@PipelineProperty(
            description = "The stroom-stats data source to record statistics against.",
            displayPriority = 1)
    @PipelinePropertyDocRef(types = StroomStatsStoreDoc.TYPE)
    public void setStatisticsDataSource(final DocRef stroomStatStoreRef) {
        this.stroomStatStoreRef = stroomStatStoreRef;
    }
A Kafka appender specifically for sending statistic event messages to kafka.
The key and topic are derived from the selected statistic data source
stroom-statistics/stroom-statistics-impl-hbase/src/main/java/stroom/statistics/impl/hbase/pipeline/StroomStatsAppender.java