GhostScript crashing on some PDF derivatives

[seth-shaw-asu]

GhostScript is "hangs" on some PDFs imagemagick is passing to it during thumbnail processing. This locks the apache/imagemagick thread Crayfish holds and blocks further derivative processing (since Karaf is configured to only process one message per queue at a time). This was discovered when reviewing some of the derivatives that failed to process identified #580.

This issue reports this as being known for the version of GhostScript we have (9.26; the latest available from Ubuntu). The suggested solution is either downgrading GhostScript or upgrading Imagemagick.

The downgrade of GhostScript on Ubuntu is not simple as there are package dependencies involved, nor is the imagemagick upgrade simgple as we rely on the Lyrasis version which includes JP2 support.

The work-around, in the meantime, is to restart karaf (so it drops the stuck derivative request) and apache (so it drops the hung gs thread) on the services server when this happens.

[seth-shaw-asu]

We recently updated Crayfish/Houdini which included the capacity to limit the PDF source to just the first page. This appears to avoid the page/pages that GhostScript was choking on, allowing the thumbnail to generate correctly. 🎊
However, this is still an issue that should probably be resolved someday, so we should degrade its status to low.