[Koha-bugs] [Bug 31074] Cached plugin code is used in Koha even after changes to plugin (install/upgrade/uninstall)

[bugzilla-daemon at bugs.koha-community.org]

https://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=31074

--- Comment #19 from David Cook <dcook at prosentient.com.au> ---
(In reply to Olivier Hubert from comment #16)
> Note that I was unable to recreate the potential issue with only one worker
> seeing the changes once Module::Refresh does its job.

I just reproduced the problem on my first try with a standard
koha-testing-docker setup with 2 starman workers:

[2023/06/19 06:17:49] [WARN] It's a good thing you double-checked this plugin
before installing it. 0.0.4 28969 at
/var/lib/koha/kohadev/plugins/Koha/Plugin/Prosentient/NoisyPlugin.pm line 48.
[2023/06/19 06:17:49] [WARN] You did check this plugin before installing it,
right? 0.0.4 28969 at
/var/lib/koha/kohadev/plugins/Koha/Plugin/Prosentient/NoisyPlugin.pm line 50.

[2023/06/19 06:17:53] [WARN] It's a good thing you double-checked this plugin
before installing it. 0.0.3 at
/var/lib/koha/kohadev/plugins/Koha/Plugin/Prosentient/NoisyPlugin.pm line 48.
[2023/06/19 06:17:53] [WARN] You did check this plugin before installing it,
right? 0.0.3 at
/var/lib/koha/kohadev/plugins/Koha/Plugin/Prosentient/NoisyPlugin.pm line 50.

[2023/06/19 06:18:11] [WARN] It's a good thing you double-checked this plugin
before installing it. 0.0.4 28969 at
/var/lib/koha/kohadev/plugins/Koha/Plugin/Prosentient/NoisyPlugin.pm line 48.
[2023/06/19 06:18:11] [WARN] You did check this plugin before installing it,
right? 0.0.4 28969 at
/var/lib/koha/kohadev/plugins/Koha/Plugin/Prosentient/NoisyPlugin.pm line 50.

[2023/06/19 06:18:13] [WARN] It's a good thing you double-checked this plugin
before installing it. 0.0.3 at
/var/lib/koha/kohadev/plugins/Koha/Plugin/Prosentient/NoisyPlugin.pm line 48.
[2023/06/19 06:18:13] [WARN] You did check this plugin before installing it,
right? 0.0.3 at
/var/lib/koha/kohadev/plugins/Koha/Plugin/Prosentient/NoisyPlugin.pm line 50.

[2023/06/19 06:18:15] [WARN] It's a good thing you double-checked this plugin
before installing it. 0.0.4 28969 at
/var/lib/koha/kohadev/plugins/Koha/Plugin/Prosentient/NoisyPlugin.pm line 48.
[2023/06/19 06:18:15] [WARN] You did check this plugin before installing it,
right? 0.0.4 28969 at
/var/lib/koha/kohadev/plugins/Koha/Plugin/Prosentient/NoisyPlugin.pm line 50.

The lines with 0.0.4 28969 are the one that was refreshed using the
Module::Refresh patch, and the lines with 0.0.3 are the 2nd Plack worker which
didn't get refreshed, since Module::Refresh didn't run in that process. 

> Moving forward, if forcing a Plack refresh is not the way to go then I am
> unsure of the best approach. It seems to me like reading the plugin's main
> file on every use defeats the purpose of using Plack. Which is why I focused
> on doing it only when installing / upgrading.

There are ways...

1.
In the "plugin_data" table, we have __INSTALLED_VERSION__.

During get_enabled_plugins() and GetPlugins() and Koha::Plugins::Handler->run,
and probably other places..., we can compare $class->{metadata}->{version}
against __INSTALLED_VERSION__ (note this is a class lookup and not an object
lookup, so it would be called before calling the new() constructor to create an
object). You could fetch all values for the key __INSTALLED_VERSION__ in 1
database call to reduce overhead. 

(As for reading the plugin's main file on every use - the file is already
loaded into the process's memory. So the plugin's coded information is already
available.)

2. 
A Debian package friendly solution could be running
"kill('HUP',$starman_master_pid);" after installing/upgrading a plugin. 

I talk about this at
https://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=30897#c1

It's a bit of a nuclear option but it would be the cleanest.

3.
We could do a Plack middleware, although that would run for every single web
request. That's probably not necessary.

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