(() => { | |
console.log(item); | |
resolve(item); | |
}, 100); | |
}), | |
}; | |
} | |
const items = [...Array(20).keys()]; // [0..20] | |
const dynamodbLimiter = createDynamoDBLimiter(PROVISIONED_WCU); | |
// 残キャパシティユニットを考慮して直列に実行する | |
const promise = items.reduce((promise, item) => { | |
return promise | |
.then(() => removeTokens(1, dynamodbLimiter)) | |
.then(() => putItem(item).promise()); | |
}, Promise.resolve()); | |
promise.then(() => console.log('finished')); |
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