**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'
```
new_part_info.mutation = mutation_version;
    String new_part_name = part.getNewName(new_part_info);
    ReplicatedMergeTreeLogEntryData entry;
    entry.type = LogEntry::MUTATE_PART;
    entry.source_replica = replica_name;
    entry.source_parts.push_back(part.name);
    entry.new_part_name = new_part_name;
    entry.new_part_uuid = new_part_uuid;
    entry.create_time = time(nullptr);
    entry.alter_version = alter_version;
    Coordination::Requests ops;
    Coordination::Responses responses;
    ops.emplace_back(zkutil::makeCreateRequest(
        fs::path(zookeeper_path) / "log/log-", entry.toString(),
        zkutil::CreateMode::PersistentSequential));
    ops.emplace_back(zkutil::makeSetRequest(
        fs::path(zookeeper_path) / "log", "", log_version)); 
    Coordination::Error code = zookeeper->tryMulti(ops, responses);
    if (code == Coordination::Error::ZBADVERSION)
    {
        ProfileEvents::increment(ProfileEvents::NotCreatedLogEntryForMutation);
        LOG_TRACE(log, "Log entry is not created for mutation {} because log was updated", new_part_name);
        return CreateMergeEntryResult::LogUpdated;
    }
    zkutil::KeeperMultiException::check(code, ops, responses);
    ProfileEvents::increment(ProfileEvents::CreatedLogEntryForMutation);
    LOG_TRACE(log, "Created log entry for mutation {}", new_part_name);
    return CreateMergeEntryResult::Ok;
}
void StorageReplicatedMergeTree::removePartFromZooKeeper(const String & part_name, Coordination::Requests & ops, bool has_children)