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https://github.com/instaclustr/cassandra-sstable-generator

Tool for programmatic generation of Cassandra SSTable
https://github.com/instaclustr/cassandra-sstable-generator

bulk cassandra csv generation load netapp-public random sstable

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Tool for programmatic generation of Cassandra SSTable

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# Cassandra-SStable-Generator



_CLI tool for programmatic generation of Cassandra SSTables_



image:https://img.shields.io/maven-central/v/com.instaclustr/sstable-generator.svg?label=Maven%20Central[link=https://search.maven.org/search?q=g:%22com.instaclustr%22%20AND%20a:%22sstable-generator%22]

image:https://circleci.com/gh/instaclustr/cassandra-sstable-generator.svg?style=svg["Instaclustr",link="https://circleci.com/gh/instaclustr/cassandra-sstable-generator"]



- Website: https://www.instaclustr.com/

- Documentation: https://www.instaclustr.com/support/documentation/



This tool simply generates SSTables programmatically. It uses Cassandra's `CQLSSTableWriter`.

After the generation of SSTables is finished, you can load them by `sstableloader` tool as usual.



The project consists of these modules:



* api—impl is coded against this module

* impl—the implementation of your population logic, depends on `api`

* generator—the implementation of whole generator CLI application

* cassandra-3—the implementation of SSTable generator using internals of Cassandra 3 artifact

* cassandra- 4—the implementation of SSTable generator using internals of Cassandra 4 artifact



## Build



`mvn clean install` (or `mvn clean install -DskipTests`)



## Run



Let's guide you through an example. We want to generate a SSTable by Cassandra 3 API so we can load it

to Cassandra afterwards. The components you need to have on a class path are as follows:



* generator jar

* cassandra-3 module jar

* jar with the implementation of your generation logic



----

java \

  -cp /path/to/impl-1.0.jar:/path/to/generator-1.0.jar:/path/to/cassandra-3.jar \

  com.instaclustr.sstable.generator.LoaderApplication \

  _command_ \

  _arguments_

----



The concrete example of the invocation would be:



----

java \

    -cp impl/target/sstable-generator-impl-1.0:generator/target/sstable-generator-1.0.jar:cassandra-3/target/cassandra-3-1.0.jar \

    com.instaclustr.sstable.generator.LoaderApplication \

    fixed \

    --keyspace mykeyspace \

    --table mytable \

    --output-dir=/tmp/output \

    --schema cassandra-3/src/test/resources/cassandra/cql/table.cql \

    --threads 2

----



**Please be aware that you need to have all libraries of Apache Cassandra on the classpath as well. For

that reason, please use `./run.sh` script and modify it to suit your needs in order to generate SStables.**



No `command` executes default command—`help`:



----

Usage:  [-V] COMMAND

  -V, --version   print version information and exit

Commands:

  csv     tool for bulk-loading of data from csv

  random  tool for bulk-loading of random data

  fixed   tool for bulk-loading of fixed data

----



### `random` Command



By this command, you are expected to provide data which represents a row in random fashion.



### `csv` Command



`csv` command has same arguments as `random` but `--file` is mandatory. There is supposed to be CSV file which

represents rows. Each row will be parsed into a list of strings passed to `RowMapper` implementation where you

have to map them to list of objects for a Cassandra INSERT statement as values.



### `fixed` Command



By `fixed` command, we will generate a SSTable by using the exact list of "rows" with columns. This

will be obvious from the documentation which follows.



## Row Generation



In order to generate data for all three cases above you have to implement interface

`com.instaclustr.cassandra.bulkloader.RowMapper` in `api` module. This implementation should

be placed in `impl` (or its equivalent) and it should be on a class path.



## RowMapper Interface



----

public interface RowMapper {



    /**

     * Maps list of strings from whatever input representing

     * a row to list of objects to insert into Cassandra.

     *


     * This method e.g. called upon generation from CSV file.

     *


     * @param row where values are consisting of list of strings

     * @return list of objects to put to insert statement

     */

    List map(final List row);



    /**

     * Used when we do not want to generate data randomly but we have exact list of what to insert.

     *

     * @return list of rows to be created containing list of cells

     */

    Stream> get();



    /**

     * Logically same as {@link #map(List)} but all data per row

     * needs to be generated inside of the method. The number

     * of items in the returned list has to match number of columns

     * in a row. Each such object represents value which will be

     * passed to Cassandra INSERT statement.

     * 


     * This method is called repeatedly. Number of calls

     * is equal to paramter `--numberOfRecords`.

     *


     * This method is called upon "random" generation.

     * @return list of objects to put to insert statement

     */

    List random();



    /**

     * @return string representation of INSERT INTO statement. Question marks in VALUES are not

     * meant to be replaced.

     * 


     * For example: 'INSERT INTO keyspace.table (field1, field2, field3) VALUES (?, ?, ?)'

     */

    String insertStatement();

}

----



The implementation of `RowMapper` you are supposed to place on the class path would look like this:



----

public class RowMapper1 implements RowMapper {



    public static final String KEYSPACE = "mykeyspace";

    public static final String TABLE = "mytable";



    public static final UUID UUID_1 = UUID.randomUUID();

    public static final UUID UUID_2 = UUID.randomUUID();

    public static final UUID UUID_3 = UUID.randomUUID();



    @Override

    public List map(final List row) {

        return null;

    }



    @Override

    public Stream> get() {

        return Stream.of(

            new ArrayList() {{

                add(UUID_1);

                add("John");

                add("Doe");

            }},

            new ArrayList() {{

                add(UUID_2);

                add("Marry");

                add("Poppins");

            }},

            new ArrayList() {{

                add(UUID_3);

                add("Jim");

                add("Jack");

            }});

    }



    @Override

    public List random() {

        return null;

    }



    @Override

    public String insertStatement() {

        return format("INSERT INTO %s.%s (id, name, surname) VALUES (?, ?, ?);", KEYSPACE, TABLE);

    }

}

----



## SPI Mechanism



There is a Java SPI mechanism for implementation discovery, so it means that besides implementing API

you have to change the `impl/src/main/resources/META-INF/services/com.instaclustr.sstable.generator.RowMapper`

file containing FQCN of your implemenation on one line.



Once the `impl` jar is placed on the class path, it will be automatically discovered by the `generator` module so

you do not need to use any command-line arguments. Merely putting that JAR on the class path does the job.



The same mechanism works for `cassandra-3/4` jar. In case you want to generate jars by `CQLSSTableWriter`

for Cassandra 3, just put that jar on the class path. If you want to generate "Cassandra 4 SSTables", place the

respective `cassandra-4.jar` on the class path as shown above.



In practice this means that you need to compile only an `impl` module which contains one class so the compilation

and JAR building will take literally a few seconds (less than 1 sec here). The command line arguments for all will look

the same.



## Further Information

- See blog by Anup Shirolkar ["A Comprehensive Guide to Cassandra Architecture"](https://www.instaclustr.com/cassandra-architecture/)

- See blog by Anup Shirolkar ["Apache Cassandra Compaction Strategies

"](https://www.instaclustr.com/apache-cassandra-compaction/)

- Please see https://www.instaclustr.com/support/documentation/announcements/instaclustr-open-source-project-status/ for Instaclustr support status of this project