JarCastingHenicea
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.
