private void addRemovedEventsToMap(Map<Integer, List<Object>> bucketIdToDispatchedKeys,
      int bucketId, List<Object> keys) {
    List<Object> dispatchedKeys = bucketIdToDispatchedKeys.get(bucketId);
    if (dispatchedKeys == null) {
      dispatchedKeys = keys == null ? new ArrayList<>() : keys;
    } else {
      dispatchedKeys.addAll(keys);
    }
    bucketIdToDispatchedKeys.put(bucketId, dispatchedKeys);
  }
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