Logstash TCP vs UDP newline vs no newline

issue36.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import json
import socket

PORT = 3333


def send(proto, use_trailing_newline):
    if proto == 'UDP':
        sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    else:
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        sock.connect(('127.0.0.1', PORT))

    with_newline = 'with' if use_trailing_newline else 'without'
    for msgnum in range(5):
        # prepare data
        data = dict(message=f'Message via {proto} {with_newline} newline #{msgnum}')
        data = json.dumps(data)
        if use_trailing_newline:
            data += '\n'
        data = bytes(data, 'utf-8')

        # send
        if proto == 'UDP':
            sock.sendto(data, ('127.0.0.1', PORT))
        else:
            sock.sendall(data)

    sock.close()


send(proto='UDP', use_trailing_newline=True)
send(proto='UDP', use_trailing_newline=False)
send(proto='TCP', use_trailing_newline=True)
send(proto='TCP', use_trailing_newline=False)

logstash.conf

	tcp {
		host => "127.0.0.1"
		port => 3333
		mode => server
		codec => json {}
	}
	udp {
		host => "127.0.0.1"
		port => 3333
		codec => json {}
	}

output

{"message":"Message via TCP with newline #0","@version":"1","@timestamp":"2019-04-07T09:14:14.082Z","host":"localhost.localdomain","port":44252}
{"message":"Message via TCP with newline #1","@version":"1","@timestamp":"2019-04-07T09:14:14.082Z","host":"localhost.localdomain","port":44252}
{"message":"Message via TCP with newline #2","@version":"1","@timestamp":"2019-04-07T09:14:14.082Z","host":"localhost.localdomain","port":44252}
{"message":"Message via TCP with newline #3","@version":"1","@timestamp":"2019-04-07T09:14:14.082Z","host":"localhost.localdomain","port":44252}
{"message":"Message via TCP with newline #4","@version":"1","@timestamp":"2019-04-07T09:14:14.082Z","host":"localhost.localdomain","port":44252}
{"message":"Message via TCP without newline #0","@version":"1","@timestamp":"2019-04-07T09:14:14.081Z","host":"localhost.localdomain","port":44254}
{"message":"Message via UDP with newline #0","@version":"1","@timestamp":"2019-04-07T09:14:14.064Z","host":"127.0.0.1"}
{"message":"Message via UDP with newline #1","@version":"1","@timestamp":"2019-04-07T09:14:14.064Z","host":"127.0.0.1"}
{"message":"Message via UDP with newline #2","@version":"1","@timestamp":"2019-04-07T09:14:14.066Z","host":"127.0.0.1"}
{"message":"Message via UDP with newline #3","@version":"1","@timestamp":"2019-04-07T09:14:14.068Z","host":"127.0.0.1"}
{"message":"Message via UDP with newline #4","@version":"1","@timestamp":"2019-04-07T09:14:14.066Z","host":"127.0.0.1"}
{"message":"Message via UDP without newline #0","@version":"1","@timestamp":"2019-04-07T09:14:14.067Z","host":"127.0.0.1"}
{"message":"Message via UDP without newline #1","@version":"1","@timestamp":"2019-04-07T09:14:14.067Z","host":"127.0.0.1"}
{"message":"Message via UDP without newline #2","@version":"1","@timestamp":"2019-04-07T09:14:14.068Z","host":"127.0.0.1"}
{"message":"Message via UDP without newline #3","@version":"1","@timestamp":"2019-04-07T09:14:14.068Z","host":"127.0.0.1"}
{"message":"Message via UDP without newline #4","@version":"1","@timestamp":"2019-04-07T09:14:14.069Z","host":"127.0.0.1"}