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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.clustercontroller.core.database;
import com.yahoo.vdslib.state.Node;
import com.yahoo.vdslib.state.NodeState;
import com.yahoo.vespa.clustercontroller.core.ClusterStateBundle;
import java.util.Map;
/**
* Abstract class defining the functions needed by a database back end for the fleetcontroller.
*/
public abstract class Database {
/** Interface used for database to send events of stuff happening during requests. */
public interface DatabaseListener {
void handleZooKeeperSessionDown();
void handleMasterData(Map<Integer, Integer> data);
}
/**
* Close this session, and release all resources it has used.
*/
public abstract void close();
/**
* @return True if the database is closed, and cannot be used anymore.
*/
public abstract boolean isClosed();
/**
* Set our vote for master election. Should always be set as this is the ephemeral node used for other
* fleetcontrollers to see that we are alive.
*
* @return True if request succeeded. False if not.
*/
public abstract boolean storeMasterVote(int wantedMasterIndex);
/**
* Store the latest system state version used. When the fleetcontroller makes a given version official it should
* store the version in the database, such that if another fleetcontroller takes over as master it will use a
* higher version system state.
*
* Precondition: retrieveLatestSystemStateVersion() MUST have been called at least once prior to calling
* this method.
*
* @return True if request succeeded. False if not.
* @throws CasWriteFailed if the expected version of the znode did not match what was actually stored in the DB.
* In this case, the write has NOT been applied.
*/
public abstract boolean storeLatestSystemStateVersion(int version);
/**
* Get the latest system state version used. To keep the version rising, a newly elected master will call this
* function to see at what index it should start.
*
* @return The last system state version used, or null if request failed.
*/
public abstract Integer retrieveLatestSystemStateVersion();
/**
* Save our current wanted states in the database. Typically called after processing an RPC request for altering
* a wanted state, or if the fleetcontroller decides to alter the wanted state itself.
*
* @return True if the request succeeded. False if not.
*/
public abstract boolean storeWantedStates(Map<Node, NodeState> states);
/**
* Read wanted states from the database and set wanted states for all nodes in the cluster accordingly.
* This function is typically called when one take over as master fleetcontroller.
*
* @return True if wanted states was altered, false if not. Null if request failed.
*/
public abstract Map<Node, NodeState> retrieveWantedStates();
/**
* Store start times of distributor and service layer nodes in zookeeper.
*/
public abstract boolean storeStartTimestamps(Map<Node, Long> timestamps);
/**
* Fetch the start times of distributor and service layer nodes.
*/
public abstract Map<Node, Long> retrieveStartTimestamps();
/**
* Stores the last published cluster state bundle synchronously into ZooKeeper.
*
* Precondition: retrieveLastPublishedStateBundle() MUST have been called at least once prior to calling
* this method.
*
* @return true if the write is known to have been successful, false otherwise. If false is returned, the
* write may or may not have taken place.
* @throws CasWriteFailed if the expected version of the znode did not match what was actually stored in the DB.
* In this case, the write has NOT been applied.
*/
public abstract boolean storeLastPublishedStateBundle(ClusterStateBundle stateBundle);
public abstract ClusterStateBundle retrieveLastPublishedStateBundle();
}
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