enh(metadata): Introduce a memory limit for metadata generation

[solracsf]

Summary

Fix https://github.com/nextcloud/server/issues/42793

By introducing a (configurable) memory limit, one should not reach OOM on very big files that the server can't support.

TODO

• [x] Once approved, document metadata_max_filesize param

Similar to:

https://github.com/nextcloud/server/blob/265e9060f87b4865485e0852724b0a2b398e0b6d/config/config.sample.php#L1241-L1249

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• [ ] Tests (unit, integration, api and/or acceptance) are included
• [ ] Screenshots before/after for front-end changes
• [x] Documentation (manuals or wiki) has been updated or is not required
• [x] Backports requested where applicable (ex: critical bugfixes)

[solracsf]

Suggestion: Add the new parameter to config.sample.php here too

It's the ToDo point on the PR summary 😉

[kesselb]

Thank you, good idea :+1:

I think the decision "can this file be processed" should live in the actual event listeners. But the event listeners I checked all read the file, and therefore it's a practical approach.

The naming is a bit misleading because it's not a memory limit but a file size limit.

[solracsf]

The naming is a bit misleading because it's not a memory limit but a file size limit.

If metadata_max_filesize fits best please let me know.

[kesselb]

The naming is a bit misleading because it's not a memory limit but a file size limit.

If metadata_max_filesize fits best please let me know.

That's good, thank you :+1:

[kesselb]

Please don't forget to update the config.sample.php

I'm not sure how useful the debug log is, but without you have no idea why the metadata generation was skipped for a given file.

[st3iny]

/backport to stable29

[kesselb]

Psalm is failing because the latest rebase brought in https://github.com/nextcloud/server/pull/46450 that changed IConfig to IAppConfig.