ApacheFOP svg background very slow

I'm using ApacheFOP to render some PDFs. In these PDF I draw a rounded BOX using SVG for the edges:

<fo:table-cell
    number-columns-spanned="2"
    background-image="/images/top-left.svg"
    background-repeat="no-repeat">
        <fo:block/>
</fo:table-cell>

where the top-left.svg file is pretty simple:

<svg width="10px" height="10px" xmlns="http://www.w3.org/2000/svg">
    <circle cx="10px" cy="10px" r="9.5px" stroke="black" stroke-width="1px" fill="none" />
</svg>

The same is repeated for top-right, bottom-left and bottom-right.

The problem is that, after updating from ApacheFOP 0.95 to ApacheFOP 2.1 the rendering in the production server takes ~15 seconds for each SVG. I cannot reproduce the issue on my computer.

Both my developer desktop and the production server are running Linux.

Is there any system factor that could slow down the SVG rendering so much?

Thanks

Solution

The delay was caused by the downloading of the DTD schema of each SVG. It was hard to spot it because the download was performed by Barcode4J and not by ApacheFOP itself. More specifically it was the BarcodePreloader class that tried to parse the SVG since it was called before PreloaderSVG. We temporarily resolved removing the DTD declaration from the SVG files.