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feat: locally cache frequently requested LDAP mapping data - #54429
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come-nc
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I tend to be a bit scared about this kind of things, we cache stuff from LDAP to DB to avoid too many LDAP queries, and then we cache stuff from DB to Cache to avoid DB queries.
Why local cache and not distributed? Is it because the cache is local that there is the FIXME about broadcasting?
Why the limit to 2000 by default, what is the risk of putting too much lines in Cache? 1MiB does not sound like that much.
| /** @var array caches Names (value) by DN (key) */ | ||
| protected $cache = []; | ||
| protected function initLocalCache(): void { | ||
| if ($this->isCLI || !$this->cacheFactory->isLocalCacheAvailable()) { |
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For APCu does not have a shared cache. There is no benefit over the runtime cache that was already present.
| return; | ||
| } | ||
| $section = \str_contains($this->getTableName(), 'user') ? 'u/' : 'g/'; |
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| $section = \str_contains($this->getTableName(), 'user') ? 'u/' : 'g/'; | |
| $section = $this->getTableName(); |
Why make it more complicated than this?
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Why make it more complicated than this?
It is shorter and thus may save allocation of bytes in APCU.
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It showed that 5% of our queries are just those lookups. UPDATE looking at current data it is 7% of all queries that are
Local cache is faster, and does not require any networking. There is also no global state here, but data that barely changes (and for that we have logic already).
When APCu overflows, then the entire cache is flushed, which then is quite expensive across the whole instance. |
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Oct 15, 2025
/backport to stable32 |
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artonge
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Looks good to me besides nitpick
Does it mean that admin would need to flush the cache if they change one user's display name? If so, we'll need to update the documentation.
| return; | ||
| } | ||
| $useLocalCache = $this->config->getValueString('user_ldap', 'use_local_mapping_cache', 'auto', false); |
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👍 I'll check. I saw lexicon flying by, but don't really know what it does yet.
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From a first glance, I suppose Lexicon support would be a follow-PR as we have other switches as well.
blizzz
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Oct 16, 2025
No, this is unrelated to the display name. It only stores DNs to a userid, or false if there is none (e.g. local users are thrown against this through the user abstraction layer on userExists calls). |
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Signed-off-by: Arthur Schiwon <blizzz@arthur-schiwon.de>
- has the advantage that queries will be reported in the query.log when configured Signed-off-by: Arthur Schiwon <blizzz@arthur-schiwon.de>
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Oct 17, 2025
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Summary
We save that looking up DN by user/group ID is taking up to 5% of all database queries. Albeit they are simple and do not transfer much data, it is still worthwhile to reduce them, since this data barely ever changes.
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