private Set<Integer> getAllWaitingBuckets(
        Map<PersistentMemberID, Set<Integer>> offlineMembers) {
      Set<Integer> allWaitingBuckets = new TreeSet<>();
      for (Set<Integer> missingPerMember : offlineMembers.values()) {
        allWaitingBuckets.addAll(missingPerMember);
      }
      return allWaitingBuckets;
    }
Get a consolodated set of all buckets that are waiting.
geode-core/src/main/java/org/apache/geode/internal/cache/partitioned/PersistentBucketRecoverer.java