I'm using nginx reverse proxy cache with gzip enabled. However, I got some problems from android applications http requests to my rails json web service. It seems when I turn off reverse proxy cache, it works ok because the response header comes without gzip. Therefore, I think the problem caused from gzip. What is the most appropriate level of gzip compression?

gzip  on;
gzip_http_version 1.0;
gzip_vary on;
gzip_comp_level 6;
gzip_proxied any;
gzip_types text/plain text/css text/javascript application/javascript application/json application/x-javascript text/xml application/xml application/xml+rss;