Function apply_compensation

nodedb-cluster/src/metadata_group/cache.rs:219–260

(
    routing: Option<&std::sync::Arc<std::sync::RwLock<RoutingTable>>>,
    step: usize,
    migration_id: uuid::Uuid,
    comp: &Compensation,
)

}

fn apply_compensation(
    routing: Option<&std::sync::Arc<std::sync::RwLock<RoutingTable>>>,
    step: usize,
    migration_id: uuid::Uuid,
    comp: &Compensation,
) -> Result<(), ClusterError> {
    let Some(live) = routing else {
        // No routing handle attached — log and treat as success.
        // This path is only reachable in unit tests without live state.
        debug!(
            migration_id = %migration_id,
            step,
            ?comp,
            "compensation: no live routing handle, skipping"
        );
        return Ok(());
    };

    let mut rt = live.write().unwrap_or_else(|p| p.into_inner());
    match comp {
        Compensation::RemoveLearner { group_id, peer_id }
        | Compensation::RemoveVoter { group_id, peer_id } => {
            rt.remove_group_member(*group_id, *peer_id);
        }
        Compensation::RestoreLeaderHint { group_id, peer_id } => {
            rt.set_leader(*group_id, *peer_id);
        }
        Compensation::RemoveGhostStub { vshard_id: _ } => {
            // Ghost stub removal is handled by the caller's ghost_table;
            // the routing table has no ghost state.
        }
    }
    drop(rt);

    debug!(
        migration_id = %migration_id,
        step,
        ?comp,
        "compensation applied"
    );
    Ok(())
}