Storm Trident示例partitionBy

Posted 2020-10-28 nickt

如下代码使用partitionBy做repartition, partitionBy即根据相应字段的值按一定算法，把tuple分配到目标partition当中（Target Partition = hash(fields) % (number of target partition)），

相同值会被分配到同一个partition当中，由于不同值有可能出现相同的hash, 根据上面的算法，不同的值，也可能分配到同一个partition中。

省略部分代码，省略部分可参考：https://blog.csdn.net/nickta/article/details/79666918

 

FixedBatchSpout spout = new FixedBatchSpout(new Fields("user", "score"), 3,   
                new Values("nickt1", 4),  
                new Values("nickt2", 7),   
                new Values("nickt1", 8),  
                new Values("nickt4", 9),   
                new Values("nickt5", 7),  
                new Values("nickt1", 11),  
                new Values("nickt4", 5)  
                );  
        spout.setCycle(false);  
        TridentTopology topology = new TridentTopology();  
        topology.newStream("spout1", spout)  
                .partitionBy(new Fields("user"))  
                .each(new Fields("user"),new Debug("print:"))  
                .parallelismHint(5);  

　　

输出结果：由输出，可以看出，nickt1都是在partition1中输出，nickt4都是在partition4中输出

<Fri Mar 23 15:21:46 CST 2018[partition2-Thread-53-b-0-executor[35 35]]> DEBUG(print:): [nickt2]
<Fri Mar 23 15:21:46 CST 2018[partition1-Thread-128-b-0-executor[34 34]]> DEBUG(print:): [nickt1]
<Fri Mar 23 15:21:46 CST 2018[partition1-Thread-128-b-0-executor[34 34]]> DEBUG(print:): [nickt1]
<Fri Mar 23 15:21:46 CST 2018[partition1-Thread-128-b-0-executor[34 34]]> DEBUG(print:): [nickt1]
<Fri Mar 23 15:21:46 CST 2018[partition4-Thread-126-b-0-executor[37 37]]> DEBUG(print:): [nickt4]
<Fri Mar 23 15:21:46 CST 2018[partition0-Thread-72-b-0-executor[33 33]]> DEBUG(print:): [nickt5]
<Fri Mar 23 15:21:46 CST 2018[partition4-Thread-126-b-0-executor[37 37]]> DEBUG(print:): [nickt4]