blueflood-core/src/main/java/com/rackspacecloud/blueflood/io/datastax/DPreaggregatedMetricsRW.java
@VisibleForTesting
    @Override
    public void insertMetrics(Collection<IMetric> metrics,
                              Granularity granularity) throws IOException {

        Timer.Context ctx = Instrumentation.getWriteTimerContext(
                CassandraModel.getPreaggregatedColumnFamilyName(granularity));
        try {
            Multimap<Locator, IMetric> map = asMultimap(metrics);

            if ( isBatchIngestEnabled ) {
                insertMetricsInBatch(map, granularity);
            } else {
                insertMetricsIndividually(map, granularity);
            }
        } finally {
            ctx.stop();
        }
    }
@VisibleForTesting
    @Override
    public void insertMetrics(Collection<IMetric> metrics,
                              Granularity granularity) throws IOException {

        Timer.Context ctx = Instrumentation.getWriteTimerContext(
                CassandraModel.getPreaggregatedColumnFamilyName(granularity));
        try {
            Multimap<Locator, IMetric> map = asMultimap(metrics);

            if ( isBatchIngestEnabled ) {
                insertMetricsInBatch(map, granularity);
            } else {
                insertMetricsIndividually(map, granularity);
            }
        } finally {
            ctx.stop();
        }
    }
Inserts a collection of rolled up metrics to the metrics_preaggregated_{granularity} column family.
Only our tests should call this method. Services should call either insertMetrics(Collection metrics)
or insertRollups()

@param metrics
@throws IOException