**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'
```
Coordination::Stat metadata_stat;
                current_zookeeper->get(zookeeper_path + "/metadata", &metadata_stat);
                metadata_version = metadata_stat.version;
            }
            catch (Coordination::Exception & e)
            {
                if (!is_first_replica && e.code == Coordination::Error::ZNONODE)
                    throw Exception("Table " + zookeeper_path + " was suddenly removed.", ErrorCodes::ALL_REPLICAS_LOST);
                else
                    throw;
            }
            if (!is_first_replica)
                createReplica(metadata_snapshot);
        }
        catch (...)
        {
            
            dropIfEmpty();
            throw;
        }
    }
    else
    {
        
        String replica_metadata;
        const bool replica_metadata_exists = current_zookeeper->tryGet(replica_path + "/metadata", replica_metadata);
        if (!replica_metadata_exists || replica_metadata.empty())
        {
            
            other_replicas_fixed_granularity = checkFixedGranularityInZookeeper();