[keycloak-dev] Potential performance regression between 3.4.3.Final and 4.3.0.Final

[Thomas Darimont]

Hello Keycloak team,

has anyone encountered some performance issues after upgrading 3.4.3 to 4.x
(4.3.0)?

Today I noticed a performance regression while preparing an upgrade
from Keycloak 3.4.3.Final to 4.3.0.Final in our staging environment.

In our test environment, we have around ~100k test users stored in a
postgres-backed database. When we started the server with the new Keycloak
version, the migration went through, and everything looked fine at first,
but when we tried to browse the list of users via the admin-console, we
noticed that the CPU and memory consumption of the server increased
significantly, up to a point where Keycloak crashed with an OOME.

All previous Keycloak versions including 3.4.3 were very modest with their
memory requirements and quite happy with ~1g heap.
However, that seems to have changed in Keycloak 4.3.0 - there we needed at
least 4g to prevent Keycloak from crashing with an OOME.
Furthermore, we noticed that the response times for browsing the paginated
user view increased significantly as well:
In Keycloak 3.4.3 the average time to load a user page is ~80ms. In
Keycloak 4.3.0 (and older versions >= 4.0.0.Beta1) the same operation takes
~7 seconds for a test realm with just 10k users.

In the test realm with 100k users, the time to load a single page in the
users listing was 66 seconds for version 4.3.0, on average - compared to
quite stable 80ms in 3.4.3.

The database query that is executed by Keycloak 4.3.0 runs in ~1.5 seconds
for 100k users, so I assume the processing logic in Keycloak is the culprit.

The problem of long load-times can be reproduced with the Keycloak docker
images and the in-memory database. I also created a small example project
that creates some users with just a few attributes in a docker based 3.4.3
and 4.3.0 Keycloak environment with a Postgres database to reproduce the
problem.
https://github.com/thomasdarimont/kc-user-regression-tester

Cheers,
Thomas