**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 (has_metadata_in_zookeeper)
    {
        
        
        zkutil::ZooKeeperPtr zookeeper;
        if (zookeeper_name == default_zookeeper_name)
            zookeeper = getContext()->getZooKeeper();
        else
            zookeeper = getContext()->getAuxiliaryZooKeeper(zookeeper_name);
        
        if (!zookeeper)
            throw Exception("Can't drop readonly replicated table (need to drop data in ZooKeeper as well)", ErrorCodes::TABLE_IS_READ_ONLY);
        shutdown();
        dropReplica(zookeeper, zookeeper_path, replica_name, log);
    }
    dropAllData();
}
void StorageReplicatedMergeTree::dropReplica(zkutil::ZooKeeperPtr zookeeper, const String & zookeeper_path, const String & replica, Poco::Logger * logger)