[Bug 648010] New: Better handling of blacklisted plugins: re-scan occasionally, store reason for blacklisting

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=648010
  GStreamer | gstreamer (core) | git

           Summary: Better handling of blacklisted plugins: re-scan
                    occasionally, store reason for blacklisting
    Classification: Platform
           Product: GStreamer
           Version: git
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: Normal
         Component: gstreamer (core)
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: t.i.m at zen.co.uk
         QAContact: gstreamer-bugs at lists.freedesktop.org
                CC: ensonic at sonicpulse.de, thaytan at mad.scientist.com,
                    t.i.m at zen.co.uk, nekohayo at gmail.com
     GNOME version: ---


+++ This bug was initially created as a clone of Bug #503675 +++

<__tim> nekohayo, your registry file is full of BLACKLISTED. The problem isn't
registry file writing or parsing, but that plugins get blacklisted for some
reason
<nekohayo> When does blacklisting occur?
<__tim> nekohayo, when an error occurs when loading the plugin, usually a
missing symbol or library or somesuch
<nekohayo> videomixer was indeed on the gst-inspect blacklist

<__tim> are you sometimes downgrading versions of core or gst-plugins-base?
<nekohayo> no, not that I know of. Downgrading was downright impossible in
ubuntu, and I haven't used downgrade in fedora yet
<__tim> GStreamer installed in different prefixes?
<nekohayo> currently this machine is using the official gstreamer packages from
fedora + rpmfusion

<nekohayo> I'm wondering why those blacklisted plugins are never "re-scanned"
by gstreamer
<__tim> that's a fair question I guess. But when would one rescan them? You
don't want to do it every time. So once an hour? once a day? once a week?

<nekohayo> what if they were rescanned when apps try to access them? like when
pitivi tries to use videomixer (on top of your approach of rescanning
periodically maybe)
<__tim> interesting, maybe one could do something clever there
<__tim> ideally we'd store the reason for the blacklisting as well
<ocrete> arent they rechecked if the file changes already ?
<thaytan> the plugins are rescanned if they change
<__tim> but if they don't change ...
<thaytan> but if they failed because some underlying lib was broken and then
fixed, that's not detected
<__tim> right
<ocrete> hmm interesting point
<thaytan> storing the reason for the blacklisting is probably hard
<ocrete> also check if ld.so.cache has changed ?
<thaytan> since it's usually just 'failed to g_module_open() because of an
unresolved symbol'
<ocrete> and ignore blacklists if ld.so.cache has changed (and rescan)
<__tim> thaytan, it doesn't mention the symbol? I think it does..
<ds> if the so fails to load, there isn't much overhead trying to load every
time
<ocrete> that said, doesnt help if one use using LD_LIBRARY_PATH
<thaytan> ds: except for forking the scanner process to re-check an otherwise
clean registry
<ds> oooh, maybe recheck blacklisted plugins whenever the scanner is run, but
not run the scanner just for blacklisted plugins. Although, also mark potential
crasher blacklist plugins

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