why UserGroupInformation equals method depend on the subject object

[Wangwenli]

Hi all,

      my question is    why UserGroupInformation equals method depend on the 
subject object?


       try below code which is extract from HiveMetaStore:

UserGroupInformation clientUgi = null;
UserGroupInformation clientUgi2 = null;
try {
clientUgi = UserGroupInformation.createProxyUser("user2", 
UserGroupInformation.getLoginUser());
clientUgi2 = UserGroupInformation.createProxyUser("user2", 
UserGroupInformation.getLoginUser());
if (clientUgi.equals(clientUgi2)) {
System.out.println("==");
} else {
System.out.println("!=");           //  strangely  this will be hit
}
} catch (IOException e1) {
e1.printStackTrace();
}

      i found that it is because the equal method from UserGroupInformation is 
compare on subject object ref : subject == ((UserGroupInformation) o).subject;  
.

     as you know,   ipc.Client connect to namenode,   
connections.get(ConnectionId)    this code will try to reuse the same socket to 
namenode, but because of ConnectionId's equal depend on ugi equal, which will 
cause connections.get(ConnectionId) cann't get the same socket,   suppose many 
connect to HiveMetaStore, then many connection to Namenode will established.

      so my doubts is why UserGroupInformation is compare on subject object ref 
: subject == ((UserGroupInformation) o).subject,   it should compare on 
subject's principal,  am i right?





________________________________
wenli
Regards