static PartitionInfo getGroupInfo()

in modules/core/src/main/java/org/apache/fluo/core/worker/finder/hash/PartitionManager.java [110:152]

• 29 lines of code
• 5 McCabe index (conditional complexity)

  static PartitionInfo getGroupInfo(String me, SortedSet<String> children,
      Collection<TableRange> tablets, int groupSize) {

    int numGroups = Math.max(1, children.size() / groupSize);
    int[] groupSizes = new int[numGroups];
    int count = 0;
    int myGroupId = -1;
    int myId = -1;

    for (String child : children) {
      if (child.equals(me)) {
        myGroupId = count;
        myId = groupSizes[count];
      }
      groupSizes[count]++;
      count = (count + 1) % numGroups;
    }

    List<TableRange> rangesCopy = new ArrayList<>(tablets);
    Collections.sort(rangesCopy);

    // The behavior of Random with a given seed and shuffle are the same across different versions
    // of java. Both specify the algorithms in their javadoc and are meant to behave the same across
    // versions. This is important because different workers may be running different versions of
    // Java, but all workers need to do the same shuffle.
    //
    // Did try to use hashing to partition the tablets among groups, but it was slightly uneven. One
    // group having a 10% more tablets would lead to uneven utilization.
    Collections.shuffle(rangesCopy, new Random(42));

    List<TableRange> groupsTablets = new ArrayList<>();

    count = 0;
    for (TableRange tr : rangesCopy) {
      if (count == myGroupId) {
        groupsTablets.add(tr);
      }
      count = (count + 1) % numGroups;
    }

    return new PartitionInfo(myId, myGroupId, groupSizes[myGroupId], numGroups, children.size(),
        groupsTablets);
  }