**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'
```
IMergeTreeDataPart::TTLInfos ttl_infos;
    size_t max_volume_index = 0;
    for (auto & part_ptr : parts)
    {
        ttl_infos.update(part_ptr->ttl_infos);
        max_volume_index = std::max(max_volume_index, getStoragePolicy()->getVolumeIndexByDisk(part_ptr->volume->getDisk()));
    }
    auto table_lock = lockForShare(RWLockImpl::NO_QUERY, storage_settings_ptr->lock_acquire_timeout_for_background_operations);
    StorageMetadataPtr metadata_snapshot = getInMemoryMetadataPtr();
    FutureMergedMutatedPart future_merged_part(parts, entry.new_part_type);
    if (future_merged_part.name != entry.new_part_name)
    {
        throw Exception("Future merged part name " + backQuote(future_merged_part.name) + " differs from part name in log entry: "
            + backQuote(entry.new_part_name), ErrorCodes::BAD_DATA_PART_NAME);
    }
    std::optional<CurrentlySubmergingEmergingTagger> tagger;
    ReservationPtr reserved_space = balancedReservation(
        metadata_snapshot,
        estimated_space_for_merge,
        max_volume_index,
        future_merged_part.name,
        future_merged_part.part_info,
        future_merged_part.parts,
        &tagger,
        &ttl_infos);
    if (!reserved_space)
        reserved_space
            = reserveSpacePreferringTTLRules(metadata_snapshot, estimated_space_for_merge, ttl_infos, time(nullptr), max_volume_index);
    future_merged_part.uuid = entry.new_part_uuid;