Ship BerkleyDB backend as a module

Summary

Change the openldap-servers package so that BDB and HDB backends are required to be dynamically loaded.

Owner

Name: Simon Pichugin
Email: spichugi (at) redhat (dot) com

Current status

Targeted release: Fedora 35
Last updated: 2021-02-10
Tracker bug: #1740811
Release notes tracker: #377

Detailed Description

So far the BDB and HDB were statically built with the slapd binary and merely declaring database bdb or database hdb would just work. Change introduces an additional requirement of explicitly declaring to load the backend's SO file according to the documentation of dynamic modules. The respective new modules will be shipped similarly to the rest of the already shipped modules.

This change is directed to conduct a smoother experience before the backends are removed in a next Fedora release. Current configurations using BDB or HDB backend would break, however are easily fixable by a single change; this is intentional as due to the upcoming removal of these backends users should be aware of the necessity to migrate to a different backend in a near future (see #User Experience for more).

Benefit to Fedora

A step on a way to remove unsupported (both by OpenLDAP and BerkleyDB upstream) piece of software.

Scope

Proposal owners:

Change the SPEC file accordingly.

Other developers: N/A (not a System Wide Change)

Release engineering: #Releng issue number (a check of an impact with Release Engineering is needed)

Policies and guidelines: N/A (not a System Wide Change)

Trademark approval: N/A (not needed for this Change)

Upgrade/compatibility impact

Server using BDB or HDB backends without modified configuration would fail to start. See User Experience section for more information.

How To Test

N/A (not a System Wide Change)

User Experience

To remediate the impact of the change the systemd service file shipped with the package will contain a pre-start script which, in case the server is configured with BDB or HDB backend, will halt the startup and notify the user with a message describing what and why happened, and what steps to take to mitigate the issue.

If a user is using either BDB or HDB they have two options:

migrate to the fully supported MDB backend (preferred)
add a moduleload configuration declaration (discouraged)

Migrating to MDB

The steps required to migrate a database are following:

Stop the slapd server.
Export data to an LDIF file using slapcat.
Change the server's configuration replacing the BDB/HDB sections with its MDB counterparts.
Import data to a new database from the LDIF file using slapadd.
Start the slapd server.

ModuleLoad the BDB/HDB backend

Depending on the configuration style and backend type, user should add a declaration in order to load the backend library: add option moduleload (slapd.conf(5), section GLOBAL CONFIGURATION OPTIONS) or attribute olcModuleLoad (slapd-config(5), section DYNAMIC MODULE OPTIONS) with value back_bdb and/or back_hdb.

Dependencies

None.

Contingency Plan

Contingency mechanism: Revert the change.
Contingency deadline: Anytime.
Blocks release? No.
Blocks product? None.

Documentation