Storm确保消息被消费

以WordCount为例

源头 Spout

public class WordCountSpout implements IRichSpout {
    private TopologyContext context;
    private SpoutOutputCollector collector;

    private List<String> states;

    private Random r = new Random();

    private int index = 0;

    //消息集合, 存放所有消息
    private Map<Long, String> messages = new HashMap<Long, String>();

    //失败消息
    private Map<Long, Integer> failMessages = new HashMap<Long, Integer>();

    public void open(Map conf, TopologyContext context, SpoutOutputCollector collector) {
        this.context = context;
        this.collector = collector;
        states = new ArrayList<String>();
        states.add("hello world tom");
        states.add("hello world tomas");
        states.add("hello world tomasLee");
        states.add("hello world tomson");
    }

    public void close() {

    }

    public void activate() {

    }

    public void deactivate() {

    }

    public void nextTuple() {
        if (index < 3) {
            String line = states.get(r.nextInt(4));
            //取出时间戳
            long ts = System.currentTimeMillis();
            messages.put(ts, line);

            //发送元组，使用ts作为消息id
            collector.emit(new Values(line), ts);
            System.out.println(this + "nextTuple() : " + line + " : " + ts);
            index++;
        }
    }

    /**
     * 回调处理
     */
    public void ack(Object msgId) {
        //成功处理，删除失败重试.
        Long ts = (Long) msgId;
        failMessages.remove(ts);
        messages.remove(ts);
    }

    public void fail(Object msgId) {
        //时间戳作为msgId
        Long ts = (Long) msgId;
        //判断消息是否重试了3次
        Integer retryCount = failMessages.get(ts);
        retryCount = (retryCount == null ? 0 : retryCount);

        //超过最大重试次数
        if (retryCount >= 3) {
            failMessages.remove(ts);
            messages.remove(ts);
        } else {
            //重试
            collector.emit(new Values(messages.get(ts)), ts);
            System.out.println(this + "fail() : " + messages.get(ts) + " : " + ts);
            retryCount++;
            failMessages.put(ts, retryCount);
        }
    }

    public void declareOutputFields(OutputFieldsDeclarer declarer) {
        declarer.declare(new Fields("line"));
    }

    public Map<String, Object> getComponentConfiguration() {
        return null;
    }
}

分片 Bolt

public class SplitBolt implements IRichBolt {

    private TopologyContext context;
    private OutputCollector collector;

    public void prepare(Map stormConf, TopologyContext context, OutputCollector collector) {
        this.context = context;
        this.collector = collector;
    }

    public void execute(Tuple tuple) {
        String line = tuple.getString(0);
        if (new Random().nextBoolean()) {
            //确认
            collector.ack(tuple);
            System.out.println(this + " : ack() : " + line + " : " + tuple.getMessageId().toString());
        } else {
            //失败
            collector.fail(tuple);
            System.out.println(this + " : fail() : " + line + " : " + tuple.getMessageId().toString());
        }
    }

    public void cleanup() {

    }

    public void declareOutputFields(OutputFieldsDeclarer declarer) {
        declarer.declare(new Fields("word", "count"));

    }

    public Map<String, Object> getComponentConfiguration() {
        return null;
    }
}

WCApp

public class WCApp {
    public static void main(String[] args) throws Exception {
        TopologyBuilder builder = new TopologyBuilder();
        //设置Spout
        builder.setSpout("wcspout", new WordCountSpout()).setNumTasks(1);
        //设置creator-Bolt
        builder.setBolt("split-bolt", new SplitBolt(), 2).shuffleGrouping("wcspout").setNumTasks(2);

        Config conf = new Config();
        conf.setNumWorkers(2);
        conf.setDebug(true);

        /**
         * 本地模式storm
         */
        LocalCluster cluster = new LocalCluster();
        cluster.submitTopology("wc", conf, builder.createTopology());
        System.out.println("hello world llll");
    }
}