**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'
```
extern const int TOO_MANY_FETCHES;
    extern const int BAD_DATA_PART_NAME;
    extern const int PART_IS_TEMPORARILY_LOCKED;
    extern const int CANNOT_ASSIGN_OPTIMIZE;
    extern const int KEEPER_EXCEPTION;
    extern const int ALL_REPLICAS_LOST;
    extern const int REPLICA_STATUS_CHANGED;
    extern const int CANNOT_ASSIGN_ALTER;
    extern const int DIRECTORY_ALREADY_EXISTS;
    extern const int ILLEGAL_TYPE_OF_ARGUMENT;
    extern const int UNKNOWN_POLICY;
    extern const int NO_SUCH_DATA_PART;
    extern const int INTERSERVER_SCHEME_DOESNT_MATCH;
    extern const int DUPLICATE_DATA_PART;
    extern const int BAD_ARGUMENTS;
    extern const int CONCURRENT_ACCESS_NOT_SUPPORTED;
}
namespace ActionLocks
{
    extern const StorageActionBlockType PartsMerge;
    extern const StorageActionBlockType PartsFetch;
    extern const StorageActionBlockType PartsSend;
    extern const StorageActionBlockType ReplicationQueue;
    extern const StorageActionBlockType PartsTTLMerge;
    extern const StorageActionBlockType PartsMove;
}
static const auto QUEUE_UPDATE_ERROR_SLEEP_MS        = 1 * 1000;
static const auto MUTATIONS_FINALIZING_SLEEP_MS      = 1 * 1000;
static const auto MUTATIONS_FINALIZING_IDLE_SLEEP_MS = 5 * 1000;
void StorageReplicatedMergeTree::setZooKeeper()