I’ve encountered a bug with paged queries to a front end (“directory proxy”) Oracle Unified Directory server. When the load balancing algorithm is configured to distribute traffic equally across the back-end servers (proportional distribution algorithm), some queries return duplicate records. Not quite an infinite loop — for a small-ish (like 1300 objects) record set, I usually reach the end of the returned data round 50k records. But certainly not a valid result set either. And for a large result set (like 13,000 objects), it seems endless.

The oddest thing, though, is that different filters which produce the same result set do not all return duplicate results. Our uid values are algorithmically formed — those with employeeType of RealEmployee all start with ‘A’, those with employeeType of Contractor all start with ‘B’ type of rule. The prefix is then followed by a numeric sequence number. The filter (&(!(uid=A*)(uid=B*))(sn=*)) duplicates results and seemingly runs forever. The filter (&((employeeType=RealEmployee)(employeeType=Contractor))(sn=*)) returns the ~11k expected results. Go figure. Although this is algorithmically quite odd, it does provide a nice work-around to the bug as I just had to try different filters until I found one that produced non-duplicated results.