Function get_streaming_stats

pub async fn get_streaming_stats(
    __arg0: Extension<Service>,
) -> Result<Json<GetStreamingStatsResponse>, DashboardError>

NOTE(kwannoel): Although we fetch the BP for the entire graph via this API, the workload should be reasonable. In most cases, we can safely assume each node has most 2 outgoing edges (e.g. join). In such a scenario, the number of edges is linear to the number of nodes. So the workload is proportional to the relation id graph we fetch in get_relation_id_infos.