**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'
```
};
        VirtualColumnUtils::filterBlockWithQuery(query_info.query, filtered_block, context);
        if (!filtered_block.rows())
            return {};
        col_database = filtered_block.getByName("database").column;
        col_table = filtered_block.getByName("table").column;
        col_engine = filtered_block.getByName("engine").column;
    }
    MutableColumns res_columns = metadata_snapshot->getSampleBlock().cloneEmptyColumns();
    for (size_t i = 0, size = col_database->size(); i < size; ++i)
    {
        StorageReplicatedMergeTree::Status status;
        dynamic_cast<StorageReplicatedMergeTree &>(
            *replicated_tables
                [(*col_database)[i].safeGet<const String &>()]
                [(*col_table)[i].safeGet<const String &>()]).getStatus(status, with_zk_fields);
        size_t col_num = 3;
        res_columns[col_num++]->insert(status.is_leader);
        res_columns[col_num++]->insert(status.can_become_leader);
        res_columns[col_num++]->insert(status.is_readonly);
        res_columns[col_num++]->insert(status.is_session_expired);
        res_columns[col_num++]->insert(status.queue.future_parts);
        res_columns[col_num++]->insert(status.parts_to_check);
        res_columns[col_num++]->insert(status.zookeeper_path);
        res_columns[col_num++]->insert(status.replica_name);
        res_columns[col_num++]->insert(status.replica_path);
        res_columns[col_num++]->insert(status.columns_version);
        res_columns[col_num++]->insert(status.queue.queue_size);
        res_columns[col_num++]->insert(status.queue.inserts_in_queue);
        res_columns[col_num++]->insert(status.queue.merges_in_queue);