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/*
 * Copyright Terracotta, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.ehcache.clustered.client.internal;

import org.ehcache.CachePersistenceException;
import org.ehcache.clustered.client.config.Timeouts;
import org.ehcache.clustered.client.config.builders.TimeoutsBuilder;
import org.ehcache.clustered.client.internal.lock.VoltronReadWriteLock;
import org.ehcache.clustered.client.internal.lock.VoltronReadWriteLock.Hold;
import org.ehcache.clustered.client.internal.store.ClusterTierClientEntity;
import org.ehcache.clustered.client.internal.store.ClusterTierUserData;
import org.ehcache.clustered.client.internal.store.InternalClusterTierClientEntity;
import org.ehcache.clustered.client.service.EntityBusyException;
import org.ehcache.clustered.common.ServerSideConfiguration;
import org.ehcache.clustered.common.internal.ClusterTierManagerConfiguration;
import org.ehcache.clustered.common.internal.ServerStoreConfiguration;
import org.ehcache.clustered.common.internal.exceptions.ClusterException;
import org.ehcache.clustered.common.internal.exceptions.DestroyInProgressException;
import org.ehcache.clustered.common.internal.store.ClusterTierEntityConfiguration;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.terracotta.connection.Connection;
import org.terracotta.connection.entity.EntityRef;
import org.terracotta.exception.EntityAlreadyExistsException;
import org.terracotta.exception.EntityConfigurationException;
import org.terracotta.exception.EntityException;
import org.terracotta.exception.EntityNotFoundException;
import org.terracotta.exception.EntityNotProvidedException;
import org.terracotta.exception.EntityVersionMismatchException;
import org.terracotta.exception.PermanentEntityException;

import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeoutException;

import static org.ehcache.clustered.common.EhcacheEntityVersion.ENTITY_VERSION;

public class ClusterTierManagerClientEntityFactory {

  private static final Logger LOGGER = LoggerFactory.getLogger(ClusterTierManagerClientEntityFactory.class);

  private final Connection connection;
  private final Map maintenanceHolds = new ConcurrentHashMap<>();
  private final Map fetchHolds = new ConcurrentHashMap<>();

  private final Timeouts entityTimeouts;

  public ClusterTierManagerClientEntityFactory(Connection connection) {
    this(connection, TimeoutsBuilder.timeouts().build());
  }

  public ClusterTierManagerClientEntityFactory(Connection connection, Timeouts entityTimeouts) {
    this.connection = connection;
    this.entityTimeouts = entityTimeouts;
  }

  public boolean acquireLeadership(String entityIdentifier) {
    VoltronReadWriteLock lock = createAccessLockFor(entityIdentifier);

    Hold hold = lock.tryWriteLock();
    if (hold == null) {
      return false;
    } else {
      maintenanceHolds.put(entityIdentifier, hold);
      return true;
    }
  }

  public boolean abandonAllHolds(String entityIdentifier, boolean healthyConnection) {
    return abandonLeadership(entityIdentifier, healthyConnection) | abandonFetchHolds(entityIdentifier, healthyConnection);
  }

  /**
   * Proactively abandon leadership before closing connection.
   *
   * @param entityIdentifier the master entity identifier
   * @return true of abandoned false otherwise
   */
  public boolean abandonLeadership(String entityIdentifier, boolean healthyConnection) {
    Hold hold = maintenanceHolds.remove(entityIdentifier);
    return (hold != null) && healthyConnection && silentlyUnlock(hold, entityIdentifier);
  }

  /**
   * Proactively abandon any READ holds before closing connection.
   *
   * @param entityIdentifier the master entity identifier
   * @return true of abandoned false otherwise
   */
  private boolean abandonFetchHolds(String entityIdentifier, boolean healthyConnection) {
    Hold hold = fetchHolds.remove(entityIdentifier);
    return (hold != null) && healthyConnection && silentlyUnlock(hold, entityIdentifier);
  }

  /**
   * Attempts to create and configure the {@code EhcacheActiveEntity} in the Ehcache clustered server.
   *
   * @param identifier the instance identifier for the {@code EhcacheActiveEntity}
   * @param config the {@code EhcacheActiveEntity} configuration to use for creation
   *
   * @throws EntityAlreadyExistsException if the {@code EhcacheActiveEntity} for {@code identifier} already exists
   * @throws ClusterTierManagerCreationException if an error preventing {@code EhcacheActiveEntity} creation was raised
   * @throws EntityBusyException if another client holding operational leadership prevented this client
   *        from becoming leader and creating the {@code EhcacheActiveEntity} instance
   */
  public void create(final String identifier, final ServerSideConfiguration config)
    throws EntityAlreadyExistsException, ClusterTierManagerCreationException, EntityBusyException {

    Hold existingMaintenance = maintenanceHolds.get(identifier);

    try(Hold localMaintenance = (existingMaintenance == null ? createAccessLockFor(identifier).tryWriteLock() : null)) {
      if (localMaintenance == null && existingMaintenance == null) {
        throw new EntityBusyException("Unable to obtain maintenance lease for " + identifier);
      }

      EntityRef ref = getEntityRef(identifier);
      try {
        ref.create(new ClusterTierManagerConfiguration(identifier, config));
      } catch (EntityConfigurationException e) {
        throw new ClusterTierManagerCreationException("Unable to configure cluster tier manager for id " + identifier, e);
      } catch (EntityNotProvidedException | EntityVersionMismatchException e) {
        LOGGER.error("Unable to create cluster tier manager for id {}", identifier, e);
        throw new AssertionError(e);
      }
    }
  }

  /**
   * Attempts to retrieve a reference to an existing {@code EhcacheActiveEntity} in an Ehcache clustered server.
   *
   * @param identifier the instance identifier for the {@code EhcacheActiveEntity}
   * @param config the {@code EhcacheActiveEntity} configuration to use for access checking
   *
   * @return an {@code ClusterTierManagerClientEntity} providing access to the {@code EhcacheActiveEntity} identified by
   *      {@code identifier}
   *
   * @throws EntityNotFoundException if the {@code EhcacheActiveEntity} identified as {@code identifier} does not exist
   * @throws IllegalArgumentException if {@code config} does not match the {@code EhcacheActiveEntity} configuration
   * @throws TimeoutException if the creation and configuration of the {@code EhcacheActiveEntity} exceed the
   *        lifecycle operation timeout
   */
  public ClusterTierManagerClientEntity retrieve(String identifier, ServerSideConfiguration config)
    throws DestroyInProgressException, EntityNotFoundException, ClusterTierManagerValidationException, TimeoutException {

    Hold fetchHold = createAccessLockFor(identifier).readLock();

    ClusterTierManagerClientEntity entity;
    try {
      entity = getEntityRef(identifier).fetchEntity(null);
    } catch (EntityVersionMismatchException e) {
      LOGGER.error("Unable to retrieve cluster tier manager for id {}", identifier, e);
      silentlyUnlock(fetchHold, identifier);
      throw new AssertionError(e);
    }

    boolean validated = false;
    try {
      entity.validate(config);
      validated = true;
      return entity;
    } catch (DestroyInProgressException e) {
      throw e;
    } catch (ClusterException e) {
      throw new ClusterTierManagerValidationException("Unable to validate cluster tier manager for id " + identifier, e);
    } finally {
      if (!validated) {
        silentlyClose(entity, identifier);
        silentlyUnlock(fetchHold, identifier);
      } else {
        // track read holds as well so that we can explicitly abandon
        fetchHolds.put(identifier, fetchHold);
      }
    }
  }

  public void destroy(final String identifier) throws EntityBusyException {
    Hold existingMaintenance = maintenanceHolds.get(identifier);

    try(Hold localMaintenance = (existingMaintenance == null ? createAccessLockFor(identifier).tryWriteLock() : null)) {
      if (localMaintenance == null && existingMaintenance == null) {
        throw new EntityBusyException("Unable to obtain maintenance lease for " + identifier);
      }

      EntityRef ref = getEntityRef(identifier);
      destroyAllClusterTiers(ref, identifier);
      try {
        if (!ref.destroy()) {
          throw new EntityBusyException("Destroy operation failed; " + identifier + " cluster tier in use by other clients");
        }
      } catch (EntityNotProvidedException e) {
        LOGGER.error("Unable to delete cluster tier manager for id {}", identifier, e);
        throw new AssertionError(e);
      } catch (EntityNotFoundException e) {
        // Ignore - entity does not exist
      } catch (PermanentEntityException e) {
        LOGGER.error("Unable to destroy entity - server says it is permanent", e);
        throw new AssertionError(e);
      }
    }
  }

  private void destroyAllClusterTiers(EntityRef ref, String identifier) {
    ClusterTierManagerClientEntity entity;
    try {
      entity = ref.fetchEntity(null);
    } catch (EntityNotFoundException e) {
      // Ignore - means entity does not exist
      return;
    } catch (EntityVersionMismatchException e) {
      throw new AssertionError(e);
    }
    Set storeIdentifiers = entity.prepareForDestroy();
    LOGGER.warn("Preparing to destroy stores {}", storeIdentifiers);
    for (String storeIdentifier : storeIdentifiers) {
      try {
        destroyClusteredStoreEntity(identifier, storeIdentifier);
      } catch (EntityNotFoundException e) {
        // Ignore - assume it was deleted already
      } catch (CachePersistenceException e) {
        throw new AssertionError("Unable to destroy cluster tier - in use: " + e.getMessage());
      }
    }
    entity.close();
  }

  private void silentlyClose(ClusterTierManagerClientEntity entity, String identifier) {
    try {
      entity.close();
    } catch (Exception e) {
      LOGGER.error("Failed to close entity {}", identifier, e);
    }
  }

  private boolean silentlyUnlock(Hold localMaintenance, String identifier) {
    try {
      localMaintenance.unlock();
      return true;
    } catch(Exception e) {
      LOGGER.error("Failed to unlock for id {}", identifier, e);
      return false;
    }
  }

  private VoltronReadWriteLock createAccessLockFor(String entityIdentifier) {
    return new VoltronReadWriteLock(connection, "ClusterTierManagerClientEntityFactory-AccessLock-" + entityIdentifier);
  }

  private EntityRef getEntityRef(String identifier) {
    try {
      return connection.getEntityRef(ClusterTierManagerClientEntity.class, ENTITY_VERSION, identifier);
    } catch (EntityNotProvidedException e) {
      LOGGER.error("Unable to get cluster tier manager for id {}", identifier, e);
      throw new AssertionError(e);
    }
  }

  public ClusterTierClientEntity fetchOrCreateClusteredStoreEntity(String clusterTierManagerIdentifier,
                                                                   String storeIdentifier, ServerStoreConfiguration clientStoreConfiguration,
                                                                   boolean autoCreate) throws EntityNotFoundException, CachePersistenceException {
    EntityRef entityRef;
    try {
      entityRef = connection.getEntityRef(InternalClusterTierClientEntity.class, ENTITY_VERSION, entityName(clusterTierManagerIdentifier, storeIdentifier));
    } catch (EntityNotProvidedException e) {
      throw new AssertionError(e);
    }

    if (autoCreate) {
      while (true) {
        try {
          entityRef.create(new ClusterTierEntityConfiguration(clusterTierManagerIdentifier, storeIdentifier, clientStoreConfiguration));
        } catch (EntityAlreadyExistsException e) {
          // Ignore - entity exists
        } catch (EntityConfigurationException e) {
          throw new CachePersistenceException("Unable to create cluster tier", e);
        } catch (EntityException e) {
          throw new AssertionError(e);
        }
        try {
          return entityRef.fetchEntity(new ClusterTierUserData(entityTimeouts, storeIdentifier));
        } catch (EntityNotFoundException e) {
          // Ignore - will try to create again
        } catch (EntityException e) {
          throw new AssertionError(e);
        }
      }
    } else {
      return fetchClusterTierClientEntity(storeIdentifier, entityRef);
    }
  }

  public ClusterTierClientEntity getClusterTierClientEntity(String clusterTierManagerIdentifier, String storeIdentifier) throws EntityNotFoundException {
    EntityRef entityRef;
    try {
      entityRef = connection.getEntityRef(InternalClusterTierClientEntity.class, ENTITY_VERSION, entityName(clusterTierManagerIdentifier, storeIdentifier));
    } catch (EntityNotProvidedException e) {
      throw new AssertionError(e);
    }

    return fetchClusterTierClientEntity(storeIdentifier, entityRef);
  }

  private ClusterTierClientEntity fetchClusterTierClientEntity(String storeIdentifier,
                                  EntityRef entityRef)
    throws EntityNotFoundException {
    try {
      return entityRef.fetchEntity(new ClusterTierUserData(entityTimeouts, storeIdentifier));
    } catch (EntityNotFoundException e) {
      throw e;
    } catch (EntityException e) {
      throw new AssertionError(e);
    }
  }

  public void destroyClusteredStoreEntity(String clusterTierManagerIdentifier, String storeIdentifier) throws EntityNotFoundException, CachePersistenceException {
    EntityRef entityRef;
    try {
      entityRef = connection.getEntityRef(InternalClusterTierClientEntity.class, ENTITY_VERSION, entityName(clusterTierManagerIdentifier, storeIdentifier));
      if (!entityRef.destroy()) {
        throw new CachePersistenceException("Cannot destroy cluster tier '" + storeIdentifier + "': in use by other client(s)");
      }
    } catch (EntityNotProvidedException | PermanentEntityException e) {
      throw new AssertionError(e);
    }
  }

  private static String entityName(String clusterTierManagerIdentifier, String storeIdentifier) {
    return clusterTierManagerIdentifier + "$" + storeIdentifier;
  }

  // For test purposes
  public Map getMaintenanceHolds() {
    return maintenanceHolds;
  }
}




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