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.beam.runners.samza.runtime;
  
  import java.io.Serializable;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.List;
  import java.util.Queue;
  import java.util.ServiceLoader;
  import java.util.concurrent.CompletableFuture;
  import java.util.concurrent.CompletionStage;
  import java.util.concurrent.ConcurrentLinkedQueue;
  import java.util.stream.Collectors;
  import java.util.stream.StreamSupport;
  import org.apache.beam.runners.samza.SamzaPipelineExceptionContext;
  import org.apache.beam.runners.samza.SamzaPipelineOptions;
  import org.apache.beam.runners.samza.translation.TranslationContext;
  import org.apache.beam.runners.samza.util.FutureUtils;
  import org.apache.beam.runners.samza.util.SamzaPipelineExceptionListener;
  import org.apache.beam.sdk.util.UserCodeException;
  import org.apache.beam.sdk.values.WindowedValue;
  import org.apache.samza.config.Config;
  import org.apache.samza.context.Context;
  import org.apache.samza.operators.Scheduler;
  import org.apache.samza.operators.functions.AsyncFlatMapFunction;
  import org.apache.samza.operators.functions.ScheduledFunction;
  import org.apache.samza.operators.functions.WatermarkFunction;
  import org.joda.time.Instant;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Adaptor class that runs a Samza {@link Op} for BEAM in the Samza {@link AsyncFlatMapFunction}.
   * This class is initialized once for each Op within a Task for each Task.
   */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public class OpAdapter<InT, OutT, K>
      implements AsyncFlatMapFunction<OpMessage<InT>, OpMessage<OutT>>,
          WatermarkFunction<OpMessage<OutT>>,
          ScheduledFunction<KeyedTimerData<K>, OpMessage<OutT>>,
          Serializable {
    private static final Logger LOG = LoggerFactory.getLogger(OpAdapter.class);
  
    private final Op<InT, OutT, K> op;
    private final String transformFullName;
    private final transient SamzaPipelineOptions samzaPipelineOptions;
    private transient OpEmitter<OutT> emitter;
    private transient Config config;
    private transient Context context;
    private transient List<SamzaPipelineExceptionListener.Registrar> exceptionListeners;
  
    public static <InT, OutT, K> AsyncFlatMapFunction<OpMessage<InT>, OpMessage<OutT>> adapt(
        Op<InT, OutT, K> op, TranslationContext ctx) {
      return new OpAdapter<>(op, ctx.getTransformFullName(), ctx.getPipelineOptions());
    }
  
    private OpAdapter(
        Op<InT, OutT, K> op, String transformFullName, SamzaPipelineOptions samzaPipelineOptions) {
      this.op = op;
      this.transformFullName = transformFullName;
      this.samzaPipelineOptions = samzaPipelineOptions;
    }
  
    @Override
    public final void init(Context context) {
      this.emitter = new OpEmitterImpl<>();
      this.config = context.getJobContext().getConfig();
      this.context = context;
      this.exceptionListeners =
          StreamSupport.stream(
                  ServiceLoader.load(SamzaPipelineExceptionListener.Registrar.class).spliterator(),
                  false)
              .collect(Collectors.toList());
    }
  
    @Override
    public final void schedule(Scheduler<KeyedTimerData<K>> timerRegistry) {
      assert context != null;
  
      op.open(config, context, timerRegistry, emitter);
    }
  
    @Override
    public synchronized CompletionStage<Collection<OpMessage<OutT>>> apply(OpMessage<InT> message) {
      try {
        switch (message.getType()) {
          case ELEMENT:
            op.processElement(message.getElement(), emitter);
            break;
          case SIDE_INPUT:
            op.processSideInput(message.getViewId(), message.getViewElements(), emitter);
            break;
          case SIDE_INPUT_WATERMARK:
            op.processSideInputWatermark(message.getSideInputWatermark(), emitter);
            break;
          default:
            throw new IllegalArgumentException(
                String.format("Unexpected input type: %s", message.getType()));
        }
      } catch (Exception e) {
        LOG.error("Exception happened in transform: {}", transformFullName, e);
        notifyExceptionListeners(transformFullName, e, samzaPipelineOptions);
        throw UserCodeException.wrap(e);
      }
  
      CompletionStage<Collection<OpMessage<OutT>>> resultFuture =
          CompletableFuture.completedFuture(emitter.collectOutput());
  
      return FutureUtils.combineFutures(resultFuture, emitter.collectFuture());
    }
  
    @Override
    public synchronized Collection<OpMessage<OutT>> processWatermark(long time) {
      try {
        op.processWatermark(new Instant(time), emitter);
      } catch (Exception e) {
        LOG.error(
            "Op {} threw an exception during processing watermark", this.getClass().getName(), e);
        throw UserCodeException.wrap(e);
      }
  
      return emitter.collectOutput();
    }
  
    @Override
    public synchronized Long getOutputWatermark() {
      return emitter.collectWatermark();
    }
  
    @Override
    public synchronized Collection<OpMessage<OutT>> onCallback(
        KeyedTimerData<K> keyedTimerData, long time) {
      try {
        op.processTimer(keyedTimerData, emitter);
      } catch (Exception e) {
        LOG.error("Op {} threw an exception during processing timer", this.getClass().getName(), e);
        throw UserCodeException.wrap(e);
      }
  
      return emitter.collectOutput();
    }
  
    @Override
    public void close() {
      op.close();
    }
  
    static class OpEmitterImpl<OutT> implements OpEmitter<OutT> {
      private final Queue<OpMessage<OutT>> outputQueue;
      private CompletionStage<Collection<OpMessage<OutT>>> outputFuture;
      private Instant outputWatermark;
  
      OpEmitterImpl() {
        outputQueue = new ConcurrentLinkedQueue<>();
      }
  
      @Override
      public void emitElement(WindowedValue<OutT> element) {
        outputQueue.add(OpMessage.ofElement(element));
      }
  
      @Override
      public void emitFuture(CompletionStage<Collection<WindowedValue<OutT>>> resultFuture) {
        final CompletionStage<Collection<OpMessage<OutT>>> resultFutureWrapped =
            resultFuture.thenApply(
                res -> res.stream().map(OpMessage::ofElement).collect(Collectors.toList()));
  
        outputFuture = FutureUtils.combineFutures(outputFuture, resultFutureWrapped);
      }
  
      @Override
      public void emitWatermark(Instant watermark) {
        outputWatermark = watermark;
      }
  
      @Override
      public <T> void emitView(String id, WindowedValue<Iterable<T>> elements) {
        outputQueue.add(OpMessage.ofSideInput(id, elements));
      }
  
      @Override
      public Collection<OpMessage<OutT>> collectOutput() {
        final List<OpMessage<OutT>> outputList = new ArrayList<>();
        OpMessage<OutT> output;
        while ((output = outputQueue.poll()) != null) {
          outputList.add(output);
        }
        return outputList;
      }
  
      @Override
      public CompletionStage<Collection<OpMessage<OutT>>> collectFuture() {
        final CompletionStage<Collection<OpMessage<OutT>>> future = outputFuture;
        outputFuture = null;
        return future;
      }
  
      @Override
      public Long collectWatermark() {
        final Instant watermark = outputWatermark;
        outputWatermark = null;
        return watermark == null ? null : watermark.getMillis();
      }
    }
  
    private void notifyExceptionListeners(
        String transformFullName, Exception e, SamzaPipelineOptions samzaPipelineOptions) {
      try {
        exceptionListeners.forEach(
            listener -> {
              listener
                  .getExceptionListener(samzaPipelineOptions)
                  .onException(new SamzaPipelineExceptionContext(transformFullName, e));
            });
      } catch (Exception t) {
        // ignore exception/interruption by listeners
      }
    }
  }
  