**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'
```
{
    
    ReplicatedMergeTreeQueue::SelectedEntryPtr selected;
    try
    {
        selected = queue.selectEntryToProcess(merger_mutator, *this);
    }
    catch (...)
    {
        tryLogCurrentException(log, __PRETTY_FUNCTION__);
    }
    return selected;
}
bool StorageReplicatedMergeTree::processQueueEntry(ReplicatedMergeTreeQueue::SelectedEntryPtr selected_entry)
{
    LogEntryPtr & entry = selected_entry->log_entry;
    return queue.processEntry([this]{ return getZooKeeper(); }, entry, [&](LogEntryPtr & entry_to_process)
    {
        try
        {
            return executeLogEntry(*entry_to_process);
        }
        catch (const Exception & e)
        {
            if (e.code() == ErrorCodes::NO_REPLICA_HAS_PART)
            {