com.aquenos.cassandra.pvarchiver.server.database

Interface ClusterServersDAO

All Known Implementing Classes:

ClusterServersDAOImpl

public interface ClusterServersDAO

Data access object for accessing the servers within the archiving cluster.

Author:

Sebastian Marsching

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	ClusterServersDAO.ClusterServer Value object representing a server within the archiving cluster.

Method Summary

Modifier and Type	Method and Description
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.
ListenableFuture<Void>	updateServerLastOnlineTime(UUID serverId, Date lastOnlineTime) Updates the last-online time for an archive server.

Method Detail

createOrUpdateServer

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

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.

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 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

ListenableFuture<Void> deleteServer(UUID serverId)

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.

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

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

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.

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

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

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.

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

boolean isInitialized()

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.

Returns:

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

updateServerLastOnlineTime

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

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 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.

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.