This library provides core storm bolt on top of Apache Cassandra. Provides simple DSL to map storm Tuple to Cassandra Query Language Statement.

Configuration

CassandraWriterBolt

Property name	Description	Default
cassandra.keyspace	-
cassandra.nodes	-	{“localhost”}
cassandra.username	-	-
cassandra.password	-	-
cassandra.port	-	9092
cassandra.output.consistencyLevel	-	ONE
cassandra.batch.size.rows	-	100
cassandra.retryPolicy	-	DefaultRetryPolicy
cassandra.reconnectionPolicy.baseDelayMs	-	100 (ms)
cassandra.reconnectionPolicy.maxDelayMs	-	60000 (ms)

import static org.apache.storm.cassandra.DynamicStatementBuilder.*

Insert Query Builder

Insert query including only the specified tuple fields.


    new CassandraWriterBolt(
        async(
            simpleQuery("INSERT INTO album (title,year,performer,genre,tracks) VALUES (?, ?, ?, ?, ?);")
                .with(
                    fields("title", "year", "performer", "genre", "tracks")
                 )
            )
    );

Insert query including all tuple fields.


    new CassandraWriterBolt(
        async(
            simpleQuery("INSERT INTO album (title,year,performer,genre,tracks) VALUES (?, ?, ?, ?, ?);")
                .with( all() )
            )
    );

Insert multiple queries from one input tuple.

    new CassandraWriterBolt(
        async(
            simpleQuery("INSERT INTO titles_per_album (title,year,performer,genre,tracks) VALUES (?, ?, ?, ?, ?);").with(all())),
            simpleQuery("INSERT INTO titles_per_performer (title,year,performer,genre,tracks) VALUES (?, ?, ?, ?, ?);").with(all()))
        )
    );

Insert query using QueryBuilder

    new CassandraWriterBolt(
        async(
            simpleQuery("INSERT INTO album (title,year,perfomer,genre,tracks) VALUES (?, ?, ?, ?, ?);")
                .with(all()))
            )
    )

Insert query with static bound query

    new CassandraWriterBolt(
         async(
            boundQuery("INSERT INTO album (title,year,performer,genre,tracks) VALUES (?, ?, ?, ?, ?);")
                .bind(all());
         )
    );

Insert query with static bound query using named setters and aliases

    new CassandraWriterBolt(
         async(
            boundQuery("INSERT INTO album (title,year,performer,genre,tracks) VALUES (:ti, :ye, :pe, :ge, :tr);")
                .bind(
                    field("ti"),as("title"),
                    field("ye").as("year")),
                    field("pe").as("performer")),
                    field("ge").as("genre")),
                    field("tr").as("tracks"))
                ).byNamedSetters()
         )
    );

Insert query with bound statement load from storm configuration

    new CassandraWriterBolt(
         boundQuery(named("insertIntoAlbum"))
            .bind(all());

Insert query with bound statement load from tuple field

    new CassandraWriterBolt(
         boundQuery(namedByField("cql"))
            .bind(all());

Insert query with batch statement

    // Logged
    new CassandraWriterBolt(loggedBatch(
            simpleQuery("INSERT INTO titles_per_album (title,year,performer,genre,tracks) VALUES (?, ?, ?, ?, ?);").with(all())),
            simpleQuery("INSERT INTO titles_per_performer (title,year,performer,genre,tracks) VALUES (?, ?, ?, ?, ?);").with(all()))
        )
    );
// UnLogged
    new CassandraWriterBolt(unLoggedBatch(
            simpleQuery("INSERT INTO titles_per_album (title,year,performer,genre,tracks) VALUES (?, ?, ?, ?, ?);").with(all())),
            simpleQuery("INSERT INTO titles_per_performer (title,year,performer,genre,tracks) VALUES (?, ?, ?, ?, ?);").with(all()))
        )
    );

How to handle query execution results

The interface ExecutionResultHandler can be used to custom how an execution result should be handle.

public interface ExecutionResultHandler extends Serializable {
    void onQueryValidationException(QueryValidationException e, OutputCollector collector, Tuple tuple);

    void onReadTimeoutException(ReadTimeoutException e, OutputCollector collector, Tuple tuple);

    void onWriteTimeoutException(WriteTimeoutException e, OutputCollector collector, Tuple tuple);

    void onUnavailableException(UnavailableException e, OutputCollector collector, Tuple tuple);

    void onQuerySuccess(OutputCollector collector, Tuple tuple);
}

By default, the CassandraBolt fails a tuple on all Cassandra Exception (see BaseExecutionResultHandler) .

    new CassandraWriterBolt(insertInto("album").values(with(all()).build())
            .withResultHandler(new MyCustomResultHandler());

Declare Output fields

A CassandraBolt can declare output fields / stream output fields. For instance, this may be used to remit a new tuple on error, or to chain queries.

    new CassandraWriterBolt(insertInto("album").values(withFields(all()).build())
            .withResultHandler(new EmitOnDriverExceptionResultHandler());
            .withStreamOutputFields("stream_error", new Fields("message");

    public static class EmitOnDriverExceptionResultHandler extends BaseExecutionResultHandler {
        @Override
        protected void onDriverException(DriverException e, OutputCollector collector, Tuple tuple) {
            LOG.error("An error occurred while executing cassandra statement", e);
            collector.emit("stream_error", new Values(e.getMessage()));
            collector.ack(tuple);
        }
    }

Murmur3FieldGrouping

Murmur3StreamGrouping can be used to optimise cassandra writes. The stream is partitioned among the bolt’s tasks based on the specified row partition keys.

CassandraWriterBolt bolt = new CassandraWriterBolt(
    insertInto("album")
        .values(
            with(fields("title", "year", "performer", "genre", "tracks")
            ).build());
builder.setBolt("BOLT_WRITER", bolt, 4)
        .customGrouping("spout", new Murmur3StreamGrouping("title"))

Trident API support

storm-cassandra support Trident state API for inserting data into Cassandra.

        CassandraState.Options options = new CassandraState.Options(new CassandraContext());
        CQLStatementTupleMapper insertTemperatureValues = boundQuery(
                "INSERT INTO weather.temperature(weather_station_id, weather_station_name, event_time, temperature) VALUES(?, ?, ?, ?)")
                .bind(with(field("weather_station_id"), field("name").as("weather_station_name"), field("event_time").now(), field("temperature")));
        options.withCQLStatementTupleMapper(insertTemperatureValues);
        CassandraStateFactory insertValuesStateFactory =  new CassandraStateFactory(options);
        TridentState selectState = topology.newStaticState(selectWeatherStationStateFactory);
        stream = stream.stateQuery(selectState, new Fields("weather_station_id"), new CassandraQuery(), new Fields("name"));
        stream = stream.each(new Fields("name"), new PrintFunction(), new Fields("name_x"));
        stream.partitionPersist(insertValuesStateFactory, new Fields("weather_station_id", "name", "event_time", "temperature"), new CassandraStateUpdater(), new Fields());

        CassandraState.Options options = new CassandraState.Options(new CassandraContext());
        CQLStatementTupleMapper insertTemperatureValues = boundQuery("SELECT name FROM weather.station WHERE id = ?")
                 .bind(with(field("weather_station_id").as("id")));
        options.withCQLStatementTupleMapper(insertTemperatureValues);
        options.withCQLResultSetValuesMapper(new TridentResultSetValuesMapper(new Fields("name")));
        CassandraStateFactory selectWeatherStationStateFactory =  new CassandraStateFactory(options);
        CassandraStateFactory selectWeatherStationStateFactory = getSelectWeatherStationStateFactory();
        TridentState selectState = topology.newStaticState(selectWeatherStationStateFactory);
        stream = stream.stateQuery(selectState, new Fields("weather_station_id"), new CassandraQuery(), new Fields("name"));

Bolt API implementation for Apache Cassandra