As discussed in
HDFS-11535, this JIRA adds a new function combining both the new and the old chooseRandom methods for better performance.
More specifically, when choosing a random node with storage type requirement, the combined method first tries the old method of blindly picking a random node. If this node satisfies, it is returned. Otherwise, the new chooseRandom is called, which guarantees to find a eligible node in one call (if there is one at all).