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I'm trying to insert a simple row to a table in Cassandra 2.0.5, Storm version 0.9.0.1.

My test is as follows:

I have a table consisting of an id (int) and sentence (text) colum. id is the primary key.

My spout generates sentences and I add an ID (static increment in the code).

This is my topology:

TridentTopology topology = new TridentTopology();
StateFactory cassandraStateFactory = CassandraMapState.nonTransactional(options);
Fields fields = new Fields("id", "sentence");
MyTridentTupleMapper tupleMapper = new MyTridentTupleMapper(keyspace, fields);
CassandraUpdater updater = new CassandraUpdater(tupleMapper);
TridentState wordCounts = topology.newStream("spout1", spout)
            .each(new Fields("sentence"), new AddId(), new Fields("id"))
            .partitionPersist(cassandraStateFactory, fields, updater);

LocalCluster cluster = new LocalCluster();
cluster.submitTopology("test", config, topology.build());

The code for MyTridentTupleMapper:

https://github.com/guywald/trident-cassandra-read-write-examples/blob/master/src/test/java/com/guywald/storm/trident/cassandra/MyTridentTupleMapper.java

I get the following exception:

2014-02-08 22:20:14 ERROR executor:0 - 
java.lang.RuntimeException: java.lang.ClassCastException: storm.trident.state.map.SnapshottableMap cannot be cast to com.hmsonline.storm.cassandra.trident.CassandraState
    at backtype.storm.utils.DisruptorQueue.consumeBatchToCursor(DisruptorQueue.java:90)
    at backtype.storm.utils.DisruptorQueue.consumeBatchWhenAvailable(DisruptorQueue.java:61)
    at backtype.storm.disruptor$consume_batch_when_available.invoke(disruptor.clj:62)
    at backtype.storm.daemon.executor$fn__3498$fn__3510$fn__3557.invoke(executor.clj:730)
    at backtype.storm.util$async_loop$fn__444.invoke(util.clj:403)
    at clojure.lang.AFn.run(AFn.java:24)
    at java.lang.Thread.run(Thread.java:744)

I'm not sure why it returns this and would appreciate help.

Matthias J. Sax
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Guy Wald
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1 Answers1

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It looks like CassandraUpdater expects CassandraState, while CassandraMapState.nonTransactional creates SnapshottableMap which is not compatible. I believe common (or exotic custom) MapState updaters are to be used with CassandraMapState. There's a good explanation about when to use State vs MapState in here: https://groups.google.com/forum/#!topic/storm-user/TASr2zWyzKs

I think one should use CassandraStateFactory as a state factory for your example to work.

aljipa
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