INFO: Error parsing HTTP request header
Note: further occurrences of HTTP header parsing errors will be logged at DEBUG level.
java.lang.IllegalArgumentException: R
Solved!
I was using HTTP GET instead of HTTP POST.
Technically I have seen HttpGet will have issue if the URL length goes beyond 2000 characters. In that case, it's better to use HttpPost or split the URL.
Browsers have limits ranging on the 2kb - 8kb