(ITS#8852) slapd memory use grows continuously with non-delta syncrepl and modifying groups

[ryan@openldap.org]

Full_Name: Ryan Tandy
Version: 2.4.46
OS: Debian
URL: ftp://ftp.openldap.org/incoming/20180511_rtandy_syncrepl-memory-consumer.tgz
Submission from: (NULL) (70.66.128.207)
Submitted by: ryan


When running object-based syncrepl, and making changes to groups, the provider
slapd uses more and more memory, apparently without bound.

We've discussed this issue before but there was no ITS tracking it
specifically.

original Debian bug: https://bugs.debian.org/725091
and a possibly related openldap-technical post:
https://www.openldap.org/lists/openldap-technical/201503/msg00206.html

reproducer: ftp://ftp.openldap.org/incoming/20180511_rtandy_syncrepl-memory-consumer.tgz

./prepare
./runslapd (backgrounds a provider slapd and a consumer slapd)
./modify (makes a number of modifications on the provider)
./clean (kills both slapds and cleans databases)

Run top in another terminal and watch the memory growth. On my system, the
provider grows to over 3 GB resident and does not shrink even after replication
completes. with delta-syncrepl enabled, the producer's RSS is only around 10
MB.

Reproduced on Debian unstable with 2.4.46 and glibc malloc (glibc 2.27-3) and
tcmalloc_minimal (2.7-1).