While accessing large amount of GIS, I am getting warning "Unable to read image at <URL>. Can't create an ImageInputStream!".
This seems to be known issue due to use of Java Class(i.e. Image IO and IIORegistry), because IIORegistry doesn't by default work well with servlet contexts. Reference:
Below logs are created while loading heavy application:
WARN [renderer.style] - Unable to read image at <URL> : Can't create an ImageInputStream!