Persistence

UniCore's persistence layer is responsible for storing and retrieving the system's state and events. The following errors may be encountered during persistence operations:

Aggregate Conflict

This error is raised when a command is rejected due to an aggregate conflict, often caused by optimistic locking failures or concurrent modifications. The system returns a 503 Service Unavailable error, indicating that the server is temporarily unable to process the request—possibly due to overload.

Resolution

Retry the operation after a brief wait. If the problem persists, investigate system load and database performance to address potential concurrency or performance issues.

Database Connection Error

This error occurs when the system is unable to establish a connection with the database during persistence operations. It can be caused by network issues, misconfigured database settings, or downtime on the database server.

Resolution

Verify the database connection settings and ensure that the database server is operational. Consult system logs for additional details to diagnose and resolve connection issues.

Deserialization Error

This error is raised when the system fails to deserialize events from the event store. Typically, this occurs due to a schema mismatch—often resulting from changes in the event format without supporting data migration.

Resolution

Because data migration is currently not supported in UniCore, the only resolution is to reset the event store by wiping the existing data.