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.streams.processor.internals;
  
  import org.apache.kafka.common.Uuid;
  import org.apache.kafka.common.internals.KafkaFutureImpl;
  import org.apache.kafka.streams.processor.TaskId;
  
  import java.time.Duration;
  import java.util.List;
  import java.util.Objects;
  import java.util.Optional;
  import java.util.Set;
  import java.util.concurrent.CompletableFuture;
  
  public interface StateUpdater {
  
      class ExceptionAndTask {
          private final Task task;
          private final RuntimeException exception;
  
          public ExceptionAndTask(final RuntimeException exception, final Task task) {
              this.exception = Objects.requireNonNull(exception);
              this.task = Objects.requireNonNull(task);
          }
  
          public Task task() {
              return task;
          }
  
          public RuntimeException exception() {
              return exception;
          }
  
          @Override
          public boolean equals(final Object o) {
              if (this == o) return true;
              if (!(o instanceof ExceptionAndTask)) return false;
              final ExceptionAndTask that = (ExceptionAndTask) o;
              return task.id().equals(that.task.id()) && exception.equals(that.exception);
          }
  
          @Override
          public int hashCode() {
              return Objects.hash(task, exception);
          }
  
          @Override
          public String toString() {
              return "ExceptionAndTask{" +
                  "task=" + task.id() +
                  ", exception=" + exception +
                  '}';
          }
      }
  
      class RemovedTaskResult {
  
          private final Task task;
          private final Optional<RuntimeException> exception;
  
          public RemovedTaskResult(final Task task) {
              this(task, null);
          }
  
          public RemovedTaskResult(final Task task, final RuntimeException exception) {
              this.task = Objects.requireNonNull(task);
              this.exception = Optional.ofNullable(exception);
          }
  
          public Task task() {
              return task;
          }
  
          public Optional<RuntimeException> exception() {
              return exception;
          }
  
          @Override
          public boolean equals(final Object o) {
              if (this == o) return true;
              if (!(o instanceof RemovedTaskResult)) return false;
              final RemovedTaskResult that = (RemovedTaskResult) o;
              return Objects.equals(task.id(), that.task.id()) && Objects.equals(exception, that.exception);
          }
  
          @Override
          public int hashCode() {
              return Objects.hash(task, exception);
          }
  
          @Override
          public String toString() {
              return "RemovedTaskResult{" +
                  "task=" + task.id() +
                  ", exception=" + exception +
                  '}';
          }
      }
  
      /**
       * Starts the state updater.
       */
      void start();
  
      /**
       * Shuts down the state updater.
       *
       * @param timeout duration how long to wait until the state updater is shut down
       *
       * @throws
       *     org.apache.kafka.streams.errors.StreamsException if the state updater thread cannot shutdown within the timeout
       */
      void shutdown(final Duration timeout);
  
      /**
       * Adds a task (active or standby) to the state updater.
       *
       * This method does not block until the task is added to the state updater.
       *
       * @param task task to add
       */
      void add(final Task task);
  
      /**
       * Removes a task (active or standby) from the state updater.
       *
       * This method does not block until the removed task is removed from the state updater. But it returns a future on
       * which processing can be blocked. The task to remove is removed from the updating tasks, paused tasks,
       * restored tasks, or failed tasks.
       *
       * @param taskId ID of the task to remove
       */
      CompletableFuture<RemovedTaskResult> remove(final TaskId taskId);
  
      /**
       * Wakes up the state updater if it is currently dormant, to check if a paused task should be resumed.
       */
      void signalResume();
  
      /**
       * Drains the restored active tasks from the state updater.
       *
       * The returned active tasks are removed from the state updater.
       *
       * With a timeout of zero the method tries to drain the restored active tasks at least once.
       *
       * @param timeout duration how long the calling thread should wait for restored active tasks
       *
       * @return set of active tasks with up-to-date states
       */
      Set<StreamTask> drainRestoredActiveTasks(final Duration timeout);
  
      /**
       * Drains the failed tasks and the corresponding exceptions.
       *
       * The returned failed tasks are removed from the state updater
       *
       * @return list of failed tasks and the corresponding exceptions
       */
      List<ExceptionAndTask> drainExceptionsAndFailedTasks();
  
      /**
       * Checks if the state updater has any failed tasks that should be returned to the StreamThread
       * using `drainExceptionsAndFailedTasks`.
       *
       * @return true if a subsequent call to `drainExceptionsAndFailedTasks` would return a non-empty collection.
       */
      boolean hasExceptionsAndFailedTasks();
  
      /**
       * Gets all tasks that are managed by the state updater.
       *
       * The state updater manages all tasks that were added with the {@link StateUpdater#add(Task)} and that have
       * not been removed from the state updater with one of the following methods:
       * <ul>
       *   <li>{@link StateUpdater#drainRestoredActiveTasks(Duration)}</li>
       *   <li>{@link StateUpdater#drainExceptionsAndFailedTasks()}</li>
       *   <li>{@link StateUpdater#remove(org.apache.kafka.streams.processor.TaskId)}</li>
       * </ul>
       *
       * @return set of all tasks managed by the state updater
       */
      Set<Task> tasks();
  
      /**
       * Gets all tasks that are currently being restored inside the state updater.
       *
       * Tasks that have just being added into the state updater via {@link StateUpdater#add(Task)}
       * or have restored completely or removed will not be returned; tasks that have just being
       * removed via {@link StateUpdater#remove(TaskId)} may still be returned.
       *
       * @return set of all updating tasks inside the state updater
       */
      Set<Task> updatingTasks();
  
      /**
       * Returns if the state updater restores active tasks.
       *
       * The state updater restores active tasks if at least one active task was added with {@link StateUpdater#add(Task)},
       * and the task was not removed from the state updater with one of the following methods:
       * <ul>
       *   <li>{@link StateUpdater#drainRestoredActiveTasks(Duration)}</li>
       *   <li>{@link StateUpdater#drainExceptionsAndFailedTasks()}</li>
       *   <li>{@link StateUpdater#remove(org.apache.kafka.streams.processor.TaskId)}</li>
       * </ul>
       *
       * @return {@code true} if the state updater restores active tasks, {@code false} otherwise
       */
      // TODO: We would still return true if all active tasks to be restored
      //       are paused, in order to keep consistent behavior compared with
      //       state updater disabled. In the future we would modify this criterion
      //       with state updater always enabled to allow mixed processing / restoration.
      boolean restoresActiveTasks();
  
      /**
       * Gets standby tasks that are managed by the state updater.
       *
       * The state updater manages all standby tasks that were added with the {@link StateUpdater#add(Task)} and that have
       * not been removed from the state updater with one of the following methods:
       * <ul>
       *   <li>{@link StateUpdater#drainExceptionsAndFailedTasks()}</li>
       * </ul>
       *
       * @return set of all tasks managed by the state updater
       */
      Set<StandbyTask> standbyTasks();
  
      /**
       * Get the restore consumer instance id for telemetry, and complete the given future to return it.
       */
      KafkaFutureImpl<Uuid> restoreConsumerInstanceId(final Duration timeout);
  }
  