CloudWatch Logsで特定の文字列を検知したらLambda(node.js)でメール通知する

const aws  = require('aws-sdk');
const zlib = require('zlib');
const sns  = new aws.SNS();

const arn     = process.env.SNS_TOPIC_ARN;
const subject = process.env.EMAIL_SUBJECT;

exports.handler = async (event, context, callback) => {

    // CloudWatchLogsデータをデコード
    const payload     = Buffer.from(event.awslogs.data, 'base64');
    const unzipeddata = zlib.unzipSync(payload);  
    const logdata     = JSON.parse(unzipeddata.toString('utf8'));        
    const logs        = JSON.stringify(logdata,null,2);

    // メッセージ設定
    const params = {
        Message: logs, 
        Subject: subject,
        TopicArn: arn
    };

    // SNSに送信
    // https://docs.aws.amazon.com/ja_jp/sdk-for-javascript/v2/developer-guide/sns-examples-publishing-messages.html
    var publishTextPromise = sns.publish(params).promise();
    publishTextPromise.then(
        function(data) {
            console.log(`Message ${params.Message} sent to the topic ${params.TopicArn}`);
            console.log("MessageID is " + data.MessageId);
        }).catch(
            function(err) {
            console.error(err, err.stack);
        }
    );

    callback(null,logs);

};