code: def atlas_revalidate_peers( con=None, path=None, now=None, peer_table=None ):
      
      global MIN_PEER_HEALTH
  
      if now is None:
          now = time_now()
  
      old_peer_infos = atlasdb_get_old_peers( now, con=con, path=path )
      for old_peer_info in old_peer_infos:
          res = atlas_peer_getinfo( old_peer_info['peer_hostport'] )
          if not res:
              log.debug("Failed to revalidate %s" % (old_peer_info['peer_hostport']))
              if atlas_peer_is_whitelisted( old_peer_info['peer_hostport'], peer_table=peer_table ):
                  continue
  
              if atlas_peer_is_blacklisted( old_peer_info['peer_hostport'], peer_table=peer_table ):
                  continue
  
              if atlas_peer_get_health( old_peer_info['peer_hostport'], peer_table=peer_table ) < MIN_PEER_HEALTH:
                  atlasdb_remove_peer( old_peer_info['peer_hostport'], con=con, path=path, peer_table=peer_table )
          
          else:
              # renew 
              atlasdb_renew_peer( old_peer_info['peer_hostport'], now, con=con, path=path )
  
      return True
docs: Revalidate peers that are older than the maximum peer age.
      Ping them, and if they don't respond, remove them.