Henicea

Henicea was the sister of Cassandra in the Greek Mythology.

Migration

Henicea provides a simple migration mechanism for Java projects.

Example config class for Spring Boot:

CassandraConfig.java

@Configuration
@Slf4j
public class CassandraConfig {

    @Autowired
    private ResourcePatternResolver resourceResolver;

    @Autowired
    private Environment environment;

    @Bean
    public Migrator migrator() {
        return new Migrator();
    }

    @Bean
    public Cluster cluster() throws IOException {
        Cluster cluster = Cluster.builder()
                .addContactPoints(environment.getProperty("cassandra.contactPoints").split(","))
                .withPort(environment.getProperty("cassandra.port", Integer.class))
                .build();

        log.info("Running migrations");
        migrator().execute(cluster, environment.getProperty("cassandra.keyspace"), getMigrations());

        return cluster;
    }

    @Bean
    public Session session() throws Exception {
        return cluster().connect(environment.getProperty("cassandra.keyspace"));
    }

    private Resource[] getMigrations() throws IOException {
        return resourceResolver.getResources("classpath:/cassandra/*.cql");
    }
}

application.properties

cassandra.contactPoints=cassandra-node1,cassandra-node2
cassandra.port=9042
cassandra.keyspace=myapp

Migration files

The migration file can be named in any pattern. By default the files are sorted by name but the resourceComparator in the Migrator class has a setter to allow custom strategies.

Due to limitations in the driver, each migration file can have only one statement.

Waiting for Cassandra to start

This is a common situation when you use Docker for local development and functional tests, the Cassandra database will start in a separate container and it may take longer to get ready than your application. This library comes with a simple utility to help with retry and exponential back-off.

Cluster cluster = new Retryer()
        .onError((attempt, exception) -> log.warn("Could not connect to cassandra cluster on attempt number {}. Wrapped exception", attempt, exception))
        .withWait(TimeUnit.SECONDS, 1, 2, 4, 8, 10, 10)
        .run(() -> {
            Cluster candidate = Cluster.builder()
                    .addContactPoints("localhost")
                    .withPort(9042)
                    .build();

            candidate.init(); // will throw exception if none of the contact points can be reached

            return candidate;
        });

The run method will throw the last thrown exception if all the attempts failed.

Health check

Henicea provides a simple health check through Spring Boot Actuator. The only requirement is to have a Cassandra Session object in the Spring context.

To auto configure a health check add

@Bean
public CassandraHealthIndicator cassandraHealthIndicator() {
    return new CassandraHealthIndicator();
}

to your Java config class.