com.aquenos.cassandra.pvarchiver.server.archiving

Class ChannelInformationCacheImpl

java.lang.Object

com.aquenos.cassandra.pvarchiver.server.archiving.ChannelInformationCacheImpl

All Implemented Interfaces:

ChannelInformationCache, DisposableBean, InitializingBean, SmartInitializingSingleton

public class ChannelInformationCacheImpl
extends Object
implements ChannelInformationCache, DisposableBean, InitializingBean, SmartInitializingSingleton

Standard implementation of the ChannelInformationCache.

Author:

Sebastian Marsching

Field Summary

Fields

Modifier and Type	Field and Description
protected org.apache.commons.logging.Log	log Logger for this class.

Constructor Summary

Constructors

Constructor and Description
ChannelInformationCacheImpl()

Method Summary

Modifier and Type	Method and Description
void	afterPropertiesSet()
void	afterSingletonsInstantiated()
void	destroy()
ChannelMetaDataDAO.ChannelInformation	getChannel(String channelName) Returns the channel information for the specified channel name or null if the channel does not exist.
ListenableFuture<ChannelMetaDataDAO.ChannelInformation>	getChannelAsync(String channelName, boolean forceUpdate) Returns the channel information for the specified channel name or null if the channel does not exist.
SortedMap<String,ChannelMetaDataDAO.ChannelInformation>	getChannels() Returns a map containing all channels in the cluster.
SortedMap<String,ChannelMetaDataDAO.ChannelInformation>	getChannels(UUID serverId) Returns a map containing all channels for the specified server.
Map<UUID,SortedMap<String,ChannelMetaDataDAO.ChannelInformation>>	getChannelsSortedByServer() Returns a map containing all channels in the cluster.
void	onServerOnlineStatusEvent(ServerOnlineStatusEvent event) Notifies the channel information cache that the server's online status changed.
ListenableFuture<Void>	processUpdate(List<ChannelMetaDataDAO.ChannelInformation> channelInformationUpdates, List<String> missingChannels, Iterable<UUID> forwardToServers, long remoteTime) Process an update that has been received from a remote server.
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	setInterNodeCommunicationService(InterNodeCommunicationService interNodeCommunicationService) Sets the inter-node communication service.
ListenableFuture<Void>	updateChannels(Iterable<String> channelNames) Updates the channel information for the specified channel name.

Methods inherited from class java.lang.Object

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

Field Detail

log

protected final org.apache.commons.logging.Log log

Logger for this class.

Constructor Detail

ChannelInformationCacheImpl

public ChannelInformationCacheImpl()

Method Detail

setChannelMetaDataDAO

@Autowired
public void setChannelMetaDataDAO(ChannelMetaDataDAO channelMetaDataDAO)

Sets the DAO for reading and modifying meta-data related to channels. The channel information cache uses this DAO to read the information about channels whenever an update of the cache is 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 know when the cache should be updated or invalidated. Typically, this method is called automatically by the Spring container.

Parameters:

clusterManagementService - cluster manager used by the archiving server.

setInterNodeCommunicationService

@Autowired
public void setInterNodeCommunicationService(InterNodeCommunicationService interNodeCommunicationService)

Sets the inter-node communication service. The inter-node communication service is needed to send channel-information updates to other servers in the cluster.

Parameters:

interNodeCommunicationService - inter-node communication service.

onServerOnlineStatusEvent

@EventListener
public void onServerOnlineStatusEvent(ServerOnlineStatusEvent event)

Notifies the channel information cache 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 updating the cache when the server goes online and invalidating the cache 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.

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

getChannel

public ChannelMetaDataDAO.ChannelInformation getChannel(String channelName)

Description copied from interface: ChannelInformationCache

Returns the channel information for the specified channel name or null if the channel does not exist.

The cache works in a way that it should be updated when channels are modifies, so in general it should return up-to-date information about channels. However, due to the asynchronous nature of cache updates, it is possible that this method returns obsolete information. If it is important that the most up-to-date information is returned, the ChannelInformationCache.getChannelAsync(String, boolean) method should be preferred.

This method throws an IllegalStateException if the cache is not ready. Reasons for the cache not being ready might be that it has not been properly initialized yet or that updates have failed and thus the cache has been invalidated in order to avoid serving obsolete information.

Specified by:

getChannel in interface ChannelInformationCache

Parameters:

channelName - name of the channel for which the channel information shall be retrieved.

Returns:

channel information for the specified channel name or null if the channel does not exist.

getChannelAsync

public ListenableFuture<ChannelMetaDataDAO.ChannelInformation> getChannelAsync(String channelName,
                                                                               boolean forceUpdate)

Description copied from interface: ChannelInformationCache

Returns the channel information for the specified channel name or null if the channel does not exist. The operation completes asynchronously (without blocking), so the channel information is returned through a future.

If the cache is not ready to be queried, this method queries the database directly. If the forceUpdate flag is true, the database is always queried directly and the information in the cache is updated with the information retrieved from the database.

The future returned by this method might throw the following exceptions:

• NullPointerException if the channelName is null.
• RuntimeException if the database is queried and that query fails.

Specified by:

getChannelAsync in interface ChannelInformationCache

Parameters:

channelName - name of the channel for which the channel information shall be retrieved.

forceUpdate - true if the database shall always be queried, even if the cache is ready. false if the information from the cache should be used if the cache is ready.

Returns:

channel information for the specified channel name, exposed through a listenable future.

getChannels

public SortedMap<String,ChannelMetaDataDAO.ChannelInformation> getChannels()

Description copied from interface: ChannelInformationCache

Returns a map containing all channels in the cluster. The channel names are used as keys and the corresponding channel information objects are stored as values.

All the information is served from the cache. The cache works in a way that it should be updated when channels are modifies, so in general it should return up-to-date information about channels. However, due to the asynchronous nature of cache updates, it is possible that this method returns obsolete information.

This method throws an IllegalStateException if the cache is not ready. Reasons for the cache not being ready might be that it has not been properly initialized yet or that updates have failed and thus the cache has been invalidated in order to avoid serving obsolete information.

Specified by:

getChannels in interface ChannelInformationCache

Returns:

map containing all channels that exist in the cluster.

getChannels

public SortedMap<String,ChannelMetaDataDAO.ChannelInformation> getChannels(UUID serverId)

Description copied from interface: ChannelInformationCache

Returns a map containing all channels for the specified server. The channel names are used as keys and the corresponding channel information objects are stored as values. If the specified server is unknown, an empty map is returned.

All the information is served from the cache. The cache works in a way that it should be updated when channels are modifies, so in general it should return up-to-date information about channels. However, due to the asynchronous nature of cache updates, it is possible that this method returns obsolete information.

This method throws an IllegalStateException if the cache is not ready. Reasons for the cache not being ready might be that it has not been properly initialized yet or that updates have failed and thus the cache has been invalidated in order to avoid serving obsolete information.

Specified by:

getChannels in interface ChannelInformationCache

Parameters:

serverId - id of the server for which the channels shall be returned.

Returns:

map containing all channels for the specified server.

getChannelsSortedByServer

public Map<UUID,SortedMap<String,ChannelMetaDataDAO.ChannelInformation>> getChannelsSortedByServer()

Description copied from interface: ChannelInformationCache

Returns a map containing all channels in the cluster. The channels are aggregated by their associated server, having one map for each server ID.

All the information is served from the cache. The cache works in a way that it should be updated when channels are modifies, so in general it should return up-to-date information about channels. However, due to the asynchronous nature of cache updates, it is possible that this method returns obsolete information.

This method throws an IllegalStateException if the cache is not ready. Reasons for the cache not being ready might be that it has not been properly initialized yet or that updates have failed and thus the cache has been invalidated in order to avoid serving obsolete information.

Specified by:

getChannelsSortedByServer in interface ChannelInformationCache

Returns:

map containing all channels that exist in the cluster aggregated by server. The returned map contains an entry for each known server that has at least one channel. Each of this entries has a map as its value that maps channel names to the corresponding channel information objects.

processUpdate

public ListenableFuture<Void> processUpdate(List<ChannelMetaDataDAO.ChannelInformation> channelInformationUpdates,
                                            List<String> missingChannels,
                                            Iterable<UUID> forwardToServers,
                                            long remoteTime)

Description copied from interface: ChannelInformationCache

Process an update that has been received from a remote server. This method should only be called by remote servers (through the corresponding web-service API). It updates the cache with the information supplied in the request, merging the entries in the cache with the entries from the update. The cache is updated synchronously, but the servers specified in forwardToServers are notified asynchronously.

The notification of other servers works in a cascaded way: Only a limited number of servers from the specified list are notified directly. Those servers are in turn asked to notify a subset of the remaining servers. This way, each server only has to handle a limited number of notifications, even if the cluster is very large.

The returned future throws a NullPointerException if channelInformationUpdates, missingChannels, or forwardToServers is null or they contain null elements.

Specified by:

processUpdate in interface ChannelInformationCache

Parameters:

channelInformationUpdates - updated channel-information objects.

missingChannels - channels that are missing now (the channel information is null - typically because the channel has been deleted).

forwardToServers - list of servers which should be notified with the information from the update.

remoteTime - time stamp (as returned by System.currentTimeMillis() of the point in time before the channel information that is sent with this update was retrieved from the database. This information is used when resolving conflicting updates for the same channel.

Returns:

listenable future that finishes when the cache has been updated and all servers have been notified (or the notification attempts have failed).

updateChannels

public ListenableFuture<Void> updateChannels(Iterable<String> channelNames)

Description copied from interface: ChannelInformationCache

Updates the channel information for the specified channel name. This method does not only update the local cache but also forwards the updated information to all remote servers by calling their ChannelInformationCache.processUpdate(List, List, Iterable, long) method with the updated information.

This method is intended for the ArchiveConfigurationService which calls it when it modifies channel configurations.

The future returned by this method might throw the following exceptions:

• NullPointerException if the channelNames is null or contains null elements.
• RuntimeException if one of the database queries needed for the update fails.

Specified by:

updateChannels in interface ChannelInformationCache

Parameters:

channelNames - names of the channels to be updated.

Returns:

listenable future that completes when the local cache has been updated and the update has been forwarded to the remote servers.