public Set<String> filterOutNonParallelGatewaySenders(Set<String> senderIds) {
    Set<String> allParallelSenders = cache.getAllGatewaySenders()
        .parallelStream()
        .filter(GatewaySender::isParallel)
        .map(GatewaySender::getId)
        .collect(toSet());

    Set<String> parallelSenders = new HashSet<>(senderIds);
    parallelSenders.retainAll(allParallelSenders);

    return parallelSenders;
  }
Filters out non parallel GatewaySenders.

@param senderIds set of gateway sender IDs.
@return set of parallel gateway senders present in the input set.
geode-core/src/main/java/org/apache/geode/internal/cache/PartitionedRegion.java