variables across tasks in Storm bolt

Question

Field grouping can direct tuples with certain fields to the same task. One executor can contain several tasks.

If I declare a bolt with a private variable integer to count tuples.

public static class CountBolt implements IRichBolt {
    OutputCollector _collector;
    private int count;

    public void prepare(Map conf, TopologyContext context, OutputCollector collector) {
        _collector = collector;
        count = 0;
    }

    public void execute(Tuple tuple) {
        count = count + 1;
        _collector.ack(tuple);
    }

    public void cleanup() {
    }

    public void declareOutputFields(OutputFieldsDeclarer declarer) {
    }

    public Map getComponentConfiguration() {
        return null;
    }
}

Does this count show the total count of inputs of the same task or of the same executor?

Answer 1

The count will be per task. Each task has its own instance of your Spout/Bolt class.

It would be per worker, if the variable is declared static . (Not per executor because a worker might run multiple executors of the same Spout/Bolt.)