com.aquenos.cassandra.pvarchiver.server.database

Class ClusterServersDAOImpl

java.lang.Object

com.aquenos.cassandra.pvarchiver.server.database.ClusterServersDAOImpl

All Implemented Interfaces:

ClusterServersDAO, Aware, SmartInitializingSingleton, ApplicationEventPublisherAware

public class ClusterServersDAOImpl
extends Object
implements ApplicationEventPublisherAware, ClusterServersDAO, SmartInitializingSingleton

Implementation of the data access object for accessing the servers within the archiving cluster. This object encapsulates the logic for accessing the cluster_servers table in the Apache Cassandra database.

Author:

Sebastian Marsching

Nested Class Summary

Nested classes/interfaces inherited from interface com.aquenos.cassandra.pvarchiver.server.database.ClusterServersDAO

ClusterServersDAO.ClusterServer

Field Summary

Fields

Modifier and Type	Field and Description
protected org.slf4j.Logger	log Logger for this object.

Constructor Summary

Constructors

Constructor and Description
ClusterServersDAOImpl()

Method Summary

Modifier and Type	Method and Description
void	afterSingletonsInstantiated()
ListenableFuture<Void>	createOrUpdateServer(UUID serverId, String serverName, String interNodeCommunicationUrl, Date lastOnlineTime) Creates or updates the record for an archive server.
ListenableFuture<Void>	deleteServer(UUID serverId) Removes the server with the specified ID from the database.
ListenableFuture<? extends ClusterServersDAO.ClusterServer>	getServer(UUID serverId) Reads the server object for the specified ID from the database.
ListenableFuture<? extends Iterable<? extends ClusterServersDAO.ClusterServer>>	getServers() Reads the server objects for all servers from the database.
boolean	isInitialized() Tells whether this DAO has finished initialization and is ready to be used.
void	onCassandraProviderInitializedEvent(CassandraProviderInitializedEvent event) Handles CassandraProviderInitializedEvents.
void	setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher)
void	setCassandraProvider(CassandraProvider cassandraProvider) Sets the Cassandra provider that provides access to the Apache Cassandra database.
ListenableFuture<Void>	updateServerLastOnlineTime(UUID serverId, Date lastOnlineTime) Updates the last-online time for an archive server.

Methods inherited from class java.lang.Object

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

Field Detail

log

protected final org.slf4j.Logger log

Logger for this object. The logger uses the actual type of this object and the base type where this field is declared.

Constructor Detail

ClusterServersDAOImpl

public ClusterServersDAOImpl()

Method Detail

onCassandraProviderInitializedEvent

@EventListener
 @Order(value=1000)
public void onCassandraProviderInitializedEvent(CassandraProviderInitializedEvent event)

Handles CassandraProviderInitializedEvents. This event is used when the CassandraProvider set using setCassandraProvider(CassandraProvider) is not ready yet when this object is initialized. In this case, some actions that usually are performed during initialization (like creating tables, initializing access objects) have to be deferred until the Apache Cassandra database becomes available.

Parameters:

event - initialization event sent by the CassandraProvider.

setCassandraProvider

@Autowired
public void setCassandraProvider(CassandraProvider cassandraProvider)

Sets the Cassandra provider that provides access to the Apache Cassandra database.

Parameters:

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

afterSingletonsInstantiated

public void afterSingletonsInstantiated()

Specified by:

afterSingletonsInstantiated in interface SmartInitializingSingleton

setApplicationEventPublisher

public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher)

Specified by:

setApplicationEventPublisher in interface ApplicationEventPublisherAware

createOrUpdateServer

public ListenableFuture<Void> createOrUpdateServer(UUID serverId,
                                                   String serverName,
                                                   String interNodeCommunicationUrl,
                                                   Date lastOnlineTime)

Description copied from interface: ClusterServersDAO

Creates or updates the record for an archive server. If the record for the specified serverId does not exist yet, it is created. Otherwise, it is updated. The operation is performed in an asynchronous way so that it will not block for network communication. The result of the operation can be checked through the returned future.

Specified by:

createOrUpdateServer in interface ClusterServersDAO

Parameters:

serverId - unique ID identifying the server within the cluster. This ID must be different for each server.

serverName - name (typically the hostname) of the server. The name is used to help the user in identifying a server. It should be unique for each server, but this condition is not enforced.

interNodeCommunicationUrl - base URL for the web-service interface of the server that can be used by other servers within the cluster to communicate with the server.

lastOnlineTime - time the server last updated its status. This time is used by other servers to determine if the server is online. Typically, this parameter should be the current time when calling this method. The last-online time needs to be updated periodically, but the ClusterServersDAO.updateServerLastOnlineTime(UUID, Date) should be preferred for this purpose.

Returns:

a future that can be used to check whether this operation finished and whether it was successful. In case of failure, the future's get() method will throw an exception.

deleteServer

public ListenableFuture<Void> deleteServer(UUID serverId)

Description copied from interface: ClusterServersDAO

Removes the server with the specified ID from the database. If the database does not store information for the specified ID, the operation will still succeed. The operation is performed in an asynchronous way so that it will not block for network communication. The result of the operation can be checked through the returned future.

Specified by:

deleteServer in interface ClusterServersDAO

Parameters:

serverId - unique identifier of the server that shall be removed from the database.

Returns:

future that can be used to check whether this operation finished and whether it was successful. In case of failure, the future's get() method will throw an exception.

getServer

public ListenableFuture<? extends ClusterServersDAO.ClusterServer> getServer(UUID serverId)

Description copied from interface: ClusterServersDAO

Reads the server object for the specified ID from the database. The object is not returned directly but through a listenable future, so that the calling code can wait for the database operation to finish asynchronously.

Specified by:

getServer in interface ClusterServersDAO

Parameters:

serverId - unique identifier identifying the server.

Returns:

a future providing access to the server object with the specified ID. If the database does not contain information for the specified ID, the future's get method returns null. In case of failure, the future's get() method will throw an exception.

getServers

public ListenableFuture<? extends Iterable<? extends ClusterServersDAO.ClusterServer>> getServers()

Description copied from interface: ClusterServersDAO

Reads the server objects for all servers from the database. The server objects are not returned directly but through a listenable future, so that the calling code can wait for the database operation to finish asynchronously.

The iterable returned by the future is only safe for iterating once. Subsequent requests to create an iterator might result in the new iterator only returning the elements that have not been returned by a previously created iterator yet. Besides, the iterator might block while iterating, waiting for additional elements to arrive from the network.

Specified by:

getServers in interface ClusterServersDAO

Returns:

a future providing access to the server objects representing all servers within the archiving cluster. In case of failure, the future's get() method will throw an exception.

isInitialized

public boolean isInitialized()

Description copied from interface: ClusterServersDAO

Tells whether this DAO has finished initialization and is ready to be used. Even if this method returns true, operations might still fail because of transient problems.

Specified by:

isInitialized in interface ClusterServersDAO

Returns:

true if this DAO has been initialized and is ready to be used, false if initialization has not completed yet.

updateServerLastOnlineTime

public ListenableFuture<Void> updateServerLastOnlineTime(UUID serverId,
                                                         Date lastOnlineTime)

Description copied from interface: ClusterServersDAO

Updates the last-online time for an archive server. This method should only be used if the record for the server has already been created using the ClusterServersDAO.createOrUpdateServer(UUID, String, String, Date) method. However, implementations might not enforce this limitation, silently creating a partially initialized record when this method is called first.

Specified by:

updateServerLastOnlineTime in interface ClusterServersDAO

Parameters:

serverId - unique ID identifying the server within the cluster. This ID must be different for each server.

lastOnlineTime - time the server last updated its status. This time is used by other servers to determine if the server is online. Typically, this parameter should be the current time when calling this method. The last-online time needs to be updated periodically.

Returns:

a future that can be used to check whether this operation finished and whether it was successful. In case of failure, the future's get() method will throw an exception.