/*
 * 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.nemo.runtime.executor;

import com.google.protobuf.ByteString;
import org.apache.nemo.runtime.common.RuntimeIdManager;
import org.apache.nemo.runtime.common.comm.ControlMessage;
import org.apache.nemo.runtime.common.message.MessageEnvironment;
import org.apache.nemo.runtime.common.message.PersistentConnectionToMasterMap;
import org.apache.reef.annotations.audience.EvaluatorSide;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.inject.Inject;
import java.util.concurrent.*;

/**
 * Metric sender that periodically flushes the collected metrics to Driver.
 */
@EvaluatorSide
public final class MetricManagerWorker implements MetricMessageSender {

  private final ScheduledExecutorService scheduledExecutorService;
  private final BlockingQueue<ControlMessage.Metric> metricMessageQueue;
  private final PersistentConnectionToMasterMap persistentConnectionToMasterMap;

  private static final int FLUSHING_PERIOD = 3000;
  private static final Logger LOG = LoggerFactory.getLogger(MetricManagerWorker.class.getName());

  @Inject
  private MetricManagerWorker(final PersistentConnectionToMasterMap persistentConnectionToMasterMap) {
    this.scheduledExecutorService = Executors.newSingleThreadScheduledExecutor();
    this.metricMessageQueue = new LinkedBlockingQueue<>();
    this.persistentConnectionToMasterMap = persistentConnectionToMasterMap;
    final Runnable batchMetricMessages = this::flushMetricMessageQueueToMaster;
    this.scheduledExecutorService.scheduleAtFixedRate(batchMetricMessages, 0,
      FLUSHING_PERIOD, TimeUnit.MILLISECONDS);
  }

  @Override
  public void flush() {
    flushMetricMessageQueueToMaster();
    persistentConnectionToMasterMap.getMessageSender(MessageEnvironment.RUNTIME_MASTER_MESSAGE_LISTENER_ID).send(
      ControlMessage.Message.newBuilder()
        .setId(RuntimeIdManager.generateMessageId())
        .setListenerId(MessageEnvironment.RUNTIME_MASTER_MESSAGE_LISTENER_ID)
        .setType(ControlMessage.MessageType.MetricFlushed)
        .build());
  }

  private synchronized void flushMetricMessageQueueToMaster() {
    if (!metricMessageQueue.isEmpty()) {
      // Build batched metric messages
      int size = metricMessageQueue.size();

      final ControlMessage.MetricMsg.Builder metricMsgBuilder = ControlMessage.MetricMsg.newBuilder();

      LOG.debug("MetricManagerWorker Size: {}", size);
      for (int i = 0; i < size; i++) {
        final ControlMessage.Metric metric = metricMessageQueue.poll();
        LOG.debug("MetricManagerWorker addMetric: {}, {}, {}", size, i, metric);
        metricMsgBuilder.addMetric(i, metric);
      }

      persistentConnectionToMasterMap.getMessageSender(MessageEnvironment.RUNTIME_MASTER_MESSAGE_LISTENER_ID).send(
        ControlMessage.Message.newBuilder()
          .setId(RuntimeIdManager.generateMessageId())
          .setListenerId(MessageEnvironment.RUNTIME_MASTER_MESSAGE_LISTENER_ID)
          .setType(ControlMessage.MessageType.MetricMessageReceived)
          .setMetricMsg(metricMsgBuilder.build())
          .build());
    }
  }

  @Override
  public void send(final String metricType, final String metricId,
                   final String metricField, final byte[] metricValue) {
    metricMessageQueue.add(
      ControlMessage.Metric.newBuilder()
        .setMetricType(metricType)
        .setMetricId(metricId)
        .setMetricField(metricField)
        .setMetricValue(ByteString.copyFrom(metricValue))
        .build());
  }

  @Override
  public void close() {
    scheduledExecutorService.shutdownNow();
    flushMetricMessageQueueToMaster();
  }
}