Snapshot Caching

The component responsible for storing and managing snapshots is called the SnapshotCache.

Factus does not provide a default SnapshotCache, requiring users to make an explicit configuration choice. If a SnapshotCache is not configured, any attempt to use snapshots will result in an UnsupportedOperationException.

By default, the SnapshotCache retains only the latest version of a particular snapshot.

There are several predefined SnapshotCache implementations available, with plans to introduce additional options in the future.

In-Memory SnapshotCache

For scenarios where persistence and sharing of snapshots are not necessary, and sufficient RAM is available, the in-memory solution can be used:

<dependency>
    <groupId>org.factcast</groupId>
    <artifactId>factcast-snapshotcache-local-memory</artifactId>
</dependency>

Refer to the In-Memory Properties for configuration details.

In-Memory and Disk SnapshotCache

To persist snapshots on disk, consider using the following configuration:

<dependency>
    <groupId>org.factcast</groupId>
    <artifactId>factcast-snapshotcache-local-disk</artifactId>
</dependency>

Note that this setup is designed for single-instance applications and handles file access synchronization within the active instance. It is not recommended for distributed application architectures.

Refer to the In-Memory and Disk Properties for more information.

Redis SnapshotCache

For applications utilizing Redis, the Redis-based SnapshotCache offers an optimal solution:

<dependency>
    <groupId>org.factcast</groupId>
    <artifactId>factcast-snapshotcache-redisson</artifactId>
</dependency>

This option supports multiple instances of the same application, making it suitable for distributed environments. By default, this cache automatically deletes stale snapshots after 90 days.

For further details, see the Redis Properties.