The dropwizard-cassandra library provides useful functionality for Dropwizard apps that communicate with Cassandra clusters. Under the hood, it uses the DataStax Cassandra Driver.

By default, the bundle includes:

• Configuration
• Managed Cluster
• Health Check
• Metrics
• Support for multiple clusters

A configuration class is defined for you with sensible defaults (wherever possible, relying on those provided by the driver). All you need to do is override the default configuration as required and then let the CassandraFactory do the work of wiring everything up correctly.

The Cluster instance is wrapped as a Managed object in Dropwizard, allowing it to be properly closed when the application terminates. Graceful termination is attempted first (with a configurable wait period), after which the cluster will be forcefully terminated. Remember that we're talking about the client driver being closed... not the actual Cassandra cluster.

A health check is registered automatically for you, ensuring that your application reports the correct status based on its ability to connect to Cassandra. The cluster is considered healthy if it can successfully execute the validationQuery defined in configuration.

DataStax already expose metrics directly from the Cluster instance, but CassandraFactory extracts and registers them with the MetricRegistry of your app - ensuring that they get correctly reported.

For apps that connect to multiple Cassandra clusters, all features described above are fully supported through separation by named clusters. Health checks and metrics are named according to cluster, allowing multiple separate clusters to operate safely within the same application.

Using the bundle is as simple as registering it in your Dropwizard application. The dependency can be found in Maven Central with the following coordinates:

<dependency>
  <groupId>org.stuartgunter</groupId>
  <artifactId>dropwizard-cassandra</artifactId>
  <version>${dropwizard-cassandra.version}</version>
</dependency>

Once you have the dependency registered, it's just a matter of adding CassandraFactory instances to your Configuration class:

public class YourAppConfig extends Configuration {

    @Valid
    @NotNull
    private CassandraFactory cassandra = new CassandraFactory();

    @JsonProperty("cassandra")
    public CassandraFactory getCassandraFactory() {
        return cassandra;
    }

    @JsonProperty("cassandra")
    public void setCassandraFactory(CassandraFactory cassandra) {
        this.cassandra = cassandra;
    }
}

Then, in your Application, build Cluster instances when you need them:

public class YourApp extends Application<YourAppConfig> {
    
    @Override
    public void run(YourAppConfig configuration, Environment environment) throws Exception {
        Cluster cassandra = configuration.getCassandraFactory().build(environment);
    }
}

The dropwizard-cassandra library defines a number of configuration options that are largely based on the requirements of the DataStax Cassandra driver. Some additional configuration is included for the bundle to register everything correctly with Dropwizard.

The full set of configuration options are shown below. Only configuration keys are shown; please see the JavaDocs on the various configuration classes for more details about the configuration options available and their default values - particularly for polymorphic configuration - e.g. ReconnectionPolicyFactory. There are also a number of smoke tests ensuring that the major configuration options are parseable. To find examples of particular config variants, take a look at the test resources folder.

clusterName:
keyspace:
validationQuery:
contactPoints:
port:
protocolVersion:
compression:
reconnectionPolicy:
  type:
authProvider:
  type:
retryPolicy:
  type:
loadBalancingPolicy:
  type:
speculativeExecutionPolicy:
  type:
queryOptions:
  consistencyLevel:
  serialConsistencyLevel:
  fetchSize:
socketOptions:
  connectTimeoutMillis:
  readTimeoutMillis:
  keepAlive:
  reuseAddress:
  soLinger:
  tcpNoDelay:
  receiveBufferSize:
  sendBufferSize:
poolingOptions:
  heartbeatInterval:
  poolTimeout:
  local:
    minSimultaneousRequests:
    maxSimultaneousRequests:
    coreConnections:
    maxConnections:
  remote:
    minSimultaneousRequests:
    maxSimultaneousRequests:
    coreConnections:
    maxConnections:
metricsEnabled:
jmxEnabled:
shutdownGracePeriod: