Major Description
org.apache.hadoop.gateway.ha.provider.impl.DefaultURLManager is not thread-safe.
Currently, only the "write" methods are subject to locking. Apparently, there are some assumptions being made about the behavior of the underlying ConcurrentLinkedQueue.
For instance, if a thread is preempted in setActiveURL(String), and another thread invokes getActiveURL(), the urls.peek() result could be incorrect.