com.aquenos.cassandra.pvarchiver.server.archiving

Class ArchivingService

java.lang.Object

com.aquenos.cassandra.pvarchiver.server.archiving.ArchivingService

All Implemented Interfaces:

DisposableBean, InitializingBean, SmartInitializingSingleton

public class ArchivingService
extends Object
implements DisposableBean, InitializingBean, SmartInitializingSingleton

Service performing the actual archiving. This service gets the list of channels registered with this server when the server goes online and starts archiving for these channels. It stops archiving when the server goes offline. The configuration of individual channels can be reloaded using the refreshChannel(String) method.

Author:

Sebastian Marsching

Constructor Summary

Constructors

Constructor and Description
ArchivingService()

Method Summary

Modifier and Type	Method and Description
void	afterPropertiesSet()
void	afterSingletonsInstantiated()
void	destroy()
ChannelStatus	getChannelStatus(String channelName) Returns the status of an archived channel.
List<ChannelStatus>	getChannelStatusForAllChannels() Returns a list of the status for all channels known by this archiving service.
long	getNumberOfSamplesDropped() Returns the total number of samples that have been dropped.
long	getNumberOfSamplesWritten() Returns the total number of samples that have been written.
void	onServerOnlineStatusEvent(ServerOnlineStatusEvent event) Notifies the archiving service that the server's online status changed.
ListenableFuture<Void>	refreshChannel(String channelName) Reloads the configuration of the specified channel.
void	setArchiveAccessService(ArchiveAccessService archiveAccessService) Sets the archive access service that is used to read samples from the database.
void	setCassandraProvider(CassandraProvider cassandraProvider) Sets the Cassandra provider that provides access to the Apache Cassandra database.
void	setChannelMetaDataDAO(ChannelMetaDataDAO channelMetaDataDAO) Sets the DAO for reading and modifying meta-data related to channels.
void	setClusterManagementService(ClusterManagementService clusterManagementService) Sets the cluster management service.
void	setControlSystemSupportRegistry(ControlSystemSupportRegistry controlSystemSupportRegistry) Sets the control-system support registry.
void	setServerProperties(ServerProperties serverProperties) Sets the server-specific configuration properties.

Methods inherited from class java.lang.Object

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

Constructor Detail

ArchivingService

public ArchivingService()

Method Detail

afterPropertiesSet

public void afterPropertiesSet()
                        throws Exception

Specified by:

afterPropertiesSet in interface InitializingBean

Throws:

Exception

afterSingletonsInstantiated

public void afterSingletonsInstantiated()

Specified by:

afterSingletonsInstantiated in interface SmartInitializingSingleton

destroy

public void destroy()
             throws Exception

Specified by:

destroy in interface DisposableBean

Throws:

Exception

getChannelStatus

public ChannelStatus getChannelStatus(String channelName)

Returns the status of an archived channel. If the channel is not known by this archiving service, null is returned. Throws an IllegalStateException if the archiving service has not finished initialization of its channel list yet.

Parameters:

channelName - name of the channel to be queried.

Returns:

status of the specified channel or null if the specified channel is not known by this archiving service.

Throws:

IllegalStateException - if the archiving service has not initialized its list of channels yet.

getChannelStatusForAllChannels

public List<ChannelStatus> getChannelStatusForAllChannels()

Returns a list of the status for all channels known by this archiving service. Throws an IllegalStateException if the archiving service has not finished initialization of its channel list yet. The channels are returned in the natural order of their names. The returned list is never null, but it might be empty if no channels belong this server.

Returns:

status of all channels known by this archiving service.

Throws:

IllegalStateException - if the archiving service has not initialized its list f channels yet.

getNumberOfSamplesDropped

public long getNumberOfSamplesDropped()

Returns the total number of samples that have been dropped. A sample is dropped when new samples for a channel arrive more quickly than they can be written and consequently samples remain in the queue until a timeout is reached. The returned number represents the total number of samples that have been dropped for any channel since this archiving service was started. When this number grows constantly, this can be an indication that the server (or the Cassandra cluster) is overloaded and the workload should be reduced (possibly by adding more servers).

Returns:

number of samples that have been dropped since this archiving service was started.

getNumberOfSamplesWritten

public long getNumberOfSamplesWritten()

Returns the total number of samples that have been written. A sample is only counted as written when the databases acknowledges that the write operation has been successful. Samples for all decimation levels and not just raw samples contribute to this number. The returned number represents the total number of samples that have been written since this archiving service was started.

Returns:

number of samples that have been written since this archiving service was started.

onServerOnlineStatusEvent

@EventListener
public void onServerOnlineStatusEvent(ServerOnlineStatusEvent event)

Notifies the archiving service that the server's online status changed. Typically, this method is automatically called by the Spring container when the ClusterManagementService publishes ServerOnlineStatusEvent.

This method takes care of starting archiving when the server goes online and stopping it when the server goes offline. These operations are performed asynchronously so that the thread sending the notification does not block.

Parameters:

event - event specifying the server's new online status.

refreshChannel

public ListenableFuture<Void> refreshChannel(String channelName)

Reloads the configuration of the specified channel. This method should be called whenever the configuration of a channel belonging to this server has been changed. It also needs to be called after registering a pending operation for a channel, so that archiving for the channel can be disabled.

If the server is currently offline, calling this method will typically have no effect because there is no need to reload the channel configuration. In this case, the future returned by this method completed immediately.

The future returned by this method completes when the refresh operation has finished. It should never throw an exception.

Parameters:

channelName - name of the channel to be refreshed.

Returns:

future that completes when the refresh operation has finished.

Throws:

NullPointerException - if channelName is null.

setArchiveAccessService

@Autowired
public void setArchiveAccessService(ArchiveAccessService archiveAccessService)

Sets the archive access service that is used to read samples from the database. When generating decimated samples, the archiving service might have to read samples that have been written earlier. It uses the archive access service for this purpose. Typically, this method is called automatically by the Spring container.

Parameters:

archiveAccessService - archive access service used for reading samples when generating decimated samples.

setCassandraProvider

@Autowired
public void setCassandraProvider(CassandraProvider cassandraProvider)

Sets the Cassandra provider that provides access to the Apache Cassandra database. Typically, this method is called automatically by the Spring container.

Parameters:

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

setChannelMetaDataDAO

@Autowired
public void setChannelMetaDataDAO(ChannelMetaDataDAO channelMetaDataDAO)

Sets the DAO for reading and modifying meta-data related to channels. The archiving services uses this DAO to read the configuration for archived channels and create the meta-data for new sample buckets when needed. Typically, this method is called automatically by the Spring container.

Parameters:

channelMetaDataDAO - channel meta-data DAO to be used by this object.

setClusterManagementService

@Autowired
public void setClusterManagementService(ClusterManagementService clusterManagementService)

Sets the cluster management service. The cluster management service is used to get information about the cluster status. In particular, it is needed to determine the online state of this server in order to now when archiving should be started and stopped. Typically, this method is called automatically by the Spring container.

Parameters:

clusterManagementService - cluster manager used by the archiving server.

setControlSystemSupportRegistry

@Autowired
public void setControlSystemSupportRegistry(ControlSystemSupportRegistry controlSystemSupportRegistry)

Sets the control-system support registry. The registry is used to gain access to the control-system supports available on this archiving server. Typically, this method is called automatically by the Spring container.

Parameters:

controlSystemSupportRegistry - control-system support registry for this archiving server.

setServerProperties

@Autowired
public void setServerProperties(ServerProperties serverProperties)

Sets the server-specific configuration properties. These server properties are used to get the ID of this archiving server.

Parameters:

serverProperties - configuration properties used by this server.