**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'
```
{
    if (zookeeper->expired())
        throw Exception("Table was not dropped because ZooKeeper session has expired.", ErrorCodes::TABLE_WAS_NOT_DROPPED);
    auto remote_replica_path = zookeeper_path + "/replicas/" + replica;
    LOG_INFO(logger, "Removing replica {}, marking it as lost", remote_replica_path);
    
    
    zookeeper->trySet(zookeeper_path + "/replicas/" + replica + "/is_lost", "1");
    
    zookeeper->tryRemoveRecursive(remote_replica_path);
    if (zookeeper->exists(remote_replica_path))
        LOG_ERROR(logger, "Replica was not completely removed from ZooKeeper, {} still exists and may contain some garbage.", remote_replica_path);
    
    Strings replicas;
    if (Coordination::Error::ZOK != zookeeper->tryGetChildren(zookeeper_path + "/replicas", replicas) || !replicas.empty())
        return;
    LOG_INFO(logger, "{} is the last replica, will remove table", remote_replica_path);
    /** At this moment, another replica can be created and we cannot remove the table.
      * Try to remove /replicas node first. If we successfully removed it,
      * it guarantees that we are the only replica that proceed to remove the table
      * and no new replicas can be created after that moment (it requires the existence of /replicas node).
      * and table cannot be recreated with new /replicas node on another servers while we are removing data,
      * because table creation is executed in single transaction that will conflict with remaining nodes.
      */