**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'
```
ReplicatedMergeTreeTableMetadata current_metadata(*this, metadata_snapshot);
            current_zookeeper->createOrUpdate(replica_path + "/metadata", current_metadata.toString(),
                zkutil::CreateMode::Persistent);
        }
        checkTableStructure(replica_path, metadata_snapshot);
        checkParts(skip_sanity_checks);
        if (current_zookeeper->exists(replica_path + "/metadata_version"))
        {
            metadata_version = parse<int>(current_zookeeper->get(replica_path + "/metadata_version"));
        }
        else
        {
            
            
            
            
            
            Coordination::Stat metadata_stat;
            current_zookeeper->get(zookeeper_path + "/metadata", &metadata_stat);
            metadata_version = metadata_stat.version;
        }
        
        
        clearOldTemporaryDirectories(0);
        clearOldWriteAheadLogs();
    }
    createNewZooKeeperNodes();
    syncPinnedPartUUIDs();
}
bool StorageReplicatedMergeTree::checkFixedGranularityInZookeeper()