receiveSQSMessage.js

'use strict'
const AWS = require('aws-sdk');
// SQS の QueueName
const SQS_QUEUE_NAME = 'testQueue'
// 最大で取りたいメッセージ数
const SQS_RECEIVE_LIMIT = 100;
// receiveMessage メソッドの params.MaxNumberOfMessages に渡す数(1 〜 10)
const SQS_RECEIVE_MESSAGE_MAX = 10;

exports.handler = (event, context) => {
    console.log('event', event);
    let queueUrl;
    const sqs = new AWS.SQS();
    
    const promiseCB = (resolve, reject) => {
        return (err, result) => {
           if (err) {
               reject(err);
               return ;
           }
           resolve(result);
        }
    }
    const throughP = (result) => {
        return new Promise((resolve, reject) => {
            resolve(result);
        });
    }
    const createP = (params) => {
        return new Promise((resolve, reject) => {
            sqs.createQueue(params, promiseCB(resolve, reject));
        });
    }
    const checkSizeP = (params) => {
        return new Promise((resolve, reject) => {
            sqs.getQueueAttributes(params, promiseCB(resolve, reject));
        });
    }
    const recieveMessagesP = (params) => {
        return new Promise((resolve, reject) => {
            sqs.receiveMessage(params, promiseCB(resolve, reject));
        });
    }

    createP({
        QueueName: SQS_QUEUE_NAME
    }).then((result) => {
        console.log('createP', result);
        queueUrl = result.QueueUrl
        return checkSizeP({
            QueueUrl: queueUrl,
            AttributeNames: [
                'ApproximateNumberOfMessages',
            ]
        });
    }).then((result) => {
        console.log('checkSizeP', result);
        if (result.Attributes.ApproximateNumberOfMessages === '0') {
            return throughP(result);
        }
        
        const receiveLimit = Math.min(SQS_RECEIVE_LIMIT, parseInt(result.Attributes.ApproximateNumberOfMessages, 10));
        const loop = Math.ceil(receiveLimit / SQS_RECEIVE_MESSAGE_MAX);
        return Promise.all(
            new Array(loop)
                .fill(0)
                .map((v, i) => {
                    return recieveMessagesP({
                        QueueUrl: queueUrl,
                        MaxNumberOfMessages: SQS_RECEIVE_MESSAGE_MAX,
                    });
                })
        );
    }).then((result) => {
        const messages = result.reduce((prev, res) => {
            return prev.concat(res.Messages);
        }, []);
        return throughP(messages.filter((v) => {
            return (v instanceof Object) && v.Body
        }));
    }).then((result) => {
        console.log('context.done', result);
        context.done(null, result);
    }).catch((err) => {
        console.error(err);
        context.done(err);
    });
}