Kinesis Firehose putting JSON objects in S3 without seperator comma

Question

Before sending the data I am using JSON.stringify to the data and it looks like this

{"data": [{"key1": value1, "key2": value2}, {"key1": value1, "key2": value2}]}

But once it passes through AWS API Gateway and Kinesis Firehose puts it to S3 it looks like this

    {
     "key1": value1, 
     "key2": value2
    }{
     "key1": value1, 
     "key2": value2
    }

The seperator comma between the JSON objects are gone but I need it to process data properly.

Template in the API Gateway:

#set($root = $input.path('$'))
{
    "DeliveryStreamName": "some-delivery-stream",
    "Records": [
#foreach($r in $root.data)
#set($data = "{
    ""key1"": ""$r.value1"",
    ""key2"": ""$r.value2""
}")
    {
        "Data": "$util.base64Encode($data)"
    }#if($foreach.hasNext),#end
#end
    ]
}

Answer 1

I had this same problem recently, and the only answers I was able to find were basically just to add line breaks ("\n") to the end of every JSON message whenever you posted them to the Kinesis stream, or to use a raw JSON decoder method of some sort that can process concatenated JSON objects without delimiters.

I posted a python code solution which can be found over here on a related Stack Overflow post: https://stackoverflow.com/a/49417680/1546785