OCP/RH-SSO operator is not able to connect to the PostGreSQL database if only IPv6 interface is configured on Openshift.

1 - Infra

Openshift 4.x deployed on bare metal.
RH-SSO operator 7.63
External PostgreSQL database
IPV6 only, without IPv4 (This is only supported on bare metal).

The VM configuration option contains:
-FIPS is disabled: -Dcom.redhat.fips=false
-IPv6 only : -Djava.net.preferIPv4Stack=false -Djava.net.preferIPv6Addresses=true

Note:

Having IPv6 support only is a specificity of Openshift, when installed on bare metal.

See doc
https://docs.openshift.com/container-platform/4.13/installing/installing_with_agent_based_installer/installing-with-agent-based-installer.html#installing-ocp-agent-boot_installing-with-agent-based-installer

2. Issue description

When only IPv6 is configured keycloak-0 pod is staying in state 0/1, and Keycloak-1 is never coming up.

keycloak-0 0/1 Running 4 (76s ago) 23m
...
rhsso-operator-677d448bcb-6gs2s 1/1 Running 0 16m

Note:
When dual stack is configured (IPV4/IPv6) Pods keycloak-0 and Keycloak-1 are reaching state 1/1

3. Error message
Healthcheck probes are reporting

2362-67040- lastTimestamp: "2023-06-22T16:01:07Z"
2363-67080- message: |-
2364:67094: Readiness probe failed: {
2365-67124- "outcome" : "success",
2366-67155- "result" : [true]

Upstream tracker
https://github.com/keycloak/keycloak/issues/21277