**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'
```
exists_futures.emplace_back(zookeeper->asyncExists(part_path));
    }
    std::vector<std::future<Coordination::MultiResponse>> enqueue_futures;
    enqueue_futures.reserve(parts_to_fetch.size());
    for (size_t i = 0; i < parts_to_fetch.size(); ++i)
    {
        const String & part_name = parts_to_fetch[i];
        Coordination::Requests ops;
        String has_replica = findReplicaHavingPart(part_name, true);
        if (!has_replica.empty())
        {
            LOG_ERROR(log, "Removing locally missing part from ZooKeeper and queueing a fetch: {}", part_name);
            time_t part_create_time = 0;
            Coordination::ExistsResponse exists_resp = exists_futures[i].get();
            if (exists_resp.error == Coordination::Error::ZOK)
            {
                part_create_time = exists_resp.stat.ctime / 1000;
                removePartFromZooKeeper(part_name, ops, exists_resp.stat.numChildren > 0);
            }
            LogEntry log_entry;
            log_entry.type = LogEntry::GET_PART;
            log_entry.source_replica = "";
            log_entry.new_part_name = part_name;
            log_entry.create_time = part_create_time;
            
            ops.emplace_back(zkutil::makeCreateRequest(
                fs::path(replica_path) / "queue/queue-", log_entry.toString(), zkutil::CreateMode::PersistentSequential));
            enqueue_futures.emplace_back(zookeeper->asyncMulti(ops));
        }
        else