Embedded PDFs aren't always displayed

Bug #1508300 reported by Kristina Hoeppner on 2015-10-21
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Mahara
Low
Unassigned

Bug Description

Noticed in Mahara 1.10; testing on 15.04 and 15.10 needed:

When a page contains many embedded PDFs, the following can happen (all at once):
- some PDFs are displayed
- others show an error message
- others show a Mahara login box
- you can be logged out completely

An initial investigation couldn't replicate the issue successfully and it seemed to happen intermittently. From what we gathered, it seems to be a rendering / loading / overloading issue: Too many instances of pdf.js try to be loaded at the same time causing timeouts and other weird behavior.

I see two possibilities:
1. Limit the number of PDFs that can be embedded on a page
2. Load PDF blocks progressively one after the other

I don't know if the second option would mitigate the problem or not. The first one could be limiting user's creativity, but would prevent endless waiting for a page to load with the content.

Further insight is needed before a final decision can be made on how to continue from here.

Changed in mahara:
assignee: nobody → Cecilia Vela Gurovic (ceciliavg)
assignee: Cecilia Vela Gurovic (ceciliavg) → nobody
Robert Lyon (robertl-9) wrote :

This does indeed sound like a rendering issue with too much browser resource being taken up to handle the pdfs. I suspect the bigger the pdf the more resources it will take to render.

So having 6 small pdfs may work fine but 3 big pdfs fail as each page of the pdf takes resources to render.

So it might be easiest to have a warning in the pdf configuration form warning about the resource intensiveness.

Robert Lyon (robertl-9) on 2017-10-16
Changed in mahara:
importance: High → Low
status: Confirmed → In Progress
milestone: none → 18.04.0

Reviewed: https://reviews.mahara.org/8149
Committed: https://git.mahara.org/mahara/mahara/commit/51fa305e871c2b5f5c92a5e92c89105afbd48adf
Submitter: Robert Lyon (<email address hidden>)
Branch: master

commit 51fa305e871c2b5f5c92a5e92c89105afbd48adf
Author: Robert Lyon <email address hidden>
Date: Mon Oct 16 20:45:35 2017 +1300

Bug 1508300: Adding notice to PDF block config

About the danger of displaying big PDF files

behatnotneeded

Change-Id: I451c6daafc0d1fa537e4d3fdeb16d164be92ac0a
Signed-off-by: Robert Lyon <email address hidden>

Robert Lyon (robertl-9) on 2017-12-07
Changed in mahara:
status: In Progress → Fix Committed
Robert Lyon (robertl-9) on 2018-04-05
Changed in mahara:
status: Fix Committed → Fix Released
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