kinesis firehose transformation, origin: json log, add kinesis approximateArrivalTimestamp to log, append newline string for s3 json line

kinesis-firehose-lambda-newline-arrivedts.js

exports.handler = async (event, context) => {
    const output = event.records.map((record) => {
        
        const arrived_ts = record.approximateArrivalTimestamp;
        const buff = Buffer.from(record.data, 'base64');
        const obj = JSON.parse(buff.toString());
        obj.arrived_ts = arrived_ts;
        record.data = Buffer.from(JSON.stringify(obj) + "\n").toString('base64');
        record.result = 'Ok';
        return record;
    });

    return { records: output };
};