public int getMaxMappers()

in emr-dynamodb-hadoop/src/main/java/org/apache/hadoop/dynamodb/util/RoundRobinYarnContainerAllocator.java [26:64]

• 30 lines of code
• 7 McCabe index (conditional complexity)

  public int getMaxMappers(int nodes, int reducers, int nodeSlots, int appMasterSlots, int
      mapSlots, int reduceSlots) {
    // Initialize all nodes with fully available slots
    int[] clusterNodeSlots = new int[nodes];
    for (int k = 0; k < nodes; k++) {
      clusterNodeSlots[k] = nodeSlots;
    }

    // Allocate the app master in the 1st node
    clusterNodeSlots[0] -= appMasterSlots;

    // Find slots for all reducers using round robin
    int reducerIndex = 0;
    int nodeIndex = 1;
    for (; reducerIndex < reducers; reducerIndex++) {
      if (nodeIndex >= nodes) {
        nodeIndex = 0;
      }
      if (clusterNodeSlots[nodeIndex] >= reduceSlots) {
        clusterNodeSlots[nodeIndex] -= reduceSlots;
      } else {
        break;
      }
      nodeIndex++;
    }

    if (reducerIndex < reducers) {
      log.warn("All slots are used for the app master and reducers. No slots for mappers.");
      return 0;
    }

    // Use all remaining slots for mappers
    int mappers = 0;
    for (nodeIndex = 0; nodeIndex < nodes; nodeIndex++) {
      mappers += clusterNodeSlots[nodeIndex] / mapSlots;
    }

    return mappers;
  }