com.aquenos.cassandra.pvarchiver.server.database

Class ThrottlingCassandraProvider

java.lang.Object

com.aquenos.cassandra.pvarchiver.server.database.ThrottlingCassandraProvider

All Implemented Interfaces:

CassandraProvider, Aware, InitializingBean, ApplicationEventPublisherAware

@ManagedResource(description="provides a throttling Cassandra session")
public class ThrottlingCassandraProvider
extends Object
implements ApplicationEventPublisherAware, CassandraProvider, InitializingBean

Cassandra provider that wraps another Cassandra Provider and supplies a ThrottlingSession.

This implementation of the CassandraProvider interface takes another Cassandra provider (that is set through the setCassandraProvider(CassandraProvider)) method and wraps the Session provided by this Cassandra provider in a ThrottlingSession. This implementation is useful when a component expects a Cassandra provider and not a session to be injected.

For convenience, this class is annotated with the ManagedResource annotation and thus exposes information about its configuration and the current status of the ThrottlingSession through JMX.

Please refer to the documentation of ThrottlingSession for limitations of the throttling logic.

Author:

Sebastian Marsching

Constructor Summary

Constructors

Constructor and Description
ThrottlingCassandraProvider()

Method Summary

Modifier and Type	Method and Description
void	afterPropertiesSet()
Cluster	getCluster() Returns a reference to the Cassandra cluster.
ListenableFuture<Cluster>	getClusterFuture() Returns a future reference to the Cassandra cluster.
int	getMaxConcurrentReadStatements() Returns the maximum number of read statements that are executed concurrently.
int	getMaxConcurrentWriteStatements() Returns the maximum number of write statements that are executed concurrently.
int	getPendingReadStatements() Returns the current number of read statements that are waiting for execution.
int	getPendingWriteStatements() Returns the current number of write statements that are waiting for execution.
int	getRunningReadStatements() Returns the current number of read statements that are running.
int	getRunningWriteStatements() Returns the current number of write statements that are running.
Session	getSession() Returns a reference to the Cassandra session.
ListenableFuture<Session>	getSessionFuture() Returns a future reference to the Cassandra session.
boolean	isInitialized() Tells whether this provider has been completely initialized.
void	onCassandraProviderInitializedEvent(CassandraProviderInitializedEvent event) Handles CassandraProviderInitializedEvents.
void	setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher)
void	setCassandraProvider(CassandraProvider cassandraProvider) Sets the backing Cassandra provider that provides access to the Apache Cassandra database.
void	setMaxConcurrentReadStatements(int maxConcurrentReadStatements) Set the maximum number of read statements that are executed concurrently.
void	setMaxConcurrentWriteStatements(int maxConcurrentWriteStatements) Set the maximum number of write statements that are executed concurrently.

Methods inherited from class java.lang.Object

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

Constructor Detail

ThrottlingCassandraProvider

public ThrottlingCassandraProvider()

Method Detail

afterPropertiesSet

public void afterPropertiesSet()
                        throws Exception

Specified by:

afterPropertiesSet in interface InitializingBean

Throws:

Exception

getCluster

public Cluster getCluster()

Description copied from interface: CassandraProvider

Returns a reference to the Cassandra cluster.

Specified by:

getCluster in interface CassandraProvider

Returns:

reference to the Cassandra cluster.

See Also:

CassandraProvider.getClusterFuture()

getClusterFuture

public ListenableFuture<Cluster> getClusterFuture()

Description copied from interface: CassandraProvider

Returns a future reference to the Cassandra cluster. The returned future completes when the cluster instance become available. The future might not complete for a very long time if a connection to the cluster cannot be established. The returned future will only throw an exception if the Cassandra provider is destroyed before the cluster instance becomes available. In all other cases, the Cassandra provider will wait for a later attempt to create a cluster instance to succeed.

Specified by:

getClusterFuture in interface CassandraProvider

Returns:

future that provides access to the Cassandra cluster instance once it becomes available. The cluster will be the same one as the one returned by CassandraProvider.getCluster().

See Also:

CassandraProvider.getCluster()

getMaxConcurrentReadStatements

@ManagedAttribute(description="maximum number of read statements that are executed concurrently")
public int getMaxConcurrentReadStatements()

Returns the maximum number of read statements that are executed concurrently. This is the value of the configuration parameter that is used when creating the ThrottlingSession. The default value is Integer.MAX_VALUE, effectively not limiting the number of concurrent statements. This property is exposed through JMX (read only).

Returns:

maximum number of read statements run concurrently.

See Also:

setMaxConcurrentReadStatements(int)

getMaxConcurrentWriteStatements

@ManagedAttribute(description="maximum number of write statements that are executed concurrently")
public int getMaxConcurrentWriteStatements()

Returns the maximum number of write statements that are executed concurrently. This is the value of the configuration parameter that is used when creating the ThrottlingSession. The default value is Integer.MAX_VALUE, effectively not limiting the number of concurrent statements. This property is exposed through JMX (read only).

Returns:

maximum number of write statements run concurrently.

See Also:

setMaxConcurrentWriteStatements(int)

getPendingReadStatements

@ManagedAttribute(description="number of read statements that are currently waiting for execution")
public int getPendingReadStatements()

Returns the current number of read statements that are waiting for execution. This method delegates to ThrottlingSession.getPendingReadStatementsCount(). If the session has not been initialized yet, this method returns zero. This property is exposed through JMX (read only).

Returns:

number of read statements that are currently waiting for execution.

getPendingWriteStatements

@ManagedAttribute(description="number of write statements that are currently waiting for execution")
public int getPendingWriteStatements()

Returns the current number of write statements that are waiting for execution. This method delegates to ThrottlingSession.getPendingWriteStatementsCount(). If the session has not been initialized yet, this method returns zero. This property is exposed through JMX (read only).

Returns:

number of write statements that are currently waiting for execution.

getRunningReadStatements

@ManagedAttribute(description="number of read statements that are currently being executed")
public int getRunningReadStatements()

Returns the current number of read statements that are running. A statement is running when the backing session's executeAsync method has been called but the future returned by that method has not completed yet. This method delegates to ThrottlingSession.getRunningReadStatementsCount(). If the session has not been initialized yet, this method returns zero. This property is exposed through JMX (read only).

Returns:

number of read statements that are currently being executed.

getRunningWriteStatements

@ManagedAttribute(description="number of write statements that are currently being executed")
public int getRunningWriteStatements()

Returns the current number of write statements that are running. A statement is running when the backing session's executeAsync method has been called but the future returned by that method has not completed yet. This method delegates to ThrottlingSession.getRunningReadStatementsCount(). If the session has not been initialized yet, this method returns zero. This property is exposed through JMX (read only).

Returns:

number of write statements that are currently being executed.

getSession

public Session getSession()

Description copied from interface: CassandraProvider

Returns a reference to the Cassandra session. The session can be used to run queries on the Cassandra cluster. The provider might bind the session to the correct keyspace so that other components can automatically operate on the keyspace without having to know the keyspace name.

Specified by:

getSession in interface CassandraProvider

Returns:

reference to the Cassandra session.

See Also:

CassandraProvider.getSessionFuture()

getSessionFuture

public ListenableFuture<Session> getSessionFuture()

Description copied from interface: CassandraProvider

Returns a future reference to the Cassandra session. The returned future completes when the session instance become available. The future might not complete for a very long time if a connection to the cluster cannot be established or the keyspace cannot be accessed. The returned future will only throw an exception if the Cassandra provider is destroyed before the session instance becomes available. In all other cases, the Cassandra provider will wait for a later attempt to create a session instance to succeed.

Specified by:

getSessionFuture in interface CassandraProvider

Returns:

future that provides access to the Cassandra session instance once it becomes available. The session will be the same one as the one returned by CassandraProvider.getSession().

See Also:

CassandraProvider.getSession()

isInitialized

public boolean isInitialized()

Description copied from interface: CassandraProvider

Tells whether this provider has been completely initialized. If true, CassandraProvider.getCluster() and CassandraProvider.getSession() will return a result and not throw an exception.

Please note that the provider might be destroyed after calling this method. In this case, CassandraProvider.getCluster() and CassandraProvider.getSession() might throw, even if this method returned true previously.

Specified by:

isInitialized in interface CassandraProvider

Returns:

true if this provider is ready for operation, false otherwise.

onCassandraProviderInitializedEvent

@EventListener
public void onCassandraProviderInitializedEvent(CassandraProviderInitializedEvent event)

Handles CassandraProviderInitializedEvents. If such an event is sent by the backing Cassandra provider (that has been set through setCassandraProvider(CassandraProvider)), it is resent, replacing the source with this provider. This ensures that components that use this Cassandra provider instead of the original one are notified correctly.

Parameters:

event - initialization event sent by the original CassandraProvider.

setApplicationEventPublisher

public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher)

Specified by:

setApplicationEventPublisher in interface ApplicationEventPublisherAware

setCassandraProvider

public void setCassandraProvider(CassandraProvider cassandraProvider)

Sets the backing Cassandra provider that provides access to the Apache Cassandra database. That Cassandra provider is used to back this Cassandra provider. Most methods of the CassandraProvider interface are simply forwarded to the original Cassandra provider. The getSession() and getSessionFuture() methods however do not forward directly, but return a ThrottlingSession instead.

Parameters:

cassandraProvider - original provider that provides a connection to the Apache Cassandra database.

Throws:

IllegalStateException - if this object has already been initialized ( afterPropertiesSet() has been called).

setMaxConcurrentReadStatements

public void setMaxConcurrentReadStatements(int maxConcurrentReadStatements)

Set the maximum number of read statements that are executed concurrently. When more statements are submitted to the session before the previously submitted statements have been executed, those statements are queued for later execution. This is the value of the configuration parameter that is used when creating the ThrottlingSession. The default value is Integer.MAX_VALUE, effectively not limiting the number of concurrent statements.

Parameters:

maxConcurrentReadStatements - maximum number of read statements that can run concurrently (must be greater than zero).

Throws:

IllegalArgumentException - if the specified value is less than one.

IllegalStateException - if this object has already been initialized ( afterPropertiesSet() has been called).

setMaxConcurrentWriteStatements

public void setMaxConcurrentWriteStatements(int maxConcurrentWriteStatements)

Set the maximum number of write statements that are executed concurrently. When more statements are submitted to the session before the previously submitted statements have been executed, those statements are queued for later execution. This is the value of the configuration parameter that is used when creating the ThrottlingSession. The default value is Integer.MAX_VALUE, effectively not limiting the number of concurrent statements.

Parameters:

maxConcurrentWriteStatements - maximum number of write statements that can run concurrently.

Throws:

IllegalArgumentException - if the specified value is less than one.

IllegalStateException - if this object has already been initialized ( afterPropertiesSet() has been called).