@Override
  public void logRollRequested(WALActionsListener.RollRequestReason reason) {
    source.incrementLogRollRequested();
    switch (reason) {
      case ERROR:
        source.incrementErrorLogRoll();
        break;
      case LOW_REPLICATION:
        source.incrementLowReplicationLogRoll();
        break;
      case SIZE:
        source.incrementSizeLogRoll();
        break;
      case SLOW_SYNC:
        source.incrementSlowSyncLogRoll();
        break;
      default:
        break;
    }
  }
Class used to push numbers about the WAL into the metrics subsystem. This will take a single
function call and turn it into multiple manipulations of the hadoop metrics system.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/MetricsWAL.java