private final void fillBulker() {
        while (this.traversal.hasNext() && this.bulker.size() < this.barrierSize) {
            this.bulker.add(this.traversal.nextTraverser());
        }
    }
@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-server/src/main/java/org/apache/tinkerpop/gremlin/server/util/TraverserIterator.java