@Override
  public void addCacheListener(CacheListener listener) {
    for (PartitionedRegion prQ : userRegionNameToShadowPRMap.values()) {
      AttributesMutator mutator = prQ.getAttributesMutator();
      mutator.addCacheListener(listener);
    }
  }
Take will choose a random BucketRegionQueue which is primary and will take the head element
from it.
geode-core/src/main/java/org/apache/geode/internal/cache/wan/parallel/ParallelGatewaySenderQueue.java