**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();
    String metadata_str = zookeeper->get(zookeeper_path + "/metadata");
    auto metadata_from_zk = ReplicatedMergeTreeTableMetadata::parse(metadata_str);
    return metadata_from_zk.index_granularity_bytes == 0;
}
void StorageReplicatedMergeTree::waitMutationToFinishOnReplicas(
    const Strings & replicas, const String & mutation_id) const
{
    if (replicas.empty())
        return;
    std::set<String> inactive_replicas;
    for (const String & replica : replicas)
    {
        LOG_DEBUG(log, "Waiting for {} to apply mutation {}", replica, mutation_id);
        zkutil::EventPtr wait_event = std::make_shared<Poco::Event>();
        while (!partial_shutdown_called)
        {
            
            
            Coordination::Stat exists_stat;
            if (!getZooKeeper()->exists(fs::path(zookeeper_path) / "mutations" / mutation_id, &exists_stat, wait_event))
            {
                throw Exception(ErrorCodes::UNFINISHED, "Mutation {} was killed, manually removed or table was dropped", mutation_id);