我想实现一个连接语义,并尝试trident拓扑中的连接方法。我发现join是在批之间进行的。如果两个流之间的连接有数百万个元组,它是否必须在一个批内完成?
在genderspout中,每批有3个元组,因此喷口将发射2个批次agespout,每批有5个元组,因此喷口将仅发射1个批次
我用jointype做一个左外连接
测试代码的输出为:
1 man 15
2 woman 18
1 man 19
3 woman NULL
4 man NULL
1 woman NULL
从输出中,我发现前四个结果在genderspout的第一批和agespout的第一批之间连接。最后两个结果是genderspout的第二批和agespout的空批之间的连接。因此,对于连接语义,结果是不正确的,因为genderspoutleft join agespout的预期结果是:
1 man 15
1 man 19
2 woman 18
3 woman NULL
4 man 20
1 woman 15
1 woman 19
所以我的问题是:如果join的两边(喷口)有数百万个元组,我应该把它们放在一个批中才能得到正确的结果吗?
或者我的方法是错误的,你能告诉我怎样才能得到正确的外部连接语义的结果吗?
测试代码如下:
public static void main(String[] args) throws Exception{
Fields genderField = new Field("id", "gender");
FixedBatchSpout genderSpout = new FixedBatchSpout(genderField, 3,
new Values("1", "man"),
new Values("2", "woman"),
new Values("3", "woman"),
new Values("4", "man"),
new Values("1", "woman"));
genderSpout.setCycle(false);
Fields ageField = new Field("id2", "age");
FiexedBatchSpout ageSpout = new FixedBatchSpout(new Fields("id2", "age"), 5,
new Values("1", "15"),
new Values("4", "20"),
new Values("2", "18"),
new Values("1", "19"));
ageSpout.setCycle(false);
List<Stream> allStreams = new ArrayList<Stream>();
List<Fields> allFields = new ArrayList<Fields>();
List<Fields> joinFileds = new ArrayList<Fields>();
List<JoinType> joinTypes = new ArrayList<JoinType>();
TridentTopology topology = new TridentTopology();
Stream genderStream = topology.newStream("genderIn", genderSpout);
Stream ageStream = topology.newStream("ageIn", ageSpout);
allStreams.add(genderStream);
allStreams.add(ageStream);
allFields.add(genderFields);
allFields.add(ageFields);
joinFields.add(new Field("id")));
joinFields.add(new Field("id2"));
joinTypes.add(JoinType.INNER);
joinTypes.add(JoinType.OUTER);
topology.join(allStreams, joinFields, new Filds("id", "gender", "age"), joinTypes)
LocalCluster cluster = new LocalCluster();
Config config = new Config()
config.setDebug(false);
config.setMaxSpoutPending(3);
cluster.submitTopology("trident-join-test", config, topology.build());
Thread.sleep(3000);
cluster.shutdown();
}
1条答案
按热度按时间afdcj2ne1#
我以前也问过同样的问题https://groups.google.com/forum/?fromgroups=#!论坛/风暴用户:https://groups.google.com/forum/?fromgroups=#!主题/风暴用户/7fxavgf2\u
jason jackson的答案是:tridenttopology.join不会跨批进行连接。您可以使用statequery和partitionpersist之一跨批执行流连接。
希望有用