High Availability & Elasticity
Infinispan automatically distributes data across cluster nodes and rebalances when the topology changes. Add nodes to scale out, remove them to scale in — data movement happens transparently with zero downtime.
Clustering modes
Distributed mode — data is spread across the cluster with a configurable number of copies (owners). With 2 owners, the cluster tolerates any single node failure without data loss. Scales to hundreds of nodes.
Replicated mode — every node holds a full copy of all data. Maximum read throughput (any node can serve any request) at the cost of write amplification. Best for small, read-heavy datasets.
Invalidation mode — each node maintains its own local cache. When one node updates an entry, it invalidates copies on other nodes. Minimizes network traffic when writes are infrequent.
What happens when a node fails?
- The cluster detects the missing node (configurable timeout, typically seconds).
- Surviving nodes that hold backup copies promote them to primary.
- New backup copies are created on other nodes to restore the configured redundancy level.
- HotRod clients detect the topology change automatically and route requests to the new data owners.
No manual intervention required. No data loss. No downtime.
Elastic scaling
Add a node to an existing cluster:
- The new node joins via auto-discovery (UDP multicast, DNS, Kubernetes API, or JDBC).
- The cluster rebalances — existing nodes transfer segments to the new member.
- Once rebalancing completes, the new node serves reads and writes.
Remove a node (planned or unplanned) and the same rebalancing runs in reverse.
Session externalization
A popular use for Infinispan is as a shared store for stateful data. Applications externalize HTTP sessions to Infinispan clusters, staying lightweight and stateless while Infinispan handles:
- Replication — sessions survive application restarts and node failures.
- Expiration — idle sessions are cleaned up automatically with TTL.
- Scalability — add application instances without session affinity (sticky sessions).
