Use default access log format will result in logs without break lines. I have to attach a \n in format string.

"format": "[%START_TIME%] "%REQ(:METHOD)%" "%REQ(X-ENVOY-ORIGINAL-PATH?:PATH)%" %PROTOCOL% %RESPONSE_CODE% %FAILURE_REASON% %BYTES_RECEIVED% %BYTES_SENT% %DURATION% "%RESP(X-ENVOY-UPSTREAM-SERVICE-TIME)%" "%REQ(X-FORWARDED-FOR?X-ENVOY-EXTERNAL-ADDRESS)%" "%REQ(X-REQUEST-ID)%" "%REQ(:AUTHORITY)%" "%UPSTREAM_HOST%""

Tested on ubuntu 14.04 with envoy 1.0.