/*
 * 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.fnexecution.control;

import static org.apache.beam.vendor.guava.v20_0.com.google.common.base.Preconditions.checkState;
import static org.hamcrest.Matchers.allOf;
import static org.hamcrest.Matchers.containsInAnyOrder;
import static org.hamcrest.Matchers.equalTo;
import static org.junit.Assert.assertThat;
import static org.junit.Assert.assertTrue;
import static org.junit.Assert.fail;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.ThreadFactory;
import java.util.function.Function;
import org.apache.beam.fn.harness.FnHarness;
import org.apache.beam.model.fnexecution.v1.BeamFnApi.ProcessBundleProgressResponse;
import org.apache.beam.model.fnexecution.v1.BeamFnApi.ProcessBundleResponse;
import org.apache.beam.model.fnexecution.v1.BeamFnApi.Target;
import org.apache.beam.model.pipeline.v1.MetricsApi.MonitoringInfo;
import org.apache.beam.model.pipeline.v1.RunnerApi;
import org.apache.beam.runners.core.construction.PipelineTranslation;
import org.apache.beam.runners.core.construction.graph.ExecutableStage;
import org.apache.beam.runners.core.construction.graph.FusedPipeline;
import org.apache.beam.runners.core.construction.graph.GreedyPipelineFuser;
import org.apache.beam.runners.core.metrics.DistributionData;
import org.apache.beam.runners.core.metrics.MonitoringInfoConstants;
import org.apache.beam.runners.core.metrics.MonitoringInfoConstants.Urns;
import org.apache.beam.runners.core.metrics.MonitoringInfoMatchers;
import org.apache.beam.runners.core.metrics.SimpleMonitoringInfoBuilder;
import org.apache.beam.runners.fnexecution.GrpcContextHeaderAccessorProvider;
import org.apache.beam.runners.fnexecution.GrpcFnServer;
import org.apache.beam.runners.fnexecution.InProcessServerFactory;
import org.apache.beam.runners.fnexecution.control.ProcessBundleDescriptors.ExecutableProcessBundleDescriptor;
import org.apache.beam.runners.fnexecution.control.SdkHarnessClient.ActiveBundle;
import org.apache.beam.runners.fnexecution.control.SdkHarnessClient.BundleProcessor;
import org.apache.beam.runners.fnexecution.data.GrpcDataService;
import org.apache.beam.runners.fnexecution.logging.GrpcLoggingService;
import org.apache.beam.runners.fnexecution.logging.Slf4jLogWriter;
import org.apache.beam.runners.fnexecution.state.GrpcStateService;
import org.apache.beam.runners.fnexecution.state.StateRequestHandler;
import org.apache.beam.runners.fnexecution.state.StateRequestHandlers;
import org.apache.beam.runners.fnexecution.state.StateRequestHandlers.BagUserStateHandler;
import org.apache.beam.runners.fnexecution.state.StateRequestHandlers.BagUserStateHandlerFactory;
import org.apache.beam.runners.fnexecution.state.StateRequestHandlers.SideInputHandler;
import org.apache.beam.runners.fnexecution.state.StateRequestHandlers.SideInputHandlerFactory;
import org.apache.beam.sdk.Pipeline;
import org.apache.beam.sdk.coders.BigEndianLongCoder;
import org.apache.beam.sdk.coders.ByteArrayCoder;
import org.apache.beam.sdk.coders.Coder;
import org.apache.beam.sdk.coders.CoderException;
import org.apache.beam.sdk.coders.KvCoder;
import org.apache.beam.sdk.coders.StringUtf8Coder;
import org.apache.beam.sdk.coders.VoidCoder;
import org.apache.beam.sdk.fn.data.FnDataReceiver;
import org.apache.beam.sdk.fn.stream.OutboundObserverFactory;
import org.apache.beam.sdk.fn.test.InProcessManagedChannelFactory;
import org.apache.beam.sdk.metrics.Counter;
import org.apache.beam.sdk.metrics.Metrics;
import org.apache.beam.sdk.options.PipelineOptionsFactory;
import org.apache.beam.sdk.state.BagState;
import org.apache.beam.sdk.state.ReadableState;
import org.apache.beam.sdk.state.StateSpec;
import org.apache.beam.sdk.state.StateSpecs;
import org.apache.beam.sdk.state.TimeDomain;
import org.apache.beam.sdk.state.Timer;
import org.apache.beam.sdk.state.TimerSpec;
import org.apache.beam.sdk.state.TimerSpecs;
import org.apache.beam.sdk.testing.ResetDateTimeProvider;
import org.apache.beam.sdk.transforms.DoFn;
import org.apache.beam.sdk.transforms.Flatten;
import org.apache.beam.sdk.transforms.GroupByKey;
import org.apache.beam.sdk.transforms.Impulse;
import org.apache.beam.sdk.transforms.ParDo;
import org.apache.beam.sdk.transforms.ParDo.SingleOutput;
import org.apache.beam.sdk.transforms.View;
import org.apache.beam.sdk.transforms.WithKeys;
import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
import org.apache.beam.sdk.transforms.windowing.GlobalWindow;
import org.apache.beam.sdk.util.CoderUtils;
import org.apache.beam.sdk.util.WindowedValue;
import org.apache.beam.sdk.values.KV;
import org.apache.beam.sdk.values.PCollection;
import org.apache.beam.sdk.values.PCollectionList;
import org.apache.beam.sdk.values.PCollectionView;
import org.apache.beam.vendor.grpc.v1p13p1.com.google.protobuf.ByteString;
import org.apache.beam.vendor.guava.v20_0.com.google.common.base.Optional;
import org.apache.beam.vendor.guava.v20_0.com.google.common.collect.Collections2;
import org.apache.beam.vendor.guava.v20_0.com.google.common.collect.ImmutableMap;
import org.apache.beam.vendor.guava.v20_0.com.google.common.collect.ImmutableSet;
import org.apache.beam.vendor.guava.v20_0.com.google.common.collect.Iterables;
import org.apache.beam.vendor.guava.v20_0.com.google.common.collect.Iterators;
import org.apache.beam.vendor.guava.v20_0.com.google.common.collect.Sets;
import org.apache.beam.vendor.guava.v20_0.com.google.common.util.concurrent.ThreadFactoryBuilder;
import org.hamcrest.Matcher;
import org.hamcrest.Matchers;
import org.hamcrest.collection.IsEmptyIterable;
import org.hamcrest.collection.IsIterableContainingInOrder;
import org.joda.time.DateTimeUtils;
import org.joda.time.Duration;
import org.junit.After;
import org.junit.Before;
import org.junit.Rule;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Tests the execution of a pipeline from specification time to executing a single fused stage,
 * going through pipeline fusion.
 */
@RunWith(JUnit4.class)
public class RemoteExecutionTest implements Serializable {
  @Rule public transient ResetDateTimeProvider resetDateTimeProvider = new ResetDateTimeProvider();

  private static final Logger LOG = LoggerFactory.getLogger(RemoteExecutionTest.class);

  private transient GrpcFnServer<FnApiControlClientPoolService> controlServer;
  private transient GrpcFnServer<GrpcDataService> dataServer;
  private transient GrpcFnServer<GrpcStateService> stateServer;
  private transient GrpcFnServer<GrpcLoggingService> loggingServer;
  private transient GrpcStateService stateDelegator;
  private transient SdkHarnessClient controlClient;

  private transient ExecutorService serverExecutor;
  private transient ExecutorService sdkHarnessExecutor;
  private transient Future<?> sdkHarnessExecutorFuture;

  @Before
  public void setup() throws Exception {
    // Setup execution-time servers
    ThreadFactory threadFactory = new ThreadFactoryBuilder().setDaemon(true).build();
    serverExecutor = Executors.newCachedThreadPool(threadFactory);
    InProcessServerFactory serverFactory = InProcessServerFactory.create();
    dataServer =
        GrpcFnServer.allocatePortAndCreateFor(
            GrpcDataService.create(serverExecutor, OutboundObserverFactory.serverDirect()),
            serverFactory);
    loggingServer =
        GrpcFnServer.allocatePortAndCreateFor(
            GrpcLoggingService.forWriter(Slf4jLogWriter.getDefault()), serverFactory);
    stateDelegator = GrpcStateService.create();
    stateServer = GrpcFnServer.allocatePortAndCreateFor(stateDelegator, serverFactory);

    ControlClientPool clientPool = MapControlClientPool.create();
    controlServer =
        GrpcFnServer.allocatePortAndCreateFor(
            FnApiControlClientPoolService.offeringClientsToPool(
                clientPool.getSink(), GrpcContextHeaderAccessorProvider.getHeaderAccessor()),
            serverFactory);

    // Create the SDK harness, and wait until it connects
    sdkHarnessExecutor = Executors.newSingleThreadExecutor(threadFactory);
    sdkHarnessExecutorFuture =
        sdkHarnessExecutor.submit(
            () -> {
              try {
                FnHarness.main(
                    "id",
                    PipelineOptionsFactory.create(),
                    loggingServer.getApiServiceDescriptor(),
                    controlServer.getApiServiceDescriptor(),
                    InProcessManagedChannelFactory.create(),
                    OutboundObserverFactory.clientDirect());
              } catch (Exception e) {
                throw new RuntimeException(e);
              }
            });
    // TODO: https://issues.apache.org/jira/browse/BEAM-4149 Use proper worker id.
    InstructionRequestHandler controlClient =
        clientPool.getSource().take("", java.time.Duration.ofSeconds(2));
    this.controlClient = SdkHarnessClient.usingFnApiClient(controlClient, dataServer.getService());
  }

  @After
  public void tearDown() throws Exception {
    controlServer.close();
    stateServer.close();
    dataServer.close();
    loggingServer.close();
    controlClient.close();
    sdkHarnessExecutor.shutdownNow();
    serverExecutor.shutdownNow();
    try {
      sdkHarnessExecutorFuture.get();
    } catch (ExecutionException e) {
      if (e.getCause() instanceof RuntimeException
          && e.getCause().getCause() instanceof InterruptedException) {
        // expected
      } else {
        throw e;
      }
    }
  }

  @Test
  public void testExecution() throws Exception {
    Pipeline p = Pipeline.create();
    p.apply("impulse", Impulse.create())
        .apply(
            "create",
            ParDo.of(
                new DoFn<byte[], String>() {
                  @ProcessElement
                  public void process(ProcessContext ctxt) {
                    ctxt.output("zero");
                    ctxt.output("one");
                    ctxt.output("two");
                  }
                }))
        .apply(
            "len",
            ParDo.of(
                new DoFn<String, Long>() {
                  @ProcessElement
                  public void process(ProcessContext ctxt) {
                    ctxt.output((long) ctxt.element().length());
                  }
                }))
        .apply("addKeys", WithKeys.of("foo"))
        // Use some unknown coders
        .setCoder(KvCoder.of(StringUtf8Coder.of(), BigEndianLongCoder.of()))
        // Force the output to be materialized
        .apply("gbk", GroupByKey.create());

    RunnerApi.Pipeline pipelineProto = PipelineTranslation.toProto(p);
    FusedPipeline fused = GreedyPipelineFuser.fuse(pipelineProto);
    checkState(fused.getFusedStages().size() == 1, "Expected exactly one fused stage");
    ExecutableStage stage = fused.getFusedStages().iterator().next();

    ExecutableProcessBundleDescriptor descriptor =
        ProcessBundleDescriptors.fromExecutableStage(
            "my_stage", stage, dataServer.getApiServiceDescriptor());

    BundleProcessor processor =
        controlClient.getProcessor(
            descriptor.getProcessBundleDescriptor(), descriptor.getRemoteInputDestinations());
    Map<Target, ? super Coder<WindowedValue<?>>> outputTargets = descriptor.getOutputTargetCoders();
    Map<Target, Collection<? super WindowedValue<?>>> outputValues = new HashMap<>();
    Map<Target, RemoteOutputReceiver<?>> outputReceivers = new HashMap<>();
    for (Entry<Target, ? super Coder<WindowedValue<?>>> targetCoder : outputTargets.entrySet()) {
      List<? super WindowedValue<?>> outputContents =
          Collections.synchronizedList(new ArrayList<>());
      outputValues.put(targetCoder.getKey(), outputContents);
      outputReceivers.put(
          targetCoder.getKey(),
          RemoteOutputReceiver.of(
              (Coder) targetCoder.getValue(),
              (FnDataReceiver<? super WindowedValue<?>>) outputContents::add));
    }
    // The impulse example

    try (ActiveBundle bundle =
        processor.newBundle(outputReceivers, BundleProgressHandler.ignored())) {
      Iterables.getOnlyElement(bundle.getInputReceivers().values())
          .accept(WindowedValue.valueInGlobalWindow(new byte[0]));
    }

    for (Collection<? super WindowedValue<?>> windowedValues : outputValues.values()) {
      assertThat(
          windowedValues,
          containsInAnyOrder(
              WindowedValue.valueInGlobalWindow(byteValueOf("foo", 4)),
              WindowedValue.valueInGlobalWindow(byteValueOf("foo", 3)),
              WindowedValue.valueInGlobalWindow(byteValueOf("foo", 3))));
    }
  }

  @Test
  public void testBundleProcessorThrowsExecutionExceptionWhenUserCodeThrows() throws Exception {
    Pipeline p = Pipeline.create();
    p.apply("impulse", Impulse.create())
        .apply(
            "create",
            ParDo.of(
                new DoFn<byte[], KV<String, String>>() {
                  @ProcessElement
                  public void process(ProcessContext ctxt) throws Exception {
                    String element =
                        CoderUtils.decodeFromByteArray(StringUtf8Coder.of(), ctxt.element());
                    if (element.equals("X")) {
                      throw new Exception("testBundleExecutionFailure");
                    }
                    ctxt.output(KV.of(element, element));
                  }
                }))
        .apply("gbk", GroupByKey.create());

    RunnerApi.Pipeline pipelineProto = PipelineTranslation.toProto(p);
    FusedPipeline fused = GreedyPipelineFuser.fuse(pipelineProto);
    checkState(fused.getFusedStages().size() == 1, "Expected exactly one fused stage");
    ExecutableStage stage = fused.getFusedStages().iterator().next();

    ExecutableProcessBundleDescriptor descriptor =
        ProcessBundleDescriptors.fromExecutableStage(
            "my_stage", stage, dataServer.getApiServiceDescriptor());

    BundleProcessor processor =
        controlClient.getProcessor(
            descriptor.getProcessBundleDescriptor(), descriptor.getRemoteInputDestinations());
    Map<Target, ? super Coder<WindowedValue<?>>> outputTargets = descriptor.getOutputTargetCoders();
    Map<Target, Collection<? super WindowedValue<?>>> outputValues = new HashMap<>();
    Map<Target, RemoteOutputReceiver<?>> outputReceivers = new HashMap<>();
    for (Entry<Target, ? super Coder<WindowedValue<?>>> targetCoder : outputTargets.entrySet()) {
      List<? super WindowedValue<?>> outputContents =
          Collections.synchronizedList(new ArrayList<>());
      outputValues.put(targetCoder.getKey(), outputContents);
      outputReceivers.put(
          targetCoder.getKey(),
          RemoteOutputReceiver.of(
              (Coder) targetCoder.getValue(),
              (FnDataReceiver<? super WindowedValue<?>>) outputContents::add));
    }

    try (ActiveBundle bundle =
        processor.newBundle(outputReceivers, BundleProgressHandler.ignored())) {
      Iterables.getOnlyElement(bundle.getInputReceivers().values())
          .accept(
              WindowedValue.valueInGlobalWindow(
                  CoderUtils.encodeToByteArray(StringUtf8Coder.of(), "Y")));
    }

    try {
      try (ActiveBundle bundle =
          processor.newBundle(outputReceivers, BundleProgressHandler.ignored())) {
        Iterables.getOnlyElement(bundle.getInputReceivers().values())
            .accept(
                WindowedValue.valueInGlobalWindow(
                    CoderUtils.encodeToByteArray(StringUtf8Coder.of(), "X")));
      }
      // Fail the test if we reach this point and never threw the exception.
      fail();
    } catch (ExecutionException e) {
      assertTrue(e.getMessage().contains("testBundleExecutionFailure"));
    }

    try (ActiveBundle bundle =
        processor.newBundle(outputReceivers, BundleProgressHandler.ignored())) {
      Iterables.getOnlyElement(bundle.getInputReceivers().values())
          .accept(
              WindowedValue.valueInGlobalWindow(
                  CoderUtils.encodeToByteArray(StringUtf8Coder.of(), "Z")));
    }

    for (Collection<? super WindowedValue<?>> windowedValues : outputValues.values()) {
      assertThat(
          windowedValues,
          containsInAnyOrder(
              WindowedValue.valueInGlobalWindow(KV.of("Y", "Y")),
              WindowedValue.valueInGlobalWindow(KV.of("Z", "Z"))));
    }
  }

  @Test
  public void testExecutionWithSideInput() throws Exception {
    Pipeline p = Pipeline.create();
    PCollection<String> input =
        p.apply("impulse", Impulse.create())
            .apply(
                "create",
                ParDo.of(
                    new DoFn<byte[], String>() {
                      @ProcessElement
                      public void process(ProcessContext ctxt) {
                        ctxt.output("zero");
                        ctxt.output("one");
                        ctxt.output("two");
                      }
                    }))
            .setCoder(StringUtf8Coder.of());
    PCollectionView<Iterable<String>> view = input.apply("createSideInput", View.asIterable());

    input
        .apply(
            "readSideInput",
            ParDo.of(
                    new DoFn<String, KV<String, String>>() {
                      @ProcessElement
                      public void processElement(ProcessContext context) {
                        for (String value : context.sideInput(view)) {
                          context.output(KV.of(context.element(), value));
                        }
                      }
                    })
                .withSideInputs(view))
        .setCoder(KvCoder.of(StringUtf8Coder.of(), StringUtf8Coder.of()))
        // Force the output to be materialized
        .apply("gbk", GroupByKey.create());

    RunnerApi.Pipeline pipelineProto = PipelineTranslation.toProto(p);
    FusedPipeline fused = GreedyPipelineFuser.fuse(pipelineProto);
    Optional<ExecutableStage> optionalStage =
        Iterables.tryFind(
            fused.getFusedStages(), (ExecutableStage stage) -> !stage.getSideInputs().isEmpty());
    checkState(optionalStage.isPresent(), "Expected a stage with side inputs.");
    ExecutableStage stage = optionalStage.get();

    ExecutableProcessBundleDescriptor descriptor =
        ProcessBundleDescriptors.fromExecutableStage(
            "test_stage",
            stage,
            dataServer.getApiServiceDescriptor(),
            stateServer.getApiServiceDescriptor());

    BundleProcessor processor =
        controlClient.getProcessor(
            descriptor.getProcessBundleDescriptor(),
            descriptor.getRemoteInputDestinations(),
            stateDelegator);
    Map<Target, Coder<WindowedValue<?>>> outputTargets = descriptor.getOutputTargetCoders();
    Map<Target, Collection<WindowedValue<?>>> outputValues = new HashMap<>();
    Map<Target, RemoteOutputReceiver<?>> outputReceivers = new HashMap<>();
    for (Entry<Target, Coder<WindowedValue<?>>> targetCoder : outputTargets.entrySet()) {
      List<WindowedValue<?>> outputContents = Collections.synchronizedList(new ArrayList<>());
      outputValues.put(targetCoder.getKey(), outputContents);
      outputReceivers.put(
          targetCoder.getKey(),
          RemoteOutputReceiver.of(targetCoder.getValue(), outputContents::add));
    }

    Iterable<String> sideInputData = Arrays.asList("A", "B", "C");
    StateRequestHandler stateRequestHandler =
        StateRequestHandlers.forSideInputHandlerFactory(
            descriptor.getSideInputSpecs(),
            new SideInputHandlerFactory() {
              @Override
              public <T, V, W extends BoundedWindow> SideInputHandler<V, W> forSideInput(
                  String pTransformId,
                  String sideInputId,
                  RunnerApi.FunctionSpec accessPattern,
                  Coder<T> elementCoder,
                  Coder<W> windowCoder) {
                return new SideInputHandler<V, W>() {
                  @Override
                  public Iterable<V> get(byte[] key, W window) {
                    return (Iterable) sideInputData;
                  }

                  @Override
                  public Coder<V> resultCoder() {
                    return ((KvCoder) elementCoder).getValueCoder();
                  }
                };
              }
            });
    BundleProgressHandler progressHandler = BundleProgressHandler.ignored();

    try (ActiveBundle bundle =
        processor.newBundle(outputReceivers, stateRequestHandler, progressHandler)) {
      Iterables.getOnlyElement(bundle.getInputReceivers().values())
          .accept(WindowedValue.valueInGlobalWindow("X"));
      Iterables.getOnlyElement(bundle.getInputReceivers().values())
          .accept(WindowedValue.valueInGlobalWindow("Y"));
    }
    for (Collection<WindowedValue<?>> windowedValues : outputValues.values()) {
      assertThat(
          windowedValues,
          containsInAnyOrder(
              WindowedValue.valueInGlobalWindow(KV.of("X", "A")),
              WindowedValue.valueInGlobalWindow(KV.of("X", "B")),
              WindowedValue.valueInGlobalWindow(KV.of("X", "C")),
              WindowedValue.valueInGlobalWindow(KV.of("Y", "A")),
              WindowedValue.valueInGlobalWindow(KV.of("Y", "B")),
              WindowedValue.valueInGlobalWindow(KV.of("Y", "C"))));
    }
  }

  @Test
  public void testMetrics() throws Exception {
    final String processUserCounterName = "processUserCounter";
    final String startUserCounterName = "startUserCounter";
    final String finishUserCounterName = "finishUserCounter";
    final String processUserDistributionName = "processUserDistribution";
    final String startUserDistributionName = "startUserDistribution";
    final String finishUserDistributionName = "finishUserDistribution";
    Pipeline p = Pipeline.create();
    // TODO(BEAM-6597): Remove sleeps in this test after collecting MonitoringInfos in
    // ProcessBundleProgressResponses. Use CountDownLatches to wait in start, finish and process
    // functions and open the latches when valid metrics are seen in the progress responses.
    PCollection<String> input =
        p.apply("impulse", Impulse.create())
            .apply(
                "create",
                ParDo.of(
                    new DoFn<byte[], String>() {
                      private boolean emitted = false;
                      private Counter startCounter =
                          Metrics.counter(RemoteExecutionTest.class, startUserCounterName);

                      @StartBundle
                      public void startBundle() throws InterruptedException {
                        Thread.sleep(1000);
                        startCounter.inc(10);
                        Metrics.distribution(RemoteExecutionTest.class, startUserDistributionName)
                            .update(10);
                      }

                      @SuppressWarnings("unused")
                      @ProcessElement
                      public void processElement(ProcessContext ctxt) throws InterruptedException {
                        // TODO(BEAM-6467): Impulse is producing two elements instead of one.
                        // So add this check to only emit these three elemenets.
                        if (!emitted) {
                          ctxt.output("zero");
                          ctxt.output("one");
                          ctxt.output("two");
                          Thread.sleep(1000);
                          Metrics.counter(RemoteExecutionTest.class, processUserCounterName).inc();
                          Metrics.distribution(
                                  RemoteExecutionTest.class, processUserDistributionName)
                              .update(1);
                        }
                        emitted = true;
                      }

                      @DoFn.FinishBundle
                      public void finishBundle() throws InterruptedException {
                        Thread.sleep(1000);
                        Metrics.counter(RemoteExecutionTest.class, finishUserCounterName).inc(100);
                        Metrics.distribution(RemoteExecutionTest.class, finishUserDistributionName)
                            .update(100);
                      }
                    }))
            .setCoder(StringUtf8Coder.of());

    SingleOutput<String, String> pardo =
        ParDo.of(
            new DoFn<String, String>() {
              @ProcessElement
              public void process(ProcessContext ctxt) {
                // Output the element twice to keep unique numbers in asserts, 6 output elements.
                ctxt.output(ctxt.element());
                ctxt.output(ctxt.element());
              }
            });
    input.apply("processA", pardo).setCoder(StringUtf8Coder.of());
    input.apply("processB", pardo).setCoder(StringUtf8Coder.of());

    RunnerApi.Pipeline pipelineProto = PipelineTranslation.toProto(p);
    FusedPipeline fused = GreedyPipelineFuser.fuse(pipelineProto);
    Optional<ExecutableStage> optionalStage =
        Iterables.tryFind(fused.getFusedStages(), (ExecutableStage stage) -> true);
    checkState(optionalStage.isPresent(), "Expected a stage with side inputs.");
    ExecutableStage stage = optionalStage.get();

    ExecutableProcessBundleDescriptor descriptor =
        ProcessBundleDescriptors.fromExecutableStage(
            "test_stage",
            stage,
            dataServer.getApiServiceDescriptor(),
            stateServer.getApiServiceDescriptor());

    BundleProcessor processor =
        controlClient.getProcessor(
            descriptor.getProcessBundleDescriptor(),
            descriptor.getRemoteInputDestinations(),
            stateDelegator);

    Map<Target, Coder<WindowedValue<?>>> outputTargets = descriptor.getOutputTargetCoders();
    Map<Target, Collection<WindowedValue<?>>> outputValues = new HashMap<>();
    Map<Target, RemoteOutputReceiver<?>> outputReceivers = new HashMap<>();
    for (Entry<Target, Coder<WindowedValue<?>>> targetCoder : outputTargets.entrySet()) {
      List<WindowedValue<?>> outputContents = Collections.synchronizedList(new ArrayList<>());
      outputValues.put(targetCoder.getKey(), outputContents);
      outputReceivers.put(
          targetCoder.getKey(),
          RemoteOutputReceiver.of(targetCoder.getValue(), outputContents::add));
    }

    Iterable<String> sideInputData = Arrays.asList("A", "B", "C");

    StateRequestHandler stateRequestHandler =
        StateRequestHandlers.forSideInputHandlerFactory(
            descriptor.getSideInputSpecs(),
            new SideInputHandlerFactory() {
              @Override
              public <T, V, W extends BoundedWindow> SideInputHandler<V, W> forSideInput(
                  String pTransformId,
                  String sideInputId,
                  RunnerApi.FunctionSpec accessPattern,
                  Coder<T> elementCoder,
                  Coder<W> windowCoder) {
                return new SideInputHandler<V, W>() {
                  @Override
                  public Iterable<V> get(byte[] key, W window) {
                    return (Iterable) sideInputData;
                  }

                  @Override
                  public Coder<V> resultCoder() {
                    return ((KvCoder) elementCoder).getValueCoder();
                  }
                };
              }
            });

    String testPTransformId = "create/ParMultiDo(Anonymous)";
    BundleProgressHandler progressHandler =
        new BundleProgressHandler() {
          @Override
          public void onProgress(ProcessBundleProgressResponse progress) {}

          @Override
          public void onCompleted(ProcessBundleResponse response) {
            List<Matcher<MonitoringInfo>> matchers = new ArrayList<Matcher<MonitoringInfo>>();

            // User Counters.
            SimpleMonitoringInfoBuilder builder = new SimpleMonitoringInfoBuilder();
            builder
                .setUrn(MonitoringInfoConstants.Urns.USER_COUNTER)
                .setLabel(
                    MonitoringInfoConstants.Labels.NAMESPACE, RemoteExecutionTest.class.getName())
                .setLabel(MonitoringInfoConstants.Labels.NAME, processUserCounterName);
            builder.setLabel(
                MonitoringInfoConstants.Labels.PTRANSFORM, "create/ParMultiDo(Anonymous)");
            builder.setInt64Value(1);
            matchers.add(MonitoringInfoMatchers.matchSetFields(builder.build()));

            builder = new SimpleMonitoringInfoBuilder();
            builder
                .setUrn(MonitoringInfoConstants.Urns.USER_COUNTER)
                .setLabel(
                    MonitoringInfoConstants.Labels.NAMESPACE, RemoteExecutionTest.class.getName())
                .setLabel(MonitoringInfoConstants.Labels.NAME, startUserCounterName);
            builder.setLabel(
                MonitoringInfoConstants.Labels.PTRANSFORM, "create/ParMultiDo(Anonymous)");
            builder.setInt64Value(10);
            matchers.add(MonitoringInfoMatchers.matchSetFields(builder.build()));

            builder = new SimpleMonitoringInfoBuilder();
            builder
                .setUrn(MonitoringInfoConstants.Urns.USER_COUNTER)
                .setLabel(
                    MonitoringInfoConstants.Labels.NAMESPACE, RemoteExecutionTest.class.getName())
                .setLabel(MonitoringInfoConstants.Labels.NAME, finishUserCounterName);
            builder.setLabel(
                MonitoringInfoConstants.Labels.PTRANSFORM, "create/ParMultiDo(Anonymous)");
            builder.setInt64Value(100);
            matchers.add(MonitoringInfoMatchers.matchSetFields(builder.build()));

            // User Distributions.
            builder
                .setUrn(MonitoringInfoConstants.Urns.USER_DISTRIBUTION_COUNTER)
                .setLabel(
                    MonitoringInfoConstants.Labels.NAMESPACE, RemoteExecutionTest.class.getName())
                .setLabel(MonitoringInfoConstants.Labels.NAME, processUserDistributionName);
            builder.setLabel(
                MonitoringInfoConstants.Labels.PTRANSFORM, "create/ParMultiDo(Anonymous)");
            builder.setInt64DistributionValue(DistributionData.create(1, 1, 1, 1));
            matchers.add(MonitoringInfoMatchers.matchSetFields(builder.build()));

            builder = new SimpleMonitoringInfoBuilder();
            builder
                .setUrn(MonitoringInfoConstants.Urns.USER_DISTRIBUTION_COUNTER)
                .setLabel(
                    MonitoringInfoConstants.Labels.NAMESPACE, RemoteExecutionTest.class.getName())
                .setLabel(MonitoringInfoConstants.Labels.NAME, startUserDistributionName);
            builder.setLabel(
                MonitoringInfoConstants.Labels.PTRANSFORM, "create/ParMultiDo(Anonymous)");
            builder.setInt64DistributionValue(DistributionData.create(10, 1, 10, 10));
            matchers.add(MonitoringInfoMatchers.matchSetFields(builder.build()));

            builder = new SimpleMonitoringInfoBuilder();
            builder
                .setUrn(MonitoringInfoConstants.Urns.USER_DISTRIBUTION_COUNTER)
                .setLabel(
                    MonitoringInfoConstants.Labels.NAMESPACE, RemoteExecutionTest.class.getName())
                .setLabel(MonitoringInfoConstants.Labels.NAME, finishUserDistributionName);
            builder.setLabel(
                MonitoringInfoConstants.Labels.PTRANSFORM, "create/ParMultiDo(Anonymous)");
            builder.setInt64DistributionValue(DistributionData.create(100, 1, 100, 100));
            matchers.add(MonitoringInfoMatchers.matchSetFields(builder.build()));

            // The element counter should be counted only once for the pcollection.
            // So there should be only two elements.
            builder = new SimpleMonitoringInfoBuilder();
            builder.setUrn(MonitoringInfoConstants.Urns.ELEMENT_COUNT);
            builder.setLabel(MonitoringInfoConstants.Labels.PCOLLECTION, "impulse.out");
            builder.setInt64Value(2);
            matchers.add(MonitoringInfoMatchers.matchSetFields(builder.build()));

            builder = new SimpleMonitoringInfoBuilder();
            builder.setUrn(MonitoringInfoConstants.Urns.ELEMENT_COUNT);
            builder.setLabel(
                MonitoringInfoConstants.Labels.PCOLLECTION, "create/ParMultiDo(Anonymous).output");
            builder.setInt64Value(3);
            matchers.add(MonitoringInfoMatchers.matchSetFields(builder.build()));

            // Verify that the element count is not double counted if two PCollections consume it.
            builder = new SimpleMonitoringInfoBuilder();
            builder.setUrn(MonitoringInfoConstants.Urns.ELEMENT_COUNT);
            builder.setLabel(
                MonitoringInfoConstants.Labels.PCOLLECTION,
                "processA/ParMultiDo(Anonymous).output");
            builder.setInt64Value(6);
            matchers.add(MonitoringInfoMatchers.matchSetFields(builder.build()));

            builder = new SimpleMonitoringInfoBuilder();
            builder.setUrn(MonitoringInfoConstants.Urns.ELEMENT_COUNT);
            builder.setLabel(
                MonitoringInfoConstants.Labels.PCOLLECTION,
                "processB/ParMultiDo(Anonymous).output");
            builder.setInt64Value(6);
            matchers.add(MonitoringInfoMatchers.matchSetFields(builder.build()));

            // Check for execution time metrics for the testPTransformId
            builder = new SimpleMonitoringInfoBuilder();
            builder.setUrn(MonitoringInfoConstants.Urns.START_BUNDLE_MSECS);
            builder.setInt64TypeUrn();
            builder.setLabel(MonitoringInfoConstants.Labels.PTRANSFORM, testPTransformId);
            matchers.add(
                allOf(
                    MonitoringInfoMatchers.matchSetFields(builder.build()),
                    MonitoringInfoMatchers.valueGreaterThan(0)));

            // Check for execution time metrics for the testPTransformId
            builder = new SimpleMonitoringInfoBuilder();
            builder.setUrn(Urns.PROCESS_BUNDLE_MSECS);
            builder.setInt64TypeUrn();
            builder.setLabel(MonitoringInfoConstants.Labels.PTRANSFORM, testPTransformId);
            matchers.add(
                allOf(
                    MonitoringInfoMatchers.matchSetFields(builder.build()),
                    MonitoringInfoMatchers.valueGreaterThan(0)));

            builder = new SimpleMonitoringInfoBuilder();
            builder.setUrn(Urns.FINISH_BUNDLE_MSECS);
            builder.setInt64TypeUrn();
            builder.setLabel(MonitoringInfoConstants.Labels.PTRANSFORM, testPTransformId);
            matchers.add(
                allOf(
                    MonitoringInfoMatchers.matchSetFields(builder.build()),
                    MonitoringInfoMatchers.valueGreaterThan(0)));

            for (Matcher<MonitoringInfo> matcher : matchers) {
              assertThat(response.getMonitoringInfosList(), Matchers.hasItem(matcher));
            }
          }
        };

    try (ActiveBundle bundle =
        processor.newBundle(outputReceivers, stateRequestHandler, progressHandler)) {
      Iterables.getOnlyElement(bundle.getInputReceivers().values())
          .accept(
              WindowedValue.valueInGlobalWindow(
                  CoderUtils.encodeToByteArray(StringUtf8Coder.of(), "X")));
      Iterables.getOnlyElement(bundle.getInputReceivers().values())
          .accept(
              WindowedValue.valueInGlobalWindow(
                  CoderUtils.encodeToByteArray(StringUtf8Coder.of(), "Y")));
    }
  }

  @Test
  public void testExecutionWithUserState() throws Exception {
    Pipeline p = Pipeline.create();
    final String stateId = "foo";
    final String stateId2 = "foo2";

    p.apply("impulse", Impulse.create())
        .apply(
            "create",
            ParDo.of(
                new DoFn<byte[], KV<String, String>>() {
                  @ProcessElement
                  public void process(ProcessContext ctxt) {}
                }))
        .setCoder(KvCoder.of(StringUtf8Coder.of(), StringUtf8Coder.of()))
        .apply(
            "userState",
            ParDo.of(
                new DoFn<KV<String, String>, KV<String, String>>() {

                  @StateId(stateId)
                  private final StateSpec<BagState<String>> bufferState =
                      StateSpecs.bag(StringUtf8Coder.of());

                  @StateId(stateId2)
                  private final StateSpec<BagState<String>> bufferState2 =
                      StateSpecs.bag(StringUtf8Coder.of());

                  @ProcessElement
                  public void processElement(
                      @Element KV<String, String> element,
                      @StateId(stateId) BagState<String> state,
                      @StateId(stateId2) BagState<String> state2,
                      OutputReceiver<KV<String, String>> r) {
                    ReadableState<Boolean> isEmpty = state.isEmpty();
                    for (String value : state.read()) {
                      r.output(KV.of(element.getKey(), value));
                    }
                    state.add(element.getValue());
                    state2.clear();
                  }
                }))
        // Force the output to be materialized
        .apply("gbk", GroupByKey.create());

    RunnerApi.Pipeline pipelineProto = PipelineTranslation.toProto(p);
    FusedPipeline fused = GreedyPipelineFuser.fuse(pipelineProto);
    Optional<ExecutableStage> optionalStage =
        Iterables.tryFind(
            fused.getFusedStages(), (ExecutableStage stage) -> !stage.getUserStates().isEmpty());
    checkState(optionalStage.isPresent(), "Expected a stage with user state.");
    ExecutableStage stage = optionalStage.get();

    ExecutableProcessBundleDescriptor descriptor =
        ProcessBundleDescriptors.fromExecutableStage(
            "test_stage",
            stage,
            dataServer.getApiServiceDescriptor(),
            stateServer.getApiServiceDescriptor());

    BundleProcessor processor =
        controlClient.getProcessor(
            descriptor.getProcessBundleDescriptor(),
            descriptor.getRemoteInputDestinations(),
            stateDelegator);
    Map<Target, Coder<WindowedValue<?>>> outputTargets = descriptor.getOutputTargetCoders();
    Map<Target, Collection<WindowedValue<?>>> outputValues = new HashMap<>();
    Map<Target, RemoteOutputReceiver<?>> outputReceivers = new HashMap<>();
    for (Entry<Target, Coder<WindowedValue<?>>> targetCoder : outputTargets.entrySet()) {
      List<WindowedValue<?>> outputContents = Collections.synchronizedList(new ArrayList<>());
      outputValues.put(targetCoder.getKey(), outputContents);
      outputReceivers.put(
          targetCoder.getKey(),
          RemoteOutputReceiver.of(targetCoder.getValue(), outputContents::add));
    }

    Map<String, List<ByteString>> userStateData =
        ImmutableMap.of(
            stateId,
            new ArrayList(
                Arrays.asList(
                    ByteString.copyFrom(
                        CoderUtils.encodeToByteArray(
                            StringUtf8Coder.of(), "A", Coder.Context.NESTED)),
                    ByteString.copyFrom(
                        CoderUtils.encodeToByteArray(
                            StringUtf8Coder.of(), "B", Coder.Context.NESTED)),
                    ByteString.copyFrom(
                        CoderUtils.encodeToByteArray(
                            StringUtf8Coder.of(), "C", Coder.Context.NESTED)))),
            stateId2,
            new ArrayList(
                Arrays.asList(
                    ByteString.copyFrom(
                        CoderUtils.encodeToByteArray(
                            StringUtf8Coder.of(), "D", Coder.Context.NESTED)))));
    StateRequestHandler stateRequestHandler =
        StateRequestHandlers.forBagUserStateHandlerFactory(
            descriptor,
            new BagUserStateHandlerFactory() {
              @Override
              public <K, V, W extends BoundedWindow> BagUserStateHandler<K, V, W> forUserState(
                  String pTransformId,
                  String userStateId,
                  Coder<K> keyCoder,
                  Coder<V> valueCoder,
                  Coder<W> windowCoder) {
                return new BagUserStateHandler<K, V, W>() {
                  @Override
                  public Iterable<V> get(K key, W window) {
                    return (Iterable) userStateData.get(userStateId);
                  }

                  @Override
                  public void append(K key, W window, Iterator<V> values) {
                    Iterators.addAll(userStateData.get(userStateId), (Iterator) values);
                  }

                  @Override
                  public void clear(K key, W window) {
                    userStateData.get(userStateId).clear();
                  }
                };
              }
            });

    try (ActiveBundle bundle =
        processor.newBundle(
            outputReceivers, stateRequestHandler, BundleProgressHandler.ignored())) {
      Iterables.getOnlyElement(bundle.getInputReceivers().values())
          .accept(WindowedValue.valueInGlobalWindow(KV.of("X", "Y")));
    }
    for (Collection<WindowedValue<?>> windowedValues : outputValues.values()) {
      assertThat(
          windowedValues,
          containsInAnyOrder(
              WindowedValue.valueInGlobalWindow(KV.of("X", "A")),
              WindowedValue.valueInGlobalWindow(KV.of("X", "B")),
              WindowedValue.valueInGlobalWindow(KV.of("X", "C"))));
    }
    assertThat(
        userStateData.get(stateId),
        IsIterableContainingInOrder.contains(
            ByteString.copyFrom(
                CoderUtils.encodeToByteArray(StringUtf8Coder.of(), "A", Coder.Context.NESTED)),
            ByteString.copyFrom(
                CoderUtils.encodeToByteArray(StringUtf8Coder.of(), "B", Coder.Context.NESTED)),
            ByteString.copyFrom(
                CoderUtils.encodeToByteArray(StringUtf8Coder.of(), "C", Coder.Context.NESTED)),
            ByteString.copyFrom(
                CoderUtils.encodeToByteArray(StringUtf8Coder.of(), "Y", Coder.Context.NESTED))));
    assertThat(userStateData.get(stateId2), IsEmptyIterable.emptyIterable());
  }

  @Test
  public void testExecutionWithTimer() throws Exception {
    Pipeline p = Pipeline.create();
    final String timerId = "foo";
    final String timerId2 = "foo2";

    p.apply("impulse", Impulse.create())
        .apply(
            "create",
            ParDo.of(
                new DoFn<byte[], KV<String, String>>() {
                  @ProcessElement
                  public void process(ProcessContext ctxt) {}
                }))
        .setCoder(KvCoder.of(StringUtf8Coder.of(), StringUtf8Coder.of()))
        .apply(
            "timer",
            ParDo.of(
                new DoFn<KV<String, String>, KV<String, String>>() {
                  @TimerId("event")
                  private final TimerSpec eventTimerSpec = TimerSpecs.timer(TimeDomain.EVENT_TIME);

                  @TimerId("processing")
                  private final TimerSpec processingTimerSpec =
                      TimerSpecs.timer(TimeDomain.PROCESSING_TIME);

                  @ProcessElement
                  public void processElement(
                      ProcessContext context,
                      @TimerId("event") Timer eventTimeTimer,
                      @TimerId("processing") Timer processingTimeTimer) {
                    context.output(KV.of("main" + context.element().getKey(), ""));
                    eventTimeTimer.set(context.timestamp().plus(1L));
                    processingTimeTimer.offset(Duration.millis(2L));
                    processingTimeTimer.setRelative();
                  }

                  @OnTimer("event")
                  public void eventTimer(
                      OnTimerContext context,
                      @TimerId("event") Timer eventTimeTimer,
                      @TimerId("processing") Timer processingTimeTimer) {
                    context.output(KV.of("event", ""));
                    eventTimeTimer.set(context.timestamp().plus(11L));
                    processingTimeTimer.offset(Duration.millis(12L));
                    processingTimeTimer.setRelative();
                  }

                  @OnTimer("processing")
                  public void processingTimer(
                      OnTimerContext context,
                      @TimerId("event") Timer eventTimeTimer,
                      @TimerId("processing") Timer processingTimeTimer) {
                    context.output(KV.of("processing", ""));
                    eventTimeTimer.set(context.timestamp().plus(21L));
                    processingTimeTimer.offset(Duration.millis(22L));
                    processingTimeTimer.setRelative();
                  }
                }))
        // Force the output to be materialized
        .apply("gbk", GroupByKey.create());

    RunnerApi.Pipeline pipelineProto = PipelineTranslation.toProto(p);
    FusedPipeline fused = GreedyPipelineFuser.fuse(pipelineProto);
    Optional<ExecutableStage> optionalStage =
        Iterables.tryFind(
            fused.getFusedStages(), (ExecutableStage stage) -> !stage.getTimers().isEmpty());
    checkState(optionalStage.isPresent(), "Expected a stage with timers.");
    ExecutableStage stage = optionalStage.get();

    ExecutableProcessBundleDescriptor descriptor =
        ProcessBundleDescriptors.fromExecutableStage(
            "test_stage",
            stage,
            dataServer.getApiServiceDescriptor(),
            stateServer.getApiServiceDescriptor());

    BundleProcessor processor =
        controlClient.getProcessor(
            descriptor.getProcessBundleDescriptor(),
            descriptor.getRemoteInputDestinations(),
            stateDelegator);
    Map<Target, Coder<WindowedValue<?>>> outputTargets = descriptor.getOutputTargetCoders();
    Map<Target, Collection<WindowedValue<?>>> outputValues = new HashMap<>();
    Map<Target, RemoteOutputReceiver<?>> outputReceivers = new HashMap<>();
    for (Entry<Target, Coder<WindowedValue<?>>> targetCoder : outputTargets.entrySet()) {
      List<WindowedValue<?>> outputContents = Collections.synchronizedList(new ArrayList<>());
      outputValues.put(targetCoder.getKey(), outputContents);
      outputReceivers.put(
          targetCoder.getKey(),
          RemoteOutputReceiver.of(targetCoder.getValue(), outputContents::add));
    }

    String eventTimeInputPCollectionId = null;
    Target eventTimeOutputTarget = null;
    String processingTimeInputPCollectionId = null;
    Target processingTimeOutputTarget = null;
    for (Map<String, ProcessBundleDescriptors.TimerSpec> timerSpecs :
        descriptor.getTimerSpecs().values()) {
      for (ProcessBundleDescriptors.TimerSpec timerSpec : timerSpecs.values()) {
        if (TimeDomain.EVENT_TIME.equals(timerSpec.getTimerSpec().getTimeDomain())) {
          eventTimeInputPCollectionId = timerSpec.inputCollectionId();
          eventTimeOutputTarget = timerSpec.outputTarget();
        } else if (TimeDomain.PROCESSING_TIME.equals(timerSpec.getTimerSpec().getTimeDomain())) {
          processingTimeInputPCollectionId = timerSpec.inputCollectionId();
          processingTimeOutputTarget = timerSpec.outputTarget();
        } else {
          fail(String.format("Unknown timer specification %s", timerSpec));
        }
      }
    }

    // Set the current system time to a fixed value to get stable values for processing time timer
    // output.
    DateTimeUtils.setCurrentMillisFixed(BoundedWindow.TIMESTAMP_MIN_VALUE.getMillis());

    try (ActiveBundle bundle =
        processor.newBundle(
            outputReceivers, StateRequestHandler.unsupported(), BundleProgressHandler.ignored())) {
      bundle
          .getInputReceivers()
          .get(stage.getInputPCollection().getId())
          .accept(WindowedValue.valueInGlobalWindow(KV.of("X", "X")));
      bundle
          .getInputReceivers()
          .get(eventTimeInputPCollectionId)
          .accept(WindowedValue.valueInGlobalWindow(timerBytes("Y", 100L)));
      bundle
          .getInputReceivers()
          .get(processingTimeInputPCollectionId)
          .accept(WindowedValue.valueInGlobalWindow(timerBytes("Z", 200L)));
    }
    Set<Target> timerOutputTargets =
        ImmutableSet.of(eventTimeOutputTarget, processingTimeOutputTarget);
    Target mainOutputTarget =
        Iterables.getOnlyElement(
            Sets.difference(descriptor.getOutputTargetCoders().keySet(), timerOutputTargets));
    assertThat(
        outputValues.get(mainOutputTarget),
        containsInAnyOrder(
            WindowedValue.valueInGlobalWindow(KV.of("mainX", "")),
            WindowedValue.valueInGlobalWindow(KV.of("event", "")),
            WindowedValue.valueInGlobalWindow(KV.of("processing", ""))));
    assertThat(
        timerStructuralValues(outputValues.get(eventTimeOutputTarget)),
        containsInAnyOrder(
            timerStructuralValue(WindowedValue.valueInGlobalWindow(timerBytes("X", 1L))),
            timerStructuralValue(WindowedValue.valueInGlobalWindow(timerBytes("Y", 11L))),
            timerStructuralValue(WindowedValue.valueInGlobalWindow(timerBytes("Z", 21L)))));
    assertThat(
        timerStructuralValues(outputValues.get(processingTimeOutputTarget)),
        containsInAnyOrder(
            timerStructuralValue(WindowedValue.valueInGlobalWindow(timerBytes("X", 2L))),
            timerStructuralValue(WindowedValue.valueInGlobalWindow(timerBytes("Y", 12L))),
            timerStructuralValue(WindowedValue.valueInGlobalWindow(timerBytes("Z", 22L)))));
  }

  @Test
  public void testExecutionWithMultipleStages() throws Exception {
    Pipeline p = Pipeline.create();

    Function<String, PCollection<String>> pCollectionGenerator =
        suffix ->
            p.apply("impulse" + suffix, Impulse.create())
                .apply(
                    "create" + suffix,
                    ParDo.of(
                        new DoFn<byte[], String>() {
                          @ProcessElement
                          public void process(ProcessContext c) {
                            try {
                              c.output(
                                  CoderUtils.decodeFromByteArray(
                                      StringUtf8Coder.of(), c.element()));
                            } catch (CoderException e) {
                              throw new RuntimeException(e);
                            }
                          }
                        }))
                .setCoder(StringUtf8Coder.of())
                .apply(
                    ParDo.of(
                        new DoFn<String, String>() {
                          @ProcessElement
                          public void processElement(ProcessContext c) {
                            c.output("stream" + suffix + c.element());
                          }
                        }));
    PCollection<String> input1 = pCollectionGenerator.apply("1");
    PCollection<String> input2 = pCollectionGenerator.apply("2");

    PCollection<String> outputMerged =
        PCollectionList.of(input1).and(input2).apply(Flatten.pCollections());
    outputMerged
        .apply(
            "createKV",
            ParDo.of(
                new DoFn<String, KV<String, String>>() {
                  @ProcessElement
                  public void process(ProcessContext c) {
                    c.output(KV.of(c.element(), ""));
                  }
                }))
        .setCoder(KvCoder.of(StringUtf8Coder.of(), StringUtf8Coder.of()))
        .apply("gbk", GroupByKey.create());

    RunnerApi.Pipeline pipelineProto = PipelineTranslation.toProto(p);
    FusedPipeline fused = GreedyPipelineFuser.fuse(pipelineProto);
    Set<ExecutableStage> stages = fused.getFusedStages();

    assertThat(stages.size(), equalTo(2));

    List<WindowedValue<?>> outputValues = Collections.synchronizedList(new ArrayList<>());

    for (ExecutableStage stage : stages) {
      ExecutableProcessBundleDescriptor descriptor =
          ProcessBundleDescriptors.fromExecutableStage(
              stage.toString(),
              stage,
              dataServer.getApiServiceDescriptor(),
              stateServer.getApiServiceDescriptor());

      BundleProcessor processor =
          controlClient.getProcessor(
              descriptor.getProcessBundleDescriptor(),
              descriptor.getRemoteInputDestinations(),
              stateDelegator);
      Map<Target, Coder<WindowedValue<?>>> outputTargets = descriptor.getOutputTargetCoders();
      Map<Target, RemoteOutputReceiver<?>> outputReceivers = new HashMap<>();
      for (Entry<Target, Coder<WindowedValue<?>>> targetCoder : outputTargets.entrySet()) {
        outputReceivers.putIfAbsent(
            targetCoder.getKey(),
            RemoteOutputReceiver.of(targetCoder.getValue(), outputValues::add));
      }

      try (ActiveBundle bundle =
          processor.newBundle(
              outputReceivers,
              StateRequestHandler.unsupported(),
              BundleProgressHandler.ignored())) {
        bundle
            .getInputReceivers()
            .get(stage.getInputPCollection().getId())
            .accept(
                WindowedValue.valueInGlobalWindow(
                    CoderUtils.encodeToByteArray(StringUtf8Coder.of(), "X")));
      }
    }
    assertThat(
        outputValues,
        containsInAnyOrder(
            WindowedValue.valueInGlobalWindow(KV.of("stream1X", "")),
            WindowedValue.valueInGlobalWindow(KV.of("stream2X", ""))));
  }

  private KV<String, byte[]> byteValueOf(String key, long value) throws CoderException {
    return KV.of(key, CoderUtils.encodeToByteArray(BigEndianLongCoder.of(), value));
  }

  private KV<String, org.apache.beam.runners.core.construction.Timer<byte[]>> timerBytes(
      String key, long timestampOffset) throws CoderException {
    return KV.of(
        key,
        org.apache.beam.runners.core.construction.Timer.of(
            BoundedWindow.TIMESTAMP_MIN_VALUE.plus(timestampOffset),
            CoderUtils.encodeToByteArray(VoidCoder.of(), null, Coder.Context.NESTED)));
  }

  private Object timerStructuralValue(Object timer) {
    return WindowedValue.FullWindowedValueCoder.of(
            KvCoder.of(
                StringUtf8Coder.of(),
                org.apache.beam.runners.core.construction.Timer.Coder.of(ByteArrayCoder.of())),
            GlobalWindow.Coder.INSTANCE)
        .structuralValue(timer);
  }

  private Collection<Object> timerStructuralValues(Collection<?> timers) {
    return Collections2.transform(timers, this::timerStructuralValue);
  }
}