Reusing bundles in embedded tectonic

[scodesido-at-proton]

I'm using tectonic to render PDFs from TeX inside an app (a web server). Right now I have to call Cache::open() to get a new bundle every time I want to render, because as far as I can see, the .bundle method of the SessionBuilder takes ownership of the Bundle object, which cannot be cloned.

This doesn't seem very clean, since I use the bundle as read-only so I feel I should only create it once. On top I have the feeling this is the cause behind a weird memory leak I see, as memory use keeps growing by about 2 MiB every time I render a PDF.

What would be the "right" way to use the bundles in such a context?