StorageUnavailableException
A store a port called could not be reached, or did not answer in time: a transient technical failure, such as a connection refused, reset or closed by a restarting server, or a connection pool or socket that timed out. The same call may succeed once the store is back.
A backend throws it, with the driver's exception as cause, from the calls that read (for the event log, every call but an append, whose outcome stays a value: me.ahoo.wow.spi.log.AppendOutcome.Unknown). Any other failure stays the driver's own exception: a defect, not something a retry fixes.
The runtime answers it as the error wow.storage.unavailable, which a caller may retry: a command with the same request id, which the kernel deduplicates, a query as it is. A store that is up but at its capacity is the subtype StorageBusyException.