**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'
```
{
        LogEntry log_entry;
        if (!are_restoring_replica)
            log_entry.type = LogEntry::GET_PART;
        else
        {
            LOG_DEBUG(log, "Obtaining checksum for path {}", name);
            
            
            log_entry.type = LogEntry::ATTACH_PART;
            MinimalisticDataPartChecksums desired_checksums;
            const fs::path part_path = fs::path(source_path) / "parts" / name;
            const String part_znode = zookeeper->get(part_path);
            if (!part_znode.empty())
                desired_checksums = ReplicatedMergeTreePartHeader::fromString(part_znode).getChecksums();
            else
            {
                String desired_checksums_str = zookeeper->get(part_path / "checksums");
                desired_checksums = MinimalisticDataPartChecksums::deserializeFrom(desired_checksums_str);
            }
            const auto [lo, hi] = desired_checksums.hash_of_all_files;
            log_entry.part_checksum = getHexUIntUppercase(hi) + getHexUIntUppercase(lo);
        }
        log_entry.source_replica = "";
        log_entry.new_part_name = name;
        log_entry.create_time = tryGetPartCreateTime(zookeeper, source_path, name);
        zookeeper->create(fs::path(replica_path) / "queue/queue-", log_entry.toString(), zkutil::CreateMode::PersistentSequential);
    }
    LOG_DEBUG(log, "Queued {} parts to be fetched", active_parts.size());