Reading the data written to s3 by Amazon Kinesis Firehose stream

Question

I am writing record to Kinesis Firehose stream that is eventually written to a S3 file by Amazon Kinesis Firehose.

My record object looks like

ItemPurchase {
    String personId,
    String itemId
}

The data is written to S3 looks like:

{"personId":"p-111","itemId":"i-111"}{"personId":"p-222","itemId":"i-222"}{"personId":"p-333","itemId":"i-333"}

NO COMMA SEPERATION.

NO STARTING BRACKET as in a Json Array

[

NO ENDING BRACKET as in a Json Array

]

I want to read this data get a list of ItemPurchase objects.

List<ItemPurchase> purchases = getPurchasesFromS3(IOUtils.toString(s3ObjectContent))

What is the correct way to read this data?

Answer 1

It boggles my mind that Amazon Firehose dumps JSON messages to S3 in this manner, and doesn't allow you to set a delimiter or anything.

Ultimately, the trick I found to deal with the problem was to process the text file using the JSON raw_decode method

This will allow you to read a bunch of concatenated JSON records without any delimiters between them.

Python code:

import json

decoder = json.JSONDecoder()

with open('giant_kinesis_s3_text_file_with_concatenated_json_blobs.txt', 'r') as content_file:

    content = content_file.read()

    content_length = len(content)
    decode_index = 0

    while decode_index < content_length:
        try:
            obj, decode_index = decoder.raw_decode(content, decode_index)
            print("File index:", decode_index)
            print(obj)
        except JSONDecodeError as e:
            print("JSONDecodeError:", e)
            # Scan forward and keep trying to decode
            decode_index += 1