Re: [keycloak-user] Is quorum needed in Keycloak Standalone Clustered Configuration?
On Thu, Aug 8, 2019 at 1:26 PM Roman Ok <warrior7089(a)gmail.com> wrote:
Sorry, i'm sending this again as my last post was posted without
text for
some unknown reason:
Should an Keycloak deployments configured in Standalone Clustered
Configuration have odd number of nodes to ensure quorum?
No, Keycloak uses Infinispan for caching and Infinispan uses JGroups for
clustering. JGroups doesn't need consensus.
It's stated that Keycloak is built on top of the WildFly application
server and its sub-projects like Infinispan (for caching) and Hibernate
(for persistence).
Keycloak recommends to look in WildFly Documentation and High Availability
Guide.
If understood correctly Standalone Clustered Configuration allows session
replication or transmission of SSO contexts around the cluster.
I don't understand though if odd number of Keycloak nodes is required so
that there will be quorum.
No it is not strictly required. As in almost all distributed systems,
having odd number of nodes helps recovering from Split Brain scenarios.
Singleton subsystem states
10.1.3. Quorum Network partitions are particularly problematic for
singleton services, since they can trigger multiple singleton providers for
the same service to run at the same time. To defend against this scenario,
a singleton policy may define a quorum that requires a minimum number of
nodes to be present before a singleton provider election can take place. A
typical deployment scenario uses a quorum of N/2 + 1, where N is the
anticipated cluster size. This value can be updated at runtime, and will
immediately affect any active singleton services. e.g.
Is it somehow related to Keycloak and its Standalone Clustered
Configuration?
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