Send logs to datadog with custom formatter shows only the first log of multiple ones - ruby

Question

I am trying to send logs to DD (datadog) in such a way that the logs are being received as json and therefore shown properly in the portal through attributes.
My logger is a simple Logger.new(STDOUT, level: Logger::INFO).
If I stick to its standard output, it will in the form
I, [2022-07-30T22:43:35.216846 #1] INFO -- my-app: {"user":"1234"}
which is not really parsable by DD since not a proper JSON. In this case however all the logs appear at least on the DD portal.
Now.. I am trying to format the logs in a JSON manner in this way:
def self.logger
#logger ||= Logger.new(STDOUT, level: Logger::INFO)
#logger.progname = 'my-app'
#logger.formatter = proc do |severity, datetime, progname, msg|
{timestamp: datetime.to_s, progname: progname, severity: severity, correlation: Datadog::Tracing.log_correlation, message: msg}.to_json
end
#logger
end
This is my logger and thanks to this logs are seen properly in DD and parsed correctly because formatted in my app in a proper JSON.
The problem with this approach though seems to be that the logs are sent in 1 full block. Meaning that only the very first log is being visible. Let's say that I want to log this:
my_hash = {"message" => '1', "prop" => '1234'}.to_json
logger.info(my_hash)
my_hash = {"message" => '2', "prop" => '12345'}.to_json
logger.info(my_hash)
only the first log will be shown correctly on the DD portal. Parsed correctly with its message and prop attributes, but nothing about the second log.
Here is the thing, if I see the output of my app locally in the console I see this:
{"timestamp":"2022-07-31 01:15:39 +0200","progname":"my-app","severity":"INFO","correlation":"dd.service=my-app dd.trace_id=2976451780376429536 dd.span_id=0","message":"{"message":"1","prop":"1234"}"}{"timestamp":"2022-07-31 01:15:39 +0200","progname":"my-app","severity":"INFO","correlation":"dd.service=my-app dd.trace_id=2976451780376429536 dd.span_id=0","message":"{"message":"2","prop":"12345"}"}127.0.0.1 - - [31/Jul/2022:01:15:39 +0200] "GET /controller/test_controller HTTP/1.1" 200 - 0.0024
so the 2nd log gets actually outputted! But DD somehow sees only the first log..
(I know there is even a 3rd one shown in this message.. but that's just Sinatra automatic behavior for every http call reaching the api). What do you guys think is the problem?