**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'
```
}
            auto zookeeper = getZooKeeper();
            
            if (!zookeeper->exists(fs::path(zookeeper_path) / "replicas" / replica / "is_active"))
            {
                LOG_WARNING(log, "Replica {} is not active during mutation. Mutation will be done asynchronously when replica becomes active.", replica);
                inactive_replicas.emplace(replica);
                break;
            }
            String mutation_pointer = fs::path(zookeeper_path) / "replicas" / replica / "mutation_pointer";
            std::string mutation_pointer_value;
            
            if (!zookeeper->tryGet(mutation_pointer, mutation_pointer_value, nullptr, wait_event))
            {
                LOG_WARNING(log, "Replica {} was removed", replica);
                break;
            }
            else if (mutation_pointer_value >= mutation_id) 
                break;                                      
            
            if (wait_event->tryWait(1000))
                continue;
            
            
            auto mutation_status = queue.getIncompleteMutationsStatus(mutation_id);
            
            if (mutation_status && !mutation_status->latest_fail_reason.empty())
                break;
        }