[HBASE-22009] Improve RSGroupInfoManagerImpl#getDefaultServers()

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 3.0.0-alpha-1, 1.5.0, 2.2.0
• Component/s: rsgroup
• Assignee: Xiang Li
• Reporter: Xiang Li
• Created: 07/Mar/19 16:05
• Updated: 28/Apr/19 00:55
• Resolved: 22/Mar/19 07:06

Description

RSGroupInfoManagerImpl.java

private SortedSet<Address> getDefaultServers() throws IOException {
  SortedSet<Address> defaultServers = Sets.newTreeSet();
  for (ServerName serverName : getOnlineRS()) {
    Address server = Address.fromParts(serverName.getHostname(), serverName.getPort());
    boolean found = false;
    for (RSGroupInfo rsgi : listRSGroups()) {
      if (!RSGroupInfo.DEFAULT_GROUP.equals(rsgi.getName()) && rsgi.containsServer(server)) {
        found = true;
        break;
      }
    }
    if (!found) {
      defaultServers.add(server);
    }
  }
  return defaultServers;
}

That is a logic of 2 nested loops. And for each server, listRSGroups() allocates a new LinkedList and calls Map#values(), both of which are very heavy operations.

Maybe the inner loop could be moved out, that is

1. Build a list of servers of other groups than default group
2. Iterate each online servers and check if it is in the list above. If it is not, then it belongs to default group.