Share objects across multiple containers - spring-boot

Question

We develop a spring-boot application which is deployed on OpenShift 3. The application should be scalable to at least two pods. But we use internal caches and other "global" data (some lists, some maps...) which should be the same (i.e. shared) for all the pods.
Is there a way to achieve such data sharing by a) a service, which is embedded inside the spring-boot application itself (this implies that each pod needs to find/know each other) or does it b) need in every case a standalone (potentially also scalable) cache service?
a)
|---- Application ----|
| |
| |-------------| |
| | Pod 1 | * | |
| |----------^--| |
| | |
| |----------v--| |
| | Pod 2 | * | |
| |----------^--| |
| | |
| |----------v--| |
| | Pod n | * | |
| |-------------| |
| |
|----------------------
* "embedded cache service"
b)
|---- Application ----|
| |
| |-------------| |
| | Pod 1 | |-----\
| |-------------| | \
| | | \
| |-------------| | \ |-----------------------|
| | Pod 2 | |-----------| Cache Service/Cluster |
| |-------------| | / |-----------------------|
| | | /
| |-------------| | /
| | Pod n | |------/
| |-------------| |
| |
|----------------------
Typically, if we would use memcached or redis I think b) would be the only solution. But how is it with Hazlecast?

Answer 1

With Hazelcast, you can both use a & b.
For scenario a, assuming you're using k8s on OpenShift, you can use Hazelcast Kubernetes discovery plugin so that pods deployed in the same k8s cluster discover themselves & form a cluster: https://github.com/hazelcast/hazelcast-kubernetes
For scenario b, Hazelcast has an OpenShift image as well, which requires an Enterprise subscription: https://github.com/hazelcast/hazelcast-openshift. If you need open-source version, you can use Hazelcast Helm Chart to deploy data cluster separately: https://github.com/helm/charts/tree/master/stable/hazelcast