**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'
```
else
    {
        
        return 0;
    }
}
void StorageReplicatedMergeTree::getReplicaDelays(time_t & out_absolute_delay, time_t & out_relative_delay)
{
    assertNotReadonly();
    time_t current_time = time(nullptr);
    out_absolute_delay = getAbsoluteDelay();
    out_relative_delay = 0;
    const auto storage_settings_ptr = getSettings();
    /** Relative delay is the maximum difference of absolute delay from any other replica,
      *  (if this replica lags behind any other live replica, or zero, otherwise).
      * Calculated only if the absolute delay is large enough.
      */
    if (out_absolute_delay < static_cast<time_t>(storage_settings_ptr->min_relative_delay_to_measure))
        return;
    auto zookeeper = getZooKeeper();
    time_t max_replicas_unprocessed_insert_time = 0;
    bool have_replica_with_nothing_unprocessed = false;
    Strings replicas = zookeeper->getChildren(fs::path(zookeeper_path) / "replicas");
    for (const auto & replica : replicas)
    {
        if (replica == replica_name)
            continue;
        
        if (!zookeeper->exists(fs::path(zookeeper_path) / "replicas" / replica / "is_active"))
            continue;