**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 source_is_lost_stat;
    size_t future_num = 0;
    for (const String & source_replica_name : replicas)
    {
        if (source_replica_name == replica_name)
            continue;
        auto get_is_lost     = futures[future_num++].get();
        auto get_log_pointer = futures[future_num++].get();
        auto get_queue       = futures[future_num++].get();
        if (get_is_lost.error != Coordination::Error::ZOK)
        {
            LOG_INFO(log, "Not cloning {}, cannot get '/is_lost': {}", source_replica_name, Coordination::errorMessage(get_is_lost.error));
            continue;
        }
        else if (get_is_lost.data != "0")
        {
            LOG_INFO(log, "Not cloning {}, it's lost", source_replica_name);
            continue;
        }
        if (get_log_pointer.error != Coordination::Error::ZOK)
        {
            LOG_INFO(log, "Not cloning {}, cannot get '/log_pointer': {}", source_replica_name, Coordination::errorMessage(get_log_pointer.error));
            continue;
        }
        if (get_queue.error != Coordination::Error::ZOK)
        {
            LOG_INFO(log, "Not cloning {}, cannot get '/queue': {}", source_replica_name, Coordination::errorMessage(get_queue.error));
            continue;
        }