@Override
    public String toString() {
      return "[" + fullName + ", query parallelism " + queryParallelism
        + ", fraction of the cluster " + finalFraction + ", fraction used by child pools "
        + (finalFraction - finalFractionRemaining) + ", active sessions " + sessions.size()
        + ", initializing sessions " + initializingSessions.size() + "]";
    }
State of a single pool.
Unless otherwise specified, the members are only modified by the master thread.
ql/src/java/org/apache/hadoop/hive/ql/exec/tez/WorkloadManager.java