Thumbnailing Large/Complex pdfs can blow heap

[wezell]

When trying to generate thumbnails for PDFs, we make use of an Apache library called PDFBox. The issue is that when we try to thumbnail these pdfs, it can overload the servers and blow server heap space. This is a known issue with the library and something they have addressed in later versions.

It is easy to reproduce - when I try to thumbnail this PDF locally I get an OOM exception. At best, we should be able to thumbnail PDFs without blowing heap, regardless of how long it takes.
Here is a fat pdf that blows up:
neuroscience2009.pdf

[wezell]

What this does:

• Adds a 10 slot semaphore to only allow 10 Image Filtering threads at a time. This can be configured as needed by setting IMAGE_GENERATION_SIMULTANEOUS_REQUESTS to a higher number.
• Updates PDFBox version to 2.0.27
• Limits available memory for resizing PDFs
• setSubsamplingAllowed(true) allows for PDFBox to use less memory

[yolabingo]

related cloud support ticket https://dotcms.zendesk.com/agent/tickets/109178

[rjvelazco]

Passed Internal QA

Docker Image: 23.01_a953eb1e_SNAPSHOT

Note For QA

It may take a while, it took me 30 minutes until could see the thumbnail.

[bryanboza]

Fixed, tested locally and it is taken like 10/15 minutes to show the thumbnail, which is not great, but is not killing the server. Then we are ok for now.

Passed QA. Tested on release-23.01 // Docker // FF