ruby - LDAP - How to add an entry to a groupOfUniqueNames? (ERR_250_ENTRY_ALREADY_EXISTS) -

i'm trying add new member of groupofuniquenames object "entry_already_exists" error.

the server apacheds, , code ruby, using using net-ldap:

ldap.add(dn: 'cn=janitors,dc=tidy,dc=example,dc=com',           attributes:            {             :objectclass => "groupofuniquenames",             :uniquemember =>                "uid=broom001,o=users,dc=tidy,dc=example,dc=com"           } ) 

there 1 member in janitors -- mop99 . when call ldap.add, (reformatted readability):

ldap.response: err_250_entry_already_exists cn=janitors,dc=tidy,dc=example,dc=com exists! openstruct {              :code => 68,     :error_message => "entry_already_exists: failed messagetype : add_request                         message id : 2                             add request :                             entry                             dn[n]: cn=janitors,dc=tidy,dc=example,dc=com                             objectclass: groupofuniquenames                             uniquemember: uid=mop99,o=users,dc=tidy,dc=example,dc=com                             : err_250_entry_already_exists cn=janitors,dc=tidy,dc=example,dc=com exists!                       ",        :matched_dn => "",           :message => "entry exists" } 

i've tried changing ldap.add() ldap.modify(), replaces mop99 broom001, leaving 1 janitor. need add broom001, end ever-growing army of janitors.

i read existing list ldap, append new entry list in ruby, , write list ldap...but introduces race condition janitor lost when 2 try add @ same time. janitors valuable, unacceptable.

i've searched web extensively without finding much, , nothing related net-ldap. did find https://www.openldap.org/lists/openldap-software/199912/msg00164.html describes solution wrt .ldif files, don't know how translate net-ldap.

what missing?

adding object class doesn't make sense. it's there.

just add unique member value.