Improving memory usage / cache usage

[PVince81]

From @butonic:

A non exhaustive search reveals other places where an array is used to cache data:

apps/user_ldap/group_ldap.php#L46
apps/user_ldap/group_ldap.php#L51
apps/dav/lib/connector/sabre/sharesplugin.php#L67
apps/dav/lib/connector/sabre/tagsplugin.php#L80
apps/dav/lib/connector/sabre/custompropertiesbackend.php#L75
lib/private/Encryption/File.php#L35
lib/private/Files/Config/UserMountCache.php#L54
lib/private/Files/Config/UserMountCache.php#L61
lib/private/Files/Storage/LocalTempFileTrait.php#L40

We should check them after we decide how to handle this. Not all of them justify using a CappedMemoryCache, eg: lib/private/Config.php#L42

@DeepDiver1975 @rullzer @icewind1991 @schiesbn @nickvergessen

[PVince81]

More context: when running background jobs, many classes that are used might cache objects forever. This causes the memory usage to increase significantly and many cached objects aren't necessarily reused.

So one idea was to introduce the CappedCache everywhere an array is used for caching.

[rullzer]

Using a capped cache is a quickfix. But we should evaluate each change as to not break stuff when the cache is expected to hold more elements...

[nickvergessen]

I'd also say that it is just hiding other issues, but yeah, maybe we can set the size to something really huge for debug mode, so it still wastes memory for developers?

[PVince81]

From @butonic in the other ticket, itemized:

• apps/user_ldap/lib/Group_LDAP.php#L46
• apps/user_ldap/lib/Group_LDAP.php#L51
• apps/dav/lib/Connector/Sabre/SharesPlugin.php#L67
• apps/dav/lib/Connector/Sabre/TagsPlugin.php#L80
• apps/dav/lib/Connector/Sabre/CustomPropertiesBackend.php#L75
• lib/private/Encryption/File.php#L35 => Use capped cache for encryption's user access list #25055
• lib/private/Files/Config/UserMountCache.php#L54
• lib/private/Files/Config/UserMountCache.php#L61
• lib/private/Files/Storage/LocalTempFileTrait.php#L40

[PVince81]

• "$app->generateBirthdays();"

[PVince81]

@blizzz can you do the LDAP one, @icewind1991 the mount caches and FS ones, @DeepDiver1975 generateBirthdays ?

The Sabre ones are low prio because they aren't called during background jobs or updates.

[nickvergessen]

generateBirthdays is a meta one, it calls the userManager, so nothing to do there.

[PVince81]

• capped cache in user database backend: Use a CappedCache in the user database backend #24405

[butonic]

This breaks upgrades on instances with more than ~10000-15000 users