**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 source_path = fs::path(zookeeper_path) / "replicas" / source_replica;
    
    Strings source_queue_names;
    
    
    while (true)
    {
        Coordination::Stat log_pointer_stat;
        String raw_log_pointer = zookeeper->get(fs::path(source_path) / "log_pointer", &log_pointer_stat);
        Coordination::Requests ops;
        ops.push_back(zkutil::makeSetRequest(fs::path(replica_path) / "log_pointer", raw_log_pointer, -1));
        
        if (source_is_lost_stat.version == -1)
        {
            
            
            ops.push_back(zkutil::makeCreateRequest(fs::path(source_path) / "is_lost", "0", zkutil::CreateMode::Persistent));
            ops.push_back(zkutil::makeRemoveRequest(fs::path(source_path) / "is_lost", -1));
        }
        else 
            ops.push_back(zkutil::makeCheckRequest(fs::path(source_path) / "is_lost", source_is_lost_stat.version));
        Coordination::Responses responses;