/*
 * 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.sdk.io.kinesis;

import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkArgument;

import com.amazonaws.regions.Regions;
import com.amazonaws.services.cloudwatch.AmazonCloudWatch;
import com.amazonaws.services.kinesis.AmazonKinesis;
import com.amazonaws.services.kinesis.clientlibrary.lib.worker.InitialPositionInStream;
import com.amazonaws.services.kinesis.producer.Attempt;
import com.amazonaws.services.kinesis.producer.IKinesisProducer;
import com.amazonaws.services.kinesis.producer.KinesisProducerConfiguration;
import com.amazonaws.services.kinesis.producer.UserRecordFailedException;
import com.amazonaws.services.kinesis.producer.UserRecordResult;
import com.google.auto.value.AutoValue;
import com.google.common.util.concurrent.ListenableFuture;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Properties;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.LinkedBlockingDeque;
import javax.annotation.Nullable;
import org.apache.beam.sdk.annotations.Experimental;
import org.apache.beam.sdk.io.Read.Unbounded;
import org.apache.beam.sdk.transforms.DoFn;
import org.apache.beam.sdk.transforms.PTransform;
import org.apache.beam.sdk.transforms.ParDo;
import org.apache.beam.sdk.values.PBegin;
import org.apache.beam.sdk.values.PCollection;
import org.apache.beam.sdk.values.PDone;
import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.annotations.VisibleForTesting;
import org.joda.time.Duration;
import org.joda.time.Instant;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * {@link PTransform}s for reading from and writing to <a
 * href="https://aws.amazon.com/kinesis/">Kinesis</a> streams.
 *
 * <h3>Reading from Kinesis</h3>
 *
 * <p>Example usage:
 *
 * <pre>{@code
 * p.apply(KinesisIO.read()
 *     .withStreamName("streamName")
 *     .withInitialPositionInStream(InitialPositionInStream.LATEST)
 *     .withAWSClientsProvider("AWS_KEY", _"AWS_SECRET", STREAM_REGION)
 *  .apply( ... ) // other transformations
 * }</pre>
 *
 * <p>As you can see you need to provide 3 things:
 *
 * <ul>
 *   <li>name of the stream you're going to read
 *   <li>position in the stream where reading should start. There are two options:
 *       <ul>
 *         <li>{@link InitialPositionInStream#LATEST} - reading will begin from end of the stream
 *         <li>{@link InitialPositionInStream#TRIM_HORIZON} - reading will begin at the very
 *             beginning of the stream
 *       </ul>
 *   <li>data used to initialize {@link AmazonKinesis} and {@link AmazonCloudWatch} clients:
 *       <ul>
 *         <li>credentials (aws key, aws secret)
 *         <li>region where the stream is located
 *       </ul>
 * </ul>
 *
 * <p>In case when you want to set up {@link AmazonKinesis} or {@link AmazonCloudWatch} client by
 * your own (for example if you're using more sophisticated authorization methods like Amazon STS,
 * etc.) you can do it by implementing {@link AWSClientsProvider} class:
 *
 * <pre>{@code
 * public class MyCustomKinesisClientProvider implements AWSClientsProvider {
 *   {@literal @}Override
 *   public AmazonKinesis getKinesisClient() {
 *     // set up your client here
 *   }
 *
 *   public AmazonCloudWatch getCloudWatchClient() {
 *     // set up your client here
 *   }
 *
 * }
 * }</pre>
 *
 * <p>Usage is pretty straightforward:
 *
 * <pre>{@code
 * p.apply(KinesisIO.read()
 *    .withStreamName("streamName")
 *    .withInitialPositionInStream(InitialPositionInStream.LATEST)
 *    .withAWSClientsProvider(new MyCustomKinesisClientProvider())
 *  .apply( ... ) // other transformations
 * }</pre>
 *
 * <p>There’s also possibility to start reading using arbitrary point in time - in this case you
 * need to provide {@link Instant} object:
 *
 * <pre>{@code
 * p.apply(KinesisIO.read()
 *     .withStreamName("streamName")
 *     .withInitialTimestampInStream(instant)
 *     .withAWSClientsProvider(new MyCustomKinesisClientProvider())
 *  .apply( ... ) // other transformations
 * }</pre>
 *
 * <p>Kinesis IO uses ArrivalTimeWatermarkPolicy by default. To use Processing time as event time:
 *
 * <pre>{@code
 * p.apply(KinesisIO.read()
 *    .withStreamName("streamName")
 *    .withInitialPositionInStream(InitialPositionInStream.LATEST)
 *    .withProcessingTimeWatermarkPolicy())
 * }</pre>
 *
 * <p>It is also possible to specify a custom watermark policy to control watermark computation.
 * Below is an example
 *
 * <pre>{@code
 * // custom policy
 * class MyCustomPolicy implements WatermarkPolicy {
 *     private WatermarkPolicyFactory.CustomWatermarkPolicy customWatermarkPolicy;
 *
 *     MyCustomPolicy() {
 *       this.customWatermarkPolicy = new WatermarkPolicyFactory.CustomWatermarkPolicy(WatermarkParameters.create());
 *     }
 *
 *     @Override
 *     public Instant getWatermark() {
 *       return customWatermarkPolicy.getWatermark();
 *     }
 *
 *     @Override
 *     public void update(KinesisRecord record) {
 *       customWatermarkPolicy.update(record);
 *     }
 *   }
 *
 * // custom factory
 * class MyCustomPolicyFactory implements WatermarkPolicyFactory {
 *     @Override
 *     public WatermarkPolicy createWatermarkPolicy() {
 *       return new MyCustomPolicy();
 *     }
 * }
 *
 * p.apply(KinesisIO.read()
 *    .withStreamName("streamName")
 *    .withInitialPositionInStream(InitialPositionInStream.LATEST)
 *    .withCustomWatermarkPolicy(new MyCustomPolicyFactory())
 * }</pre>
 *
 * <h3>Writing to Kinesis</h3>
 *
 * <p>Example usage:
 *
 * <pre>{@code
 * PCollection<byte[]> data = ...;
 *
 * data.apply(KinesisIO.write()
 *     .withStreamName("streamName")
 *     .withPartitionKey("partitionKey")
 *     .withAWSClientsProvider(AWS_KEY, AWS_SECRET, STREAM_REGION));
 * }</pre>
 *
 * <p>As a client, you need to provide at least 3 things:
 *
 * <ul>
 *   <li>name of the stream where you're going to write
 *   <li>partition key (or implementation of {@link KinesisPartitioner}) that defines which
 *       partition will be used for writing
 *   <li>data used to initialize {@link AmazonKinesis} and {@link AmazonCloudWatch} clients:
 *       <ul>
 *         <li>credentials (aws key, aws secret)
 *         <li>region where the stream is located
 *       </ul>
 * </ul>
 *
 * <p>In case if you need to define more complicated logic for key partitioning then you can create
 * your own implementation of {@link KinesisPartitioner} and set it by {@link
 * KinesisIO.Write#withPartitioner(KinesisPartitioner)}
 *
 * <p>Internally, {@link KinesisIO.Write} relies on Amazon Kinesis Producer Library (KPL). This
 * library can be configured with a set of {@link Properties} if needed.
 *
 * <p>Example usage of KPL configuration:
 *
 * <pre>{@code
 * Properties properties = new Properties();
 * properties.setProperty("KinesisEndpoint", "localhost");
 * properties.setProperty("KinesisPort", "4567");
 *
 * PCollection<byte[]> data = ...;
 *
 * data.apply(KinesisIO.write()
 *     .withStreamName("streamName")
 *     .withPartitionKey("partitionKey")
 *     .withAWSClientsProvider(AWS_KEY, AWS_SECRET, STREAM_REGION)
 *     .withProducerProperties(properties));
 * }</pre>
 *
 * <p>For more information about configuratiom parameters, see the <a
 * href="https://github.com/awslabs/amazon-kinesis-producer/blob/master/java/amazon-kinesis-producer-sample/default_config.properties">sample
 * of configuration file</a>.
 */
@Experimental(Experimental.Kind.SOURCE_SINK)
public final class KinesisIO {

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

  private static final int DEFAULT_NUM_RETRIES = 6;

  /** Returns a new {@link Read} transform for reading from Kinesis. */
  public static Read read() {
    return new AutoValue_KinesisIO_Read.Builder()
        .setMaxNumRecords(Long.MAX_VALUE)
        .setUpToDateThreshold(Duration.ZERO)
        .setWatermarkPolicyFactory(WatermarkPolicyFactory.withArrivalTimePolicy())
        .build();
  }

  /** A {@link PTransform} writing data to Kinesis. */
  public static Write write() {
    return new AutoValue_KinesisIO_Write.Builder().setRetries(DEFAULT_NUM_RETRIES).build();
  }

  /** Implementation of {@link #read}. */
  @AutoValue
  public abstract static class Read extends PTransform<PBegin, PCollection<KinesisRecord>> {

    @Nullable
    abstract String getStreamName();

    @Nullable
    abstract StartingPoint getInitialPosition();

    @Nullable
    abstract AWSClientsProvider getAWSClientsProvider();

    abstract long getMaxNumRecords();

    @Nullable
    abstract Duration getMaxReadTime();

    abstract Duration getUpToDateThreshold();

    @Nullable
    abstract Integer getRequestRecordsLimit();

    abstract WatermarkPolicyFactory getWatermarkPolicyFactory();

    abstract Builder toBuilder();

    @AutoValue.Builder
    abstract static class Builder {

      abstract Builder setStreamName(String streamName);

      abstract Builder setInitialPosition(StartingPoint startingPoint);

      abstract Builder setAWSClientsProvider(AWSClientsProvider clientProvider);

      abstract Builder setMaxNumRecords(long maxNumRecords);

      abstract Builder setMaxReadTime(Duration maxReadTime);

      abstract Builder setUpToDateThreshold(Duration upToDateThreshold);

      abstract Builder setRequestRecordsLimit(Integer limit);

      abstract Builder setWatermarkPolicyFactory(WatermarkPolicyFactory watermarkPolicyFactory);

      abstract Read build();
    }

    /** Specify reading from streamName. */
    public Read withStreamName(String streamName) {
      return toBuilder().setStreamName(streamName).build();
    }

    /** Specify reading from some initial position in stream. */
    public Read withInitialPositionInStream(InitialPositionInStream initialPosition) {
      return toBuilder().setInitialPosition(new StartingPoint(initialPosition)).build();
    }

    /**
     * Specify reading beginning at given {@link Instant}. This {@link Instant} must be in the past,
     * i.e. before {@link Instant#now()}.
     */
    public Read withInitialTimestampInStream(Instant initialTimestamp) {
      return toBuilder().setInitialPosition(new StartingPoint(initialTimestamp)).build();
    }

    /**
     * Allows to specify custom {@link AWSClientsProvider}. {@link AWSClientsProvider} provides
     * {@link AmazonKinesis} and {@link AmazonCloudWatch} instances which are later used for
     * communication with Kinesis. You should use this method if {@link
     * Read#withAWSClientsProvider(String, String, Regions)} does not suit your needs.
     */
    public Read withAWSClientsProvider(AWSClientsProvider awsClientsProvider) {
      return toBuilder().setAWSClientsProvider(awsClientsProvider).build();
    }

    /**
     * Specify credential details and region to be used to read from Kinesis. If you need more
     * sophisticated credential protocol, then you should look at {@link
     * Read#withAWSClientsProvider(AWSClientsProvider)}.
     */
    public Read withAWSClientsProvider(String awsAccessKey, String awsSecretKey, Regions region) {
      return withAWSClientsProvider(awsAccessKey, awsSecretKey, region, null);
    }

    /**
     * Specify credential details and region to be used to read from Kinesis. If you need more
     * sophisticated credential protocol, then you should look at {@link
     * Read#withAWSClientsProvider(AWSClientsProvider)}.
     *
     * <p>The {@code serviceEndpoint} sets an alternative service host. This is useful to execute
     * the tests with a kinesis service emulator.
     */
    public Read withAWSClientsProvider(
        String awsAccessKey, String awsSecretKey, Regions region, String serviceEndpoint) {
      return withAWSClientsProvider(
          new BasicKinesisProvider(awsAccessKey, awsSecretKey, region, serviceEndpoint));
    }

    /** Specifies to read at most a given number of records. */
    public Read withMaxNumRecords(long maxNumRecords) {
      checkArgument(
          maxNumRecords > 0, "maxNumRecords must be positive, but was: %s", maxNumRecords);
      return toBuilder().setMaxNumRecords(maxNumRecords).build();
    }

    /** Specifies to read records during {@code maxReadTime}. */
    public Read withMaxReadTime(Duration maxReadTime) {
      checkArgument(maxReadTime != null, "maxReadTime can not be null");
      return toBuilder().setMaxReadTime(maxReadTime).build();
    }

    /**
     * Specifies how late records consumed by this source can be to still be considered on time.
     * When this limit is exceeded the actual backlog size will be evaluated and the runner might
     * decide to scale the amount of resources allocated to the pipeline in order to speed up
     * ingestion.
     */
    public Read withUpToDateThreshold(Duration upToDateThreshold) {
      checkArgument(upToDateThreshold != null, "upToDateThreshold can not be null");
      return toBuilder().setUpToDateThreshold(upToDateThreshold).build();
    }

    /**
     * Specifies the maximum number of records in GetRecordsResult returned by GetRecords call which
     * is limited by 10K records. If should be adjusted according to average size of data record to
     * prevent shard overloading. More details can be found here: <a
     * href="https://docs.aws.amazon.com/kinesis/latest/APIReference/API_GetRecords.html">API_GetRecords</a>
     */
    public Read withRequestRecordsLimit(int limit) {
      checkArgument(limit > 0, "limit must be positive, but was: %s", limit);
      checkArgument(limit <= 10_000, "limit must be up to 10,000, but was: %s", limit);
      return toBuilder().setRequestRecordsLimit(limit).build();
    }

    /** Specifies the {@code WatermarkPolicyFactory} as ArrivalTimeWatermarkPolicyFactory. */
    public Read withArrivalTimeWatermarkPolicy() {
      return toBuilder()
          .setWatermarkPolicyFactory(WatermarkPolicyFactory.withArrivalTimePolicy())
          .build();
    }

    /**
     * Specifies the {@code WatermarkPolicyFactory} as ArrivalTimeWatermarkPolicyFactory.
     *
     * <p>{@param watermarkIdleDurationThreshold} Denotes the duration for which the watermark can
     * be idle.
     */
    public Read withArrivalTimeWatermarkPolicy(Duration watermarkIdleDurationThreshold) {
      return toBuilder()
          .setWatermarkPolicyFactory(
              WatermarkPolicyFactory.withArrivalTimePolicy(watermarkIdleDurationThreshold))
          .build();
    }

    /** Specifies the {@code WatermarkPolicyFactory} as ProcessingTimeWatermarkPolicyFactory. */
    public Read withProcessingTimeWatermarkPolicy() {
      return toBuilder()
          .setWatermarkPolicyFactory(WatermarkPolicyFactory.withProcessingTimePolicy())
          .build();
    }

    /**
     * Specifies the {@code WatermarkPolicyFactory} as a custom watermarkPolicyFactory.
     *
     * @param watermarkPolicyFactory Custom Watermark policy factory.
     */
    public Read withCustomWatermarkPolicy(WatermarkPolicyFactory watermarkPolicyFactory) {
      checkArgument(watermarkPolicyFactory != null, "watermarkPolicyFactory cannot be null");
      return toBuilder().setWatermarkPolicyFactory(watermarkPolicyFactory).build();
    }

    @Override
    public PCollection<KinesisRecord> expand(PBegin input) {
      Unbounded<KinesisRecord> unbounded =
          org.apache.beam.sdk.io.Read.from(
              new KinesisSource(
                  getAWSClientsProvider(),
                  getStreamName(),
                  getInitialPosition(),
                  getUpToDateThreshold(),
                  getWatermarkPolicyFactory(),
                  getRequestRecordsLimit()));

      PTransform<PBegin, PCollection<KinesisRecord>> transform = unbounded;

      if (getMaxNumRecords() < Long.MAX_VALUE || getMaxReadTime() != null) {
        transform =
            unbounded.withMaxReadTime(getMaxReadTime()).withMaxNumRecords(getMaxNumRecords());
      }

      return input.apply(transform);
    }
  }

  /** Implementation of {@link #write}. */
  @AutoValue
  public abstract static class Write extends PTransform<PCollection<byte[]>, PDone> {
    @Nullable
    abstract String getStreamName();

    @Nullable
    abstract String getPartitionKey();

    @Nullable
    abstract KinesisPartitioner getPartitioner();

    @Nullable
    abstract Properties getProducerProperties();

    @Nullable
    abstract AWSClientsProvider getAWSClientsProvider();

    abstract int getRetries();

    abstract Builder builder();

    @AutoValue.Builder
    abstract static class Builder {
      abstract Builder setStreamName(String streamName);

      abstract Builder setPartitionKey(String partitionKey);

      abstract Builder setPartitioner(KinesisPartitioner partitioner);

      abstract Builder setProducerProperties(Properties properties);

      abstract Builder setAWSClientsProvider(AWSClientsProvider clientProvider);

      abstract Builder setRetries(int retries);

      abstract Write build();
    }

    /** Specify Kinesis stream name which will be used for writing, this name is required. */
    public Write withStreamName(String streamName) {
      return builder().setStreamName(streamName).build();
    }

    /**
     * Specify default partition key.
     *
     * <p>In case if you need to define more complicated logic for key partitioning then you can
     * create your own implementation of {@link KinesisPartitioner} and specify it by {@link
     * KinesisIO.Write#withPartitioner(KinesisPartitioner)}
     *
     * <p>Using one of the methods {@link KinesisIO.Write#withPartitioner(KinesisPartitioner)} or
     * {@link KinesisIO.Write#withPartitionKey(String)} is required but not both in the same time.
     */
    public Write withPartitionKey(String partitionKey) {
      return builder().setPartitionKey(partitionKey).build();
    }

    /**
     * Allows to specify custom implementation of {@link KinesisPartitioner}.
     *
     * <p>This method should be used to balance a distribution of new written records among all
     * stream shards.
     *
     * <p>Using one of the methods {@link KinesisIO.Write#withPartitioner(KinesisPartitioner)} or
     * {@link KinesisIO.Write#withPartitionKey(String)} is required but not both in the same time.
     */
    public Write withPartitioner(KinesisPartitioner partitioner) {
      return builder().setPartitioner(partitioner).build();
    }

    /**
     * Specify the configuration properties for Kinesis Producer Library (KPL).
     *
     * <p>Example of creating new KPL configuration:
     *
     * <p>{@code Properties properties = new Properties();
     * properties.setProperty("CollectionMaxCount", "1000");
     * properties.setProperty("ConnectTimeout", "10000");}
     */
    public Write withProducerProperties(Properties properties) {
      return builder().setProducerProperties(properties).build();
    }

    /**
     * Allows to specify custom {@link AWSClientsProvider}. {@link AWSClientsProvider} creates new
     * {@link IKinesisProducer} which is later used for writing to Kinesis.
     *
     * <p>This method should be used if {@link Write#withAWSClientsProvider(String, String,
     * Regions)} does not suit well.
     */
    public Write withAWSClientsProvider(AWSClientsProvider awsClientsProvider) {
      return builder().setAWSClientsProvider(awsClientsProvider).build();
    }

    /**
     * Specify credential details and region to be used to write to Kinesis. If you need more
     * sophisticated credential protocol, then you should look at {@link
     * Write#withAWSClientsProvider(AWSClientsProvider)}.
     */
    public Write withAWSClientsProvider(String awsAccessKey, String awsSecretKey, Regions region) {
      return withAWSClientsProvider(awsAccessKey, awsSecretKey, region, null);
    }

    /**
     * Specify credential details and region to be used to write to Kinesis. If you need more
     * sophisticated credential protocol, then you should look at {@link
     * Write#withAWSClientsProvider(AWSClientsProvider)}.
     *
     * <p>The {@code serviceEndpoint} sets an alternative service host. This is useful to execute
     * the tests with Kinesis service emulator.
     */
    public Write withAWSClientsProvider(
        String awsAccessKey, String awsSecretKey, Regions region, String serviceEndpoint) {
      return withAWSClientsProvider(
          new BasicKinesisProvider(awsAccessKey, awsSecretKey, region, serviceEndpoint));
    }

    /**
     * Specify the number of retries that will be used to flush the outstanding records in case if
     * they were not flushed from the first time. Default number of retries is {@code
     * DEFAULT_NUM_RETRIES = 10}.
     *
     * <p>This is used for testing.
     */
    @VisibleForTesting
    Write withRetries(int retries) {
      return builder().setRetries(retries).build();
    }

    @Override
    public PDone expand(PCollection<byte[]> input) {
      checkArgument(getStreamName() != null, "withStreamName() is required");
      checkArgument(
          (getPartitionKey() != null) || (getPartitioner() != null),
          "withPartitionKey() or withPartitioner() is required");
      checkArgument(
          getPartitionKey() == null || (getPartitioner() == null),
          "only one of either withPartitionKey() or withPartitioner() is possible");
      checkArgument(getAWSClientsProvider() != null, "withAWSClientsProvider() is required");

      input.apply(ParDo.of(new KinesisWriterFn(this)));
      return PDone.in(input.getPipeline());
    }

    private static class KinesisWriterFn extends DoFn<byte[], Void> {

      private static final int MAX_NUM_FAILURES = 10;

      private final KinesisIO.Write spec;
      private static transient IKinesisProducer producer;
      private transient KinesisPartitioner partitioner;
      private transient LinkedBlockingDeque<KinesisWriteException> failures;
      private transient List<Future<UserRecordResult>> putFutures;

      KinesisWriterFn(KinesisIO.Write spec) {
        this.spec = spec;
        initKinesisProducer();
      }

      @Setup
      public void setup() {
        // Use custom partitioner if it exists
        if (spec.getPartitioner() != null) {
          partitioner = spec.getPartitioner();
        }
      }

      @StartBundle
      public void startBundle() {
        putFutures = Collections.synchronizedList(new ArrayList<>());
        /** Keep only the first {@link MAX_NUM_FAILURES} occurred exceptions */
        failures = new LinkedBlockingDeque<>(MAX_NUM_FAILURES);
        initKinesisProducer();
      }

      private synchronized void initKinesisProducer() {
        // Init producer config
        Properties props = spec.getProducerProperties();
        if (props == null) {
          props = new Properties();
        }
        KinesisProducerConfiguration config = KinesisProducerConfiguration.fromProperties(props);
        // Fix to avoid the following message "WARNING: Exception during updateCredentials" during
        // producer.destroy() call. More details can be found in this thread:
        // https://github.com/awslabs/amazon-kinesis-producer/issues/10
        config.setCredentialsRefreshDelay(100);

        // Init Kinesis producer
        if (producer == null) {
          producer = spec.getAWSClientsProvider().createKinesisProducer(config);
        }
      }

      private void readObject(ObjectInputStream is) throws IOException, ClassNotFoundException {
        is.defaultReadObject();
        initKinesisProducer();
      }

      /**
       * It adds a record asynchronously which then should be delivered by Kinesis producer in
       * background (Kinesis producer forks native processes to do this job).
       *
       * <p>The records can be batched and then they will be sent in one HTTP request. Amazon KPL
       * supports two types of batching - aggregation and collection - and they can be configured by
       * producer properties.
       *
       * <p>More details can be found here: <a
       * href="https://docs.aws.amazon.com/streams/latest/dev/kinesis-kpl-concepts.html">KPL Key
       * Concepts</a> and <a
       * href="https://docs.aws.amazon.com/streams/latest/dev/kinesis-kpl-config.html">Configuring
       * the KPL</a>
       */
      @ProcessElement
      public void processElement(ProcessContext c) {
        ByteBuffer data = ByteBuffer.wrap(c.element());
        String partitionKey = spec.getPartitionKey();
        String explicitHashKey = null;

        // Use custom partitioner
        if (partitioner != null) {
          partitionKey = partitioner.getPartitionKey(c.element());
          explicitHashKey = partitioner.getExplicitHashKey(c.element());
        }

        ListenableFuture<UserRecordResult> f =
            producer.addUserRecord(spec.getStreamName(), partitionKey, explicitHashKey, data);
        putFutures.add(f);
      }

      @FinishBundle
      public void finishBundle() throws Exception {
        flushBundle();
      }

      /**
       * Flush outstanding records until the total number of failed records will be less than 0 or
       * the number of retries will be exhausted. The retry timeout starts from 1 second and it
       * doubles on every iteration.
       */
      private void flushBundle() throws InterruptedException, ExecutionException, IOException {
        int retries = spec.getRetries();
        int numFailedRecords;
        int retryTimeout = 1000; // initial timeout, 1 sec
        String message = "";

        do {
          numFailedRecords = 0;
          producer.flush();

          // Wait for puts to finish and check the results
          for (Future<UserRecordResult> f : putFutures) {
            UserRecordResult result = f.get(); // this does block
            if (!result.isSuccessful()) {
              numFailedRecords++;
            }
          }

          // wait until outstanding records will be flushed
          Thread.sleep(retryTimeout);
          retryTimeout *= 2; // exponential backoff
        } while (numFailedRecords > 0 && retries-- > 0);

        if (numFailedRecords > 0) {
          for (Future<UserRecordResult> f : putFutures) {
            UserRecordResult result = f.get();
            if (!result.isSuccessful()) {
              failures.offer(
                  new KinesisWriteException(
                      "Put record was not successful.", new UserRecordFailedException(result)));
            }
          }

          message =
              String.format(
                  "After [%d] retries, number of failed records [%d] is still greater than 0",
                  spec.getRetries(), numFailedRecords);
          LOG.error(message);
        }

        checkForFailures(message);
      }

      /** If any write has asynchronously failed, fail the bundle with a useful error. */
      private void checkForFailures(String message) throws IOException {
        if (failures.isEmpty()) {
          return;
        }

        StringBuilder logEntry = new StringBuilder();
        logEntry.append(message).append(System.lineSeparator());

        int i = 0;
        while (!failures.isEmpty()) {
          i++;
          KinesisWriteException exc = failures.remove();

          logEntry.append(System.lineSeparator()).append(exc.getMessage());
          Throwable cause = exc.getCause();
          if (cause != null) {
            logEntry.append(": ").append(cause.getMessage());

            if (cause instanceof UserRecordFailedException) {
              List<Attempt> attempts =
                  ((UserRecordFailedException) cause).getResult().getAttempts();
              for (Attempt attempt : attempts) {
                if (attempt.getErrorMessage() != null) {
                  logEntry.append(System.lineSeparator()).append(attempt.getErrorMessage());
                }
              }
            }
          }
        }

        String errorMessage =
            String.format(
                "Some errors occurred writing to Kinesis. First %d errors: %s",
                i, logEntry.toString());
        throw new IOException(errorMessage);
      }

      @Teardown
      public void teardown() throws Exception {
        if (producer != null && producer.getOutstandingRecordsCount() > 0) {
          producer.flushSync();
        }
        producer = null;
      }
    }
  }

  /** An exception that puts information about the failed record. */
  static class KinesisWriteException extends IOException {
    KinesisWriteException(String message, Throwable cause) {
      super(message, cause);
    }
  }
}