Combined PDF download sometimes corrupted (large lists)

[wvengen]

Some members report that they can't download the combined article and/or ordergroup PDFs at all, which is served by the current_orders plugin. Sometimes re-downloading makes it work, but apparently not always.

Possible solutions (perhaps):

• Stream PDF
• Generate PDF in background job (good idea anyway), re-generate when something changes
• Download in smaller fragments

[wvengen]

Blocker for VKMK dry ordering, since that will generate even larger PDFs.

[wvengen]

I haven't found prior work regarding streaming PDFs with prawn. Advice is background job.

Step 1

• Make sure all data is preloaded and we can figure out whether a PDF is stale or not.

Perhaps this already improves loading times, in case missing preloading is the problem here.

Step 2 (when needed)

• Move PDF rendering to background job
• If PDF isn't up-to-date, start background job
• If PDF is up-to-date, serve generated file
• Add animating 'working on it' icon to download button if background isn't finished yet
• If PDF isn't up-to-date, wait for a couple of seconds before responding - serve if already finished

First do this upstream, then move it here.

[wvengen]

I think Step 1 will fix this. Let's see.
If it remains a problem, please reopen.

[wvengen]

This may not be fully solved yet :(