**Use case**

Currently, `system.replicas` table has `total_replicas` and `active_replicas` columns which are useful to check/alert when some replicas are down. One problem, these columns are numbers. They tell when there is a problem, but you need to further check ZooKeeper or query all the nodes to detect what exact replicas (hosts) are down/inactive/have problems.

**Describe the solution you'd like**

Add a replicas column maybe as a map which would contain the replica name, and it's status. Or, add 2 array columns with `replica_names` and `active_replica_names`

**Alternative**

Something along the line

```sql
select path, value from system.zookeeper where path IN (
    select concat(path, '/', name) from system.zookeeper where path in (select concat(zookeeper_path, '/replicas') from system.replicas)
)
and name = 'is_active'
```
String containing_part = active_parts_set.getContainingPart(missing_part);
                if (!containing_part.empty())
                    parts_to_fetch.push_back(containing_part);
                else
                    LOG_WARNING(log, "Part {} on replica {} has been vanished.", missing_part, best_replica_path);
            }
        }
        LOG_INFO(log, "Parts to fetch: {}", parts_to_fetch.size());
        missing_parts.clear();
        for (const String & part : parts_to_fetch)
        {
            bool fetched = false;
            try
            {
                fetched = fetchPart(part, metadata_snapshot, best_replica_path, true, 0, zookeeper);
            }
            catch (const DB::Exception & e)
            {
                if (e.code() != ErrorCodes::RECEIVED_ERROR_FROM_REMOTE_IO_SERVER && e.code() != ErrorCodes::RECEIVED_ERROR_TOO_MANY_REQUESTS
                    && e.code() != ErrorCodes::CANNOT_READ_ALL_DATA)
                    throw;
                LOG_INFO(log, e.displayText());
            }
            if (!fetched)
                missing_parts.push_back(part);
        }
        ++try_no;
    } while (!missing_parts.empty());
}
void StorageReplicatedMergeTree::mutate(const MutationCommands & commands, ContextPtr query_context)