com.datastax.driver.core

Class Cluster

java.lang.Object

com.datastax.driver.core.Cluster

All Implemented Interfaces:

Closeable, AutoCloseable

public class Cluster
extends Object
implements Closeable

Information and known state of a Cassandra cluster.

This is the main entry point of the driver. A simple example of access to a Cassandra cluster would be:

   Cluster cluster = Cluster.builder().addContactPoint("192.168.0.1").build();
   Session session = cluster.connect("db1");

   for (Row row : session.execute("SELECT * FROM table1"))
       // do something ...
 

A cluster object maintains a permanent connection to one of the cluster nodes which it uses solely to maintain information on the state and current topology of the cluster. Using the connection, the driver will discover all the nodes currently in the cluster as well as new nodes joining the cluster subsequently.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Cluster.Builder Helper class to build Cluster instances.
static interface	Cluster.Initializer Initializer for Cluster instances.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Cluster(Cluster.Initializer initializer) Constructs a new Cluster instance.
protected	Cluster(String name, List<InetSocketAddress> contactPoints, Configuration configuration) Constructs a new Cluster instance.

Method Summary

Methods

Modifier and Type	Method and Description
static Cluster.Builder	builder() Creates a new Cluster.Builder instance.
static Cluster	buildFrom(Cluster.Initializer initializer) Build a new cluster based on the provided initializer.
void	close() Initiates a shutdown of this cluster instance and blocks until that shutdown completes.
CloseFuture	closeAsync() Initiates a shutdown of this cluster instance.
Session	connect() Creates a new session on this cluster and initialize it.
Session	connect(String keyspace) Creates a new session on this cluster, initialize it and sets the keyspace to the provided one.
String	getClusterName() The name of this cluster object.
Configuration	getConfiguration() The cluster configuration.
static String	getDriverVersion() Returns the current version of the driver.
Metadata	getMetadata() Returns read-only metadata on the connected cluster.
Metrics	getMetrics() The cluster metrics.
Cluster	init() Initialize this Cluster instance.
boolean	isClosed() Whether this Cluster instance has been closed.
Session	newSession() Creates a new session on this cluster but does not initialize it.
Cluster	register(Host.StateListener listener) Registers the provided listener to be notified on hosts up/down/added/removed events.
Cluster	register(LatencyTracker tracker) Registers the provided tracker to be updated with hosts read latencies.
Cluster	unregister(Host.StateListener listener) Unregisters the provided listener from being notified on hosts events.
Cluster	unregister(LatencyTracker tracker) Unregisters the provided latency tracking from being updated with host read latencies.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Cluster

protected Cluster(String name,
       List<InetSocketAddress> contactPoints,
       Configuration configuration)

Constructs a new Cluster instance.

This constructor is mainly exposed so Cluster can be sub-classed as a means to make testing/mocking easier or to "intercept" its method call. Most users shouldn't extend this class however and should prefer either using the builder() or calling buildFrom(com.datastax.driver.core.Cluster.Initializer) with a custom Initializer.

Parameters:

name - the name to use for the cluster (this is not the Cassandra cluster name, see getClusterName()).

contactPoints - the list of contact points to use for the new cluster.

configuration - the configuration for the new cluster.

Cluster

protected Cluster(Cluster.Initializer initializer)

Constructs a new Cluster instance.

This constructor is mainly exposed so Cluster can be sub-classed as a means to make testing/mocking easier or to "intercept" its method call. Most users shouldn't extend this class however and should prefer using the builder().

Parameters:

initializer - the initializer to use.

See Also:

buildFrom(com.datastax.driver.core.Cluster.Initializer)

Method Detail

init

public Cluster init()

Initialize this Cluster instance. This method creates an initial connection to one of the contact points used to construct the Cluster instance. That connection is then used to populate the cluster Metadata.

Calling this method is optional in the sense that any call to one of the connect methods of this object will automatically trigger a call to this method beforehand. It is thus only useful to call this method if for some reason you want to populate the metadata (or test that at least one contact point can be reached) without creating a first Session.

Please note that this method only creates one control connection for gathering cluster metadata. In particular, it doesn't create any connection pools. Those are created when a new Session is created through connect.

This method has no effect if the cluster is already initialized.

Returns:

this Cluster object.

Throws:

NoHostAvailableException - if no host amongst the contact points can be reached.

AuthenticationException - if an authentication error occurs while contacting the initial contact points.

IllegalStateException - if the Cluster was closed prior to calling this method. This can occur either directly (through close() or closeAsync()), or as a result of an error while initializing the Cluster.

buildFrom

public static Cluster buildFrom(Cluster.Initializer initializer)

Build a new cluster based on the provided initializer.

Note that for building a cluster pragmatically, Cluster.Builder provides a slightly less verbose shortcut with Cluster.Builder.build().

Also note that that all the contact points provided by initializer must share the same port.

Parameters:

initializer - the Cluster.Initializer to use

Returns:

the newly created Cluster instance

Throws:

IllegalArgumentException - if the list of contact points provided by initializer is empty or if not all those contact points have the same port.

builder

public static Cluster.Builder builder()

Creates a new Cluster.Builder instance.

This is a convenience method for new Cluster.Builder().

Returns:

the new cluster builder.

getDriverVersion

public static String getDriverVersion()

Returns the current version of the driver.

This is intended for products that wrap or extend the driver, as a way to check compatibility if end-users override the driver version in their application.

Returns:

the version.

newSession

public Session newSession()

Creates a new session on this cluster but does not initialize it.

Because this method does not perform any initialization, it cannot fail. The initialization of the session (the connection of the Session to the Cassandra nodes) will occur if either the Session.init() method is called explicitly, or whenever the returned session object is used.

Once a session returned by this method gets initialized (see above), it will be set to no keyspace. If you want to set such session to a keyspace, you will have to explicitly execute a 'USE mykeyspace' query.

Note that if you do not particularly need to defer initialization, it is simpler to use one of the connect() method of this class.

Returns:

a new, non-initialized session on this cluster.

connect

public Session connect()

Creates a new session on this cluster and initialize it.

Note that this method will initialize the newly created session, trying to connect to the Cassandra nodes before returning. If you only want to create a Session object without initializing it right away, see newSession().

Returns:

a new session on this cluster sets to no keyspace.

Throws:

NoHostAvailableException - if the Cluster has not been initialized yet (init() has not be called and this is the first connect call) and no host amongst the contact points can be reached.

AuthenticationException - if an authentication error occurs while contacting the initial contact points.

IllegalStateException - if the Cluster was closed prior to calling this method. This can occur either directly (through close() or closeAsync()), or as a result of an error while initializing the Cluster.

connect

public Session connect(String keyspace)

Creates a new session on this cluster, initialize it and sets the keyspace to the provided one.

Note that this method will initialize the newly created session, trying to connect to the Cassandra nodes before returning. If you only want to create a Session object without initializing it right away, see newSession().

Parameters:

keyspace - The name of the keyspace to use for the created Session.

Returns:

a new session on this cluster sets to keyspace keyspaceName.

Throws:

NoHostAvailableException - if the Cluster has not been initialized yet (init() has not be called and this is the first connect call) and no host amongst the contact points can be reached, or if no host can be contacted to set the keyspace.

AuthenticationException - if an authentication error occurs while contacting the initial contact points.

IllegalStateException - if the Cluster was closed prior to calling this method. This can occur either directly (through close() or closeAsync()), or as a result of an error while initializing the Cluster.

getClusterName

public String getClusterName()

The name of this cluster object.

Note that this is not the Cassandra cluster name, but rather a name assigned to this Cluster object. Currently, that name is only used for one purpose: to distinguish exposed JMX metrics when multiple Cluster instances live in the same JVM (which should be rare in the first place). That name can be set at Cluster building time (through Cluster.Builder.withClusterName(java.lang.String) for instance) but will default to a name like cluster1 where each Cluster instance in the same JVM will have a different number.

Returns:

the name for this cluster instance.

getMetadata

public Metadata getMetadata()

Returns read-only metadata on the connected cluster.

This includes the known nodes with their status as seen by the driver, as well as the schema definitions. Since this return metadata on the connected cluster, this method may trigger the creation of a connection if none has been established yet (neither init() nor connect() has been called yet).

Returns:

the cluster metadata.

Throws:

NoHostAvailableException - if the Cluster has not been initialized yet and no host amongst the contact points can be reached.

AuthenticationException - if an authentication error occurs while contacting the initial contact points.

IllegalStateException - if the Cluster was closed prior to calling this method. This can occur either directly (through close() or closeAsync()), or as a result of an error while initializing the Cluster.

getConfiguration

public Configuration getConfiguration()

The cluster configuration.

Returns:

the cluster configuration.

getMetrics

public Metrics getMetrics()

The cluster metrics.

Returns:

the cluster metrics, or null if metrics collection has been disabled (that is if Configuration.getMetricsOptions() returns null).

register

public Cluster register(Host.StateListener listener)

Registers the provided listener to be notified on hosts up/down/added/removed events.

Registering the same listener multiple times is a no-op.

Note that while LoadBalancingPolicy implements Host.StateListener, the configured load balancing does not need to (and should not) be registered through this method to received host related events.

Parameters:

listener - the new Host.StateListener to register.

Returns:

this Cluster object;

unregister

public Cluster unregister(Host.StateListener listener)

Unregisters the provided listener from being notified on hosts events.

This method is a no-op if listener hadn't previously be registered against this Cluster.

Parameters:

listener - the Host.StateListener to unregister.

Returns:

this Cluster object;

register

public Cluster register(LatencyTracker tracker)

Registers the provided tracker to be updated with hosts read latencies.

Registering the same listener multiple times is a no-op.

Be wary that the registered tracker update method will be call very frequently (at the end of every query to a Cassandra host) and should thus not be costly.

The main use case for a LatencyTracker is so LoadBalancingPolicy can implement latency awareness Typically, LatencyAwarePolicy registers it's own internal LatencyTracker (automatically, you don't have to call this method directly).

Parameters:

tracker - the new LatencyTracker to register.

Returns:

this Cluster object;

unregister

public Cluster unregister(LatencyTracker tracker)

Unregisters the provided latency tracking from being updated with host read latencies.

This method is a no-op if tracker hadn't previously be registered against this Cluster.

Parameters:

tracker - the LatencyTracker to unregister.

Returns:

this Cluster object;

closeAsync

public CloseFuture closeAsync()

Initiates a shutdown of this cluster instance.

This method is asynchronous and return a future on the completion of the shutdown process. As soon a the cluster is shutdown, no new request will be accepted, but already submitted queries are allowed to complete. This method closes all connections from all sessions and reclaims all resources used by this Cluster instance.

If for some reason you wish to expedite this process, the CloseFuture.force() can be called on the result future.

This method has no particular effect if the cluster was already closed (in which case the returned future will return immediately).

Returns:

a future on the completion of the shutdown process.

close

public void close()

Initiates a shutdown of this cluster instance and blocks until that shutdown completes.

This method is a shortcut for closeAsync().get().

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

isClosed

public boolean isClosed()

Whether this Cluster instance has been closed.

Note that this method returns true as soon as one of the close methods (closeAsync() or close()) has been called, it does not guarantee that the closing is done. If you want to guarantee that the closing is done, you can call close() and wait until it returns (or call the get method on closeAsync() with a very short timeout and check this doesn't timeout).

Returns:

true if this Cluster instance has been closed, false otherwise.