question: @ Override public String append ( String path , InputStream is ) throws MalformedURLException , IOException , AuthenticationException { String resp = null ; ensureValidToken ( ) ; String spec = MessageFormat . format ( "/webhdfs/v1/{0}?op=APPEND&user.name={1}" , URLUtil . encodePath ( path ) , this . principal ) ; String redirectUrl = null ; HttpURLConnection conn = authenticatedURL . openConnection ( new URL ( new URL ( httpfsUrl ) , spec ) , token ) ; conn . setRequestMethod ( "POST" ) ; conn . setInstanceFollowRedirects ( false ) ; conn . connect ( ) ; logger . info ( "Location:" + conn . getHeaderField ( "Location" ) ) ; resp = result ( conn , true ) ; if ( conn . getResponseCode ( ) == 307 ) redirectUrl = conn . getHeaderField ( "Location" ) ; conn . disconnect ( ) ; if ( redirectUrl != null ) { conn = authenticatedURL . openConnection ( new URL ( redirectUrl ) , token ) ; conn . setRequestMethod ( "POST" ) ; conn . setDoOutput ( true ) ; conn . setDoInput ( true ) ; conn . setUseCaches ( false ) ; conn . setRequestProperty ( "Content-Type" , "application/octet-stream" ) ; final int _SIZE = is . available ( ) ; conn . setRequestProperty ( "Content-Length" , "" + _SIZE ) ; conn . setFixedLengthStreamingMode ( _SIZE ) ; conn . connect ( ) ; OutputStream os = conn . getOutputStream ( ) ; copy ( is , os ) ; is . close ( ) ; os . close ( ) ; resp = result ( conn , true ) ; conn . disconnect ( ) ; } return resp ; }
target:  curl -i -X POST "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=APPEND[&buffersize=<INT>]"