content: /*
   * Copyright 2014-2025 Real Logic Limited.
   *
   * 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
   *
   * https://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 io.aeron.cluster;
  
  /**
   * Timer service providing API to schedule timers in the Cluster.
   */
  public interface TimerService
  {
      /**
       * Called from the {@link #poll(long)}.
       */
      @FunctionalInterface
      interface TimerHandler
      {
          /**
           * Invoked for each expired timer.
           *
           * @param correlationId of the timer.
           * @return {@code true} if the timer event was processed or {@code false} otherwise, i.e. the timer should be
           * kept as non-expired.
           */
          boolean onTimerEvent(long correlationId);
      }
  
      /**
       * Called from the {@link #snapshot(TimerSnapshotTaker)}.
       */
      @FunctionalInterface
      interface TimerSnapshotTaker
      {
          /**
           * Take a snapshot of the timer.
           *
           * @param correlationId of the timer.
           * @param deadline      when the timer expires.
           */
          void snapshotTimer(long correlationId, long deadline);
      }
  
      /**
       * Max number of the timers to expire per single {@link #poll(long)}.
       */
      int POLL_LIMIT = 20;
  
      /**
       * Poll for expired timers. For each expired timer it invokes {@link TimerHandler#onTimerEvent(long)} on the
       * {@link TimerHandler} that was provided upon creation of this {@link TimerService} instance.
       * Poll can be terminated early if {@link #POLL_LIMIT} is reached or if {@link TimerHandler#onTimerEvent(long)}
       * returns {@code false}.
       *
       * @param now current time.
       * @return number of timers expired, never exceeds {@link #POLL_LIMIT}.
       */
      int poll(long now);
  
      /**
       * Schedule timer with the given {@code correlationId} and {@code deadline}.
       *
       * @param correlationId to associate with the timer.
       * @param deadline      when the timer expires.
       */
      void scheduleTimerForCorrelationId(long correlationId, long deadline);
  
      /**
       * Cancels timer by its {@code correlationId}.
       *
       * @param correlationId of the timer to cancel.
       * @return {@code true} if the timer was cancelled.
       */
      boolean cancelTimerByCorrelationId(long correlationId);
  
      /**
       * Takes a snapshot of the timer service state, i.e. serializes all non-expired timers.
       *
       * @param snapshotTaker to take a snapshot.
       */
      void snapshot(TimerSnapshotTaker snapshotTaker);
  
      /**
       * Set the current time from the Cluster in case the underlying implementation depends on it.
       *
       * @param now the current time.
       */
      void currentTime(long now);
  }
  