Description Finn David 2025-03-06 12:48:05 CET

This is the follow-up to a recent import problem from one of our customers. We noticed that one of the main contributing factors was a fragmented LDAP LMDB database.

In order to prevent this from happening again, our product should:
- Check and inform administrators about this
- Provide an easy way to fix this


Upstream explanation of the issue

When a write operation is performed with LMDB, the freelist is scanned for available space to reuse if possible.  The larger the size of the freelist, the longer amount of time it will take for the operation to complete successfully. 
When the database has gotten to a certain point of fragmentation (This differs based on any individual use case), it will be start taking a noticeable amount of time for those write operations to complete and the server processing the write operation does essentially come to a halt during this process.  Once the write operation completes, things go back to normal. 
The only solution is to dump and reload the database (slapcat/slapadd or mdb_copy -c). Eventually, you will get back into the same situation and have to do this again.