Todo: Invalidate cache of webresource

[jensens]

As discussed with @pbauer and @MrTango

• provide utility function in resources.utils.bundles_changed to write timestamp (int) at Plone root to _webresources_bundle_changed.
• add value of _webresources_bundle_changed to cache hash of rendered resource viewlet
• add subscriber to plone.registry record lifecycle events and call above function if a prefix plone.bundle... changes.
• if in theme a "clear cache" is requested, call above function.

[mauritsvanrees]

I like it.
Thise timestamp could also be used as value of the resourceRegistries etag.

[jensens]

• if in theme a "clear cache" is requested, call above function.

Probably it is better if there (if there isn't already) is a event in plone.app.theming to subscribe to. Otherwise we may introduce circular dependencies...

[jensens]

In Resource Registry Control Panel we have the possibility to go to debug mode and back. I think this is no longer needed. Correct me if I am wrong (or re-open)

[MrTango]

What does that back and forth do for cache invalidation?

[jensens]

the hash is calcultated again, so a new url is used if the referenced file changed.

[fredvd]

@jensens How has the cache invalidation now been implemented? I checked Products.CMFPlone /resources but I cannot find anything that looks like "bundles_changed" or bundle_changed or how the cache works.

[jensens]

@fredvd The UniqueResourceTraverser ++webresource++SOMETHING is registered w/o any specific functionality except it inserts the HASH to the URL. Hash calculation and URL generation is performed by webresource itself from the given file. If the file changes, the hash changes, so the generated URL changes. Invalidation happens automatically. The development settings are only controlling the caching of the whole rendered viewlet, since rendering can be expensive due to hash calculation.

[mauritsvanrees]

@jensens What I am seeing now, is that in production mode the scripts and styles viewlets are cached in volatile attributes on the site root, and are not changed until a restart, or until you enable and disable debug mode.

So what happens when you install an add-on with an extra bundle? Nothing:

• Install plone.session.
• No extra style link is added in the viewlet.
• Click debug mode.
• Bingo, the extra style is there.

I don't know if this is what you meant yourself when creating this issue. :-)

It would be nice if this worked without a Manager needing to remember to do this. In Plone 5.2 we had an import step for this, that checked if registry.xml contained changes to the resource registries, and then combined bundles, or whatever it did. Maybe something similar could be done in Plone 6?

[jensens]

in production mode the scripts and styles viewlets are cached in volatile attributes on the site root, and are not changed until a restart, or until you enable and disable debug mode.

That is the idea of "production".

So what happens when you install an add-on with an extra bundle? Nothing.

Indeed.

I don't know if this is what you meant yourself when creating this issue. :-)

probably - and I could have forgotten about that. Not that the old resource registry was better here, but we can do better.

So I reopen and put it on the 6.1 list.

[mauritsvanrees]

I think solving this would be a bugfix and does not need to wait until 6.1. It does need careful consideration though.

I have created PR #3771.

[yurj]

My idea: #3771 (comment)