content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements. See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You 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.apache.kafka.connect.storage;
  
  import org.apache.kafka.connect.runtime.RestartRequest;
  import org.apache.kafka.connect.runtime.SessionKey;
  import org.apache.kafka.connect.runtime.TargetState;
  import org.apache.kafka.connect.util.ConnectorTaskId;
  
  import java.util.Collection;
  import java.util.List;
  import java.util.Map;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.TimeoutException;
  
  /**
   * An interface to store and retrieve (via {@link #snapshot()}) configuration information that is created during
   * runtime (i.e. not static configuration like the {@link org.apache.kafka.connect.runtime.WorkerConfig worker config}).
   * This configuration information includes connector configs, task configs, connector target states etc.
   */
  public interface ConfigBackingStore {
  
      void start();
  
      void stop();
  
      /**
       * Get a snapshot of the current configuration state including all connector and task
       * configurations.
       * @return the cluster config state
       */
      ClusterConfigState snapshot();
  
      /**
       * Check if the store has configuration for a connector.
       * @param connector name of the connector
       * @return true if the backing store contains configuration for the connector
       */
      boolean contains(String connector);
  
      /**
       * Update the configuration for a connector.
       * @param connector name of the connector
       * @param properties the connector configuration
       * @param targetState the desired target state for the connector; may be {@code null} if no target state change is desired. Note that the default
       *                    target state is {@link TargetState#STARTED} if no target state exists previously
       */
      void putConnectorConfig(String connector, Map<String, String> properties, TargetState targetState);
  
      /**
       * Remove configuration for a connector
       * @param connector name of the connector
       */
      void removeConnectorConfig(String connector);
  
      /**
       * Update the task configurations for a connector.
       * @param connector name of the connector
       * @param configs the new task configs for the connector
       */
      void putTaskConfigs(String connector, List<Map<String, String>> configs);
  
      /**
       * Remove the task configs associated with a connector.
       * @param connector name of the connector
       */
      void removeTaskConfigs(String connector);
  
      /**
       * Refresh the backing store. This forces the store to ensure that it has the latest
       * configs that have been written.
       * @param timeout max time to wait for the refresh to complete
       * @param unit unit of timeout
       * @throws TimeoutException if the timeout expires before the refresh has completed
       */
      void refresh(long timeout, TimeUnit unit) throws TimeoutException;
  
      /**
       * Transition a connector to a new target state (e.g. paused).
       * @param connector name of the connector
       * @param state the state to transition to
       */
      void putTargetState(String connector, TargetState state);
  
      /**
       * Store a new {@link SessionKey} that can be used to validate internal (i.e., non-user-triggered) inter-worker communication.
       * @param sessionKey the session key to store
       */
      void putSessionKey(SessionKey sessionKey);
  
      /**
       * Request a restart of a connector and optionally its tasks.
       * @param restartRequest the restart request details
       */
      void putRestartRequest(RestartRequest restartRequest);
  
      /**
       * Record the number of tasks for the connector after a successful round of zombie fencing.
       * @param connector name of the connector
       * @param taskCount number of tasks used by the connector
       */
      void putTaskCountRecord(String connector, int taskCount);
  
      /**
       * Prepare to write to the backing config store. May be required by some implementations (such as those that only permit a single
       * writer at a time across a cluster of workers) before performing mutating operations like writing configurations, target states, etc.
       * The default implementation is a no-op; it is the responsibility of the implementing class to override this and document any expectations for
       * when it must be invoked.
       */
      default void claimWritePrivileges() {
      }
  
      /**
       * Emit a new level for the specified logging namespace (and all of its children). This level should
       * be applied by all workers currently in the cluster, but not to workers that join after it is stored.
       * @param namespace the namespace to adjust; may not be null
       * @param level the new level for the namespace; may not be null
       */
      void putLoggerLevel(String namespace, String level);
  
      /**
       * Set an update listener to get notifications when there are new records written to the backing store.
       * @param listener non-null listener
       */
      void setUpdateListener(UpdateListener listener);
  
      interface UpdateListener {
          /**
           * Invoked when a connector configuration has been removed
           * @param connector name of the connector
           */
          void onConnectorConfigRemove(String connector);
  
          /**
           * Invoked when a connector configuration has been updated.
           * @param connector name of the connector
           */
          void onConnectorConfigUpdate(String connector);
  
          /**
           * Invoked when task configs are updated.
           * @param tasks all the tasks whose configs have been updated
           */
          void onTaskConfigUpdate(Collection<ConnectorTaskId> tasks);
  
          /**
           * Invoked when the user has set a new target state (e.g. paused)
           * @param connector name of the connector
           */
          void onConnectorTargetStateChange(String connector);
  
          /**
           * Invoked when the leader has distributed a new session key
           * @param sessionKey the {@link SessionKey session key}
           */
          void onSessionKeyUpdate(SessionKey sessionKey);
  
          /**
           * Invoked when a connector and possibly its tasks have been requested to be restarted.
           * @param restartRequest the {@link RestartRequest restart request}
           */
          void onRestartRequest(RestartRequest restartRequest);
  
          /**
           * Invoked when a dynamic log level adjustment has been read
           * @param namespace the namespace to adjust; never null
           * @param level the level to set the namespace to; never null
           */
          void onLoggingLevelUpdate(String namespace, String level);
      }
  
  }
  