CI flakiness with HWP files

[apyrgio]

Our CI tests fail from time to time when converting our sample .hwp/.hwpx files. For example, see this CI test run: https://github.com/freedomofpress/dangerzone/actions/runs/11450930480/job/31859301008#step:10:991. This failures are intermittent, since the tests pass if we kick the CI job one more time.

The failed jobs don't report any helpful error message, so we need to dig deeper.

[apyrgio]

We can run the HWP conversion locally in a tight loop:

$ while poetry run ./dev_scripts/dangerzone-cli <(base64 -d tests/test_docs_external/sample-hwp.hwp.b64) --output-filename /tmp/test-safe.pdf ; do sleep 1; done

I've left it running for a few minutes, and I haven't encountered an error yet. The logs I get from the container are:

----- DOC TO PIXELS LOG START -----
Installing LibreOffice extension 'h2orestart.oxt'
Converting to PDF using LibreOffice
Converting page 1/6 to pixels
Converting page 2/6 to pixels
Converting page 3/6 to pixels
Converting page 4/6 to pixels
Converting page 5/6 to pixels
Converting page 6/6 to pixels
Converted document to pixels
[COMMAND] unzip -d /usr/lib/libreoffice/share/extensions/h2orestart.oxt/ /libreoffice_ext/h2orestart.oxt
Archive:  /libreoffice_ext/h2orestart.oxt
  inflating: icon/H2Orestart.png
  inflating: description.xml
  inflating: description/desc_en.txt
  inflating: H2Orestart.jar
  inflating: description/desc_ko.txt
  inflating: registry/H2Orestart_types.xcu
  inflating: logger.properties
  inflating: registry/H2Orestart_filters.xcu
  inflating: registry/TypeDetection.xcu
  inflating: META-INF/manifest.xml
[COMMAND] libreoffice --headless --safe-mode --convert-to pdf --outdir /tmp /tmp/input_file
OpenJDK 64-Bit Server VM warning: Can't detect primordial thread stack location - find_vma failed
OpenJDK 64-Bit Server VM warning: Can't detect primordial thread stack location - find_vma failed
OpenJDK 64-Bit Server VM warning: Can't detect primordial thread stack location - find_vma failed
convert /tmp/input_file as a Writer document -> /tmp/input_file.pdf using filter : writer_pdf_Export
----- DOC TO PIXELS LOG END -----

This line may point to a race condition if we run it hundreds of times, but I'm not sure:

OpenJDK 64-Bit Server VM warning: Can't detect primordial thread stack location - find_vma failed

[almet]

If there are some tests which are known to be unstable, one way to not bother too much about them is to rerun them with pytest-rerun-failures (yeah, this is a day where I propose pytest-* related tools ! 🍵 while waiting for CI to run).

(of course, it's better to investigate a bit first, but my experience is that in some cases it's not easy to find the culprit).

[apyrgio]

Oh, I didn't know about this tool. It's interesting, but I'm afraid it may mask race conditions that we need to know about :/

[almet]

Yup, I think this should be used only if we don't have the time / we don't find / we can't fix the race condition 👍