Readonly-friendly rootfs support

[igalia]

Readonly-friendly rootfs support

[gil0109]

@philn thank you. Also, if not disabled, then redirected to a tmpfs directory

[aperezdc]

Some of the features which cause writes to disk can be disabled using some of the command line options listed with --help-websettings, for example:

cog --enable-offline-web-application-cache=false \
    --enable-page-cache=false \
    ...

That being said, writable disk access for temporary files may still be needed. You can use the XDG_CACHE_HOME, XDG_DATA_HOME, XDG_RUNTIME_DIR, and so on as defined in the XDG Base Directory Specification, which Cog honors.

Please let us know if doing any of the above (or a combination of both) solves the issue for you.

[gil0109]

@aperezdc Thank you for the information. I will try the XDG variables.

Please note that my version of Cog doesn't have the --help-websettings
$cog --version
0.1.0
$cog --help-websettings
Unknown option --help-websettings

[aperezdc]

@gil0109 You're welcome! The XDG variables should be enough to make Cog write temporary files and caches in whichever path you may prefer. For the --help-websettings you will need a version of Cog newer than commit 1c63839 so I suppose your build is from some older commit — you may need to update your build recipes to pick a more recent revision from the Cog repository.

[gil0109]

@aperezdc

I upgrade to the latest cog (thank you).

I am viewing a 600mb mp4 file.

I am getting the following memory error. Is there something I can do to fix this? If I run the same thing using chromium and raspbian stretch using overlayfs, I don't have this issue. So I am hoping, there's something we can do with cog and webkit.

root@raspberrypi3:~# /usr/sbin/start_cog.sh
Starting Digital Signage
[LibinputServer] Initialization of linux input system succeeded.
Cannot create EGL surfaceless context: missing EGL_KHR_surfaceless_{context,opengl} extension.
Cannot create EGL WPE context: EGL_SUCCESS
Cog-Message: https://sbc-qsystem-prod.pathfinder.gov.bc.ca/sbc.mp4 Load started.
Cog-Message: https://sbc-qsystem-prod.pathfinder.gov.bc.ca/sbc.mp4 Loading...
Cog-Message: https://sbc-qsystem-prod.pathfinder.gov.bc.ca/sbc.mp4 Loaded successfully.
Memory pressure relief: Total: res = 25817088/24981504/-835584, res+swap = 23851008/23187456/-663552

[gil0109]

One more thing, running the video using streamer does not seem tohave this issue:
gst-play-1.0 https://sbc-qsystem-dev.pathfinder.gov.bc.ca/sbc.mp4
Now playing https://sbc-qsystem-dev.pathfinder.gov.bc.ca/sbc.mp4
Prerolling...
Buffering... 100%
0:01:01.9 / 0:22:36.5

[philn]

Chromium doesn't display errors but likely also uses a lot of memory :) The memory pressure message you see is not critical but it would be good to do further investigation anyway.

May I suggest you to subscribe to the WPE mailing list? See https://lists.webkit.org/mailman/listinfo/webkit-wpe

This specific issue you observe is not related with this Cog issue we're discussing in.

[aperezdc]

As mentioned by @philn, the memory pressure handler message is normal, and means that WebKit is trying to return some unused memory back to the system — that's good!

@gil0109 I understand that you have been able to use Cog on your system with read-only rootfs, using the XDG_* variables. Can you confirm whether that approach worked for you? Thanks!

[gil0109]

@aperezdc Absolutely will let you know. Turning on read-only broke a few other items like DHCP so I am working on getting that fixed before I can test and report.

As for the message, as soon as that happens, the video either hangs or the image is flattened to a cm thick. I was hoping to post it on Igalia_WebKit but I will take @philn advice and try to figure out how to use the mailing list to post the issue there. Learning a lot of new things.

[gil0109]

Great news... COG is running successfully with the variables set on a read-only-rootfs.

Thank you for your help!!

export XDG_CACHE_HOME=/tmp
export XDG_DATA_HOME=/tmp
export XDG_CONFIG_HOME=/tmp
export XDG_RUNTIME_DIR=/tmp
export XDG_DATA_DIRS=/tmp
export XDG_RUNTIME_DIR=/tmp
exec /usr/bin/cog ${URL}

[aperezdc]

@gil0109 Thanks for confirming that you got it working 👍

I think we can now close this issue.