StreamBatchReadable.java

/*
 * Copyright © 2014-2016 Cask Data, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * 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 co.cask.cdap.api.data.stream;

import co.cask.cdap.api.annotation.Beta;
import co.cask.cdap.api.data.batch.BatchReadable;
import co.cask.cdap.api.data.batch.Input;
import co.cask.cdap.api.data.batch.Split;
import co.cask.cdap.api.data.batch.SplitReader;
import co.cask.cdap.api.data.format.FormatSpecification;
import co.cask.cdap.api.data.schema.Schema;
import co.cask.cdap.api.flow.flowlet.StreamEvent;
import co.cask.cdap.api.mapreduce.MapReduceContext;
import co.cask.cdap.api.stream.GenericStreamEventData;
import co.cask.cdap.api.stream.StreamEventDecoder;
import co.cask.cdap.internal.io.SchemaTypeAdapter;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

import java.io.UnsupportedEncodingException;
import java.net.URI;
import java.net.URLDecoder;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * This class is for using a Stream as input for a MapReduce program. 
 * 
 * <p>
 * An instance of this class should be set in the
 * {@link MapReduceContext} of the {@code beforeSubmit} method to use the Stream as input:
 * </p>
 * <pre><code>
 *   class MyMapReduce implements MapReduce {
 *       public void beforeSubmit(MapReduceContext context) {
 *         context.addInput(Input.ofStream("mystream"));
 *       }
 *   }
 * </code></pre>
 *
 * @deprecated as of version 3.4.0. Use {@link MapReduceContext#addInput(Input)}
 */
@Deprecated
public class StreamBatchReadable implements BatchReadable<Long, String> {
  private static final Gson GSON = new GsonBuilder()
    .registerTypeAdapter(Schema.class, new SchemaTypeAdapter())
    .create();
  private static final String START_TIME_KEY = "start";
  private static final String END_TIME_KEY = "end";
  private static final String DECODER_KEY = "decoder";
  private static final String BODY_FORMAT_KEY = "bodyFormat";

  private final URI uri;
  private final String streamName;
  private final long startTime;
  private final long endTime;
  private final String decoderType;
  private final FormatSpecification bodyFormatSpec;

  /**
   * Specifies to use the given stream as input of a MapReduce job. Same as calling
   * {@link #useStreamInput(co.cask.cdap.api.mapreduce.MapReduceContext, String, long, long)
   * useStreamInput(context, streamName, 0L, Long.MAX_VALUE)}
   */
  public static void useStreamInput(MapReduceContext context, String streamName) {
    useStreamInput(context, streamName, 0L, Long.MAX_VALUE);
  }

  /**
   * Specifies to use the given stream as input of a MapReduce job.
   * <p/>
   * The {@code Mapper} or {@code Reducer} class
   * that reads from the Stream needs to have the {@code KEYIN} type as {@code LongWritable}, which
   * will carry timestamp of the {@link StreamEvent}.
   * <p/>
   * The {@code VALUEIN} type can be {@code BytesWritable} or {@code Text}. For {@code Text} value type,
   * the {@link StreamEvent} body will be decoded as UTF-8 String.
   *
   * @param context The context of the MapReduce job
   * @param streamName Name of the stream
   * @param startTime Start timestamp in milliseconds (inclusive) of stream events provided to the job
   * @param endTime End timestamp in milliseconds (exclusive) of stream events provided to the job
   */
  public static void useStreamInput(MapReduceContext context, String streamName, long startTime, long endTime) {
    context.setInput(new StreamBatchReadable(streamName, startTime, endTime));
  }

  /**
   * Specifies to use the given stream as input of a MapReduce job, with a custom {@link StreamEventDecoder} to
   * decode {@link StreamEvent} into key/value pairs.
   *
   * @param context The context of the MapReduce job
   * @param streamName Name of the stream
   * @param startTime Start timestamp in milliseconds (inclusive) of stream events provided to the job
   * @param endTime End timestamp in milliseconds (exclusive) of stream events provided to the job
   * @param decoderType The {@link StreamEventDecoder} class for decoding {@link StreamEvent}
   */
  public static void useStreamInput(MapReduceContext context, String streamName,
                                    long startTime, long endTime, Class<? extends StreamEventDecoder> decoderType) {
    context.setInput(new StreamBatchReadable(streamName, startTime, endTime, decoderType));
  }

  /**
   * Specifies to use the given stream as input of a MapReduce job, using the given {@link FormatSpecification}
   * describing how to read the body of a stream. Using this method means your mapper must use a
   * mapreduce LongWritable as the map key and {@link GenericStreamEventData} as the map value.
   *
   * @param context The context of the MapReduce job
   * @param streamName Name of the stream
   * @param startTime Start timestamp in milliseconds (inclusive) of stream events provided to the job
   * @param endTime End timestamp in milliseconds (exclusive) of stream events provided to the job
   * @param bodyFormatSpec The {@link FormatSpecification} describing how the stream body should be read
   */
  public static void useStreamInput(MapReduceContext context, String streamName,
                                    long startTime, long endTime, FormatSpecification bodyFormatSpec) {
    context.setInput(new StreamBatchReadable(streamName, startTime, endTime, bodyFormatSpec));
  }

  /**
   * Constructs an {@link URI} that represents the stream input.
   *
   * @param streamName Name of the stream
   * @param arguments A map containing the arguments of the URI.
   */
  private static URI createStreamURI(String streamName, Map<String, Object> arguments) {
    // It forms the query string for all key/value pairs in the arguments map
    // It encodes both key and value using the URLEncoder
    try {
      StringBuilder builder = new StringBuilder();
      String sep = "";
      for (Map.Entry<String, Object> entry : arguments.entrySet()) {
        builder
          .append(sep)
          .append(URLEncoder.encode(entry.getKey(), "UTF-8"))
          .append("=")
          .append(URLEncoder.encode(entry.getValue().toString(), "UTF-8"));
        sep = "&";
      }
      return URI.create(String.format("stream://%s?%s", streamName, builder.toString()));
    } catch (UnsupportedEncodingException e) {
      // Shouldn't happen as UTF-8 should always supported.
      throw new RuntimeException(e);
    }
  }

  /**
   * Creates a StreamBatchReadable with the given URI. The URI should be of the form:
   *
   * <pre>{@code
   * stream://<stream_name>[?start=<start_time>[&end=<end_time>[&decoder=<decoderClass>[&bodyFormat=<bodyFormat>]]]]
   * }</pre>
   */
  public StreamBatchReadable(URI uri) {
    if (!"stream".equals(uri.getScheme())) {
      throw new IllegalArgumentException("Invalid stream URI " + uri);
    }
    this.uri = uri;
    streamName = uri.getAuthority();

    String query = uri.getQuery();
    if (query != null && !query.isEmpty()) {
      Map<String, String> parameters = new HashMap<>();
      for (String pair : query.split("&")) {
        int idx = pair.indexOf('=');
        String key = idx < 0 ? pair : pair.substring(0, idx);
        String value = idx < 0 ? "" : pair.substring(idx + 1);
        parameters.put(key, value);
      }

      startTime = parameters.containsKey(START_TIME_KEY) ? Long.parseLong(parameters.get(START_TIME_KEY)) : 0L;
      endTime = parameters.containsKey(END_TIME_KEY) ? Long.parseLong(parameters.get(END_TIME_KEY)) : Long.MAX_VALUE;
      decoderType = parameters.get(DECODER_KEY);
      bodyFormatSpec = decodeFormatSpec(parameters.get(BODY_FORMAT_KEY));
    } else {
      startTime = 0L;
      endTime = Long.MAX_VALUE;
      decoderType = null;
      bodyFormatSpec = null;
    }
  }

  /**
   * Constructs an instance with the given stream name with all time range.
   *
   * @param streamName Name of the stream.
   */
  public StreamBatchReadable(String streamName) {
    this(streamName, 0, Long.MAX_VALUE);
  }

  /**
   * Constructs an instance with the given properties.
   *
   * @param streamName Name of the stream.
   * @param startTime Start timestamp in milliseconds.
   * @param endTime End timestamp in milliseconds.
   */
  public StreamBatchReadable(String streamName, long startTime, long endTime) {
    this(createStreamURI(streamName, createArguments(START_TIME_KEY, startTime, END_TIME_KEY, endTime)));
  }

  /**
   * Constructs an instance with the given properties.
   *
   * @param streamName Name of the stream
   * @param startTime Start timestamp in milliseconds (inclusive) of stream events provided to the job
   * @param endTime End timestamp in milliseconds (exclusive) of stream events provided to the job
   * @param decoderType The {@link StreamEventDecoder} class for decoding {@link StreamEvent}
   */
  public StreamBatchReadable(String streamName, long startTime,
                             long endTime, Class<? extends StreamEventDecoder> decoderType) {
    this(createStreamURI(streamName, createArguments(START_TIME_KEY, startTime,
                                                     END_TIME_KEY, endTime,
                                                     DECODER_KEY, decoderType.getName())));
  }

  /**
   * Constructs an instance with the given properties.
   *
   * @param streamName Name of the stream
   * @param startTime Start timestamp in milliseconds (inclusive) of stream events provided to the job
   * @param endTime End timestamp in milliseconds (exclusive) of stream events provided to the job
   * @param bodyFormatSpec The {@link FormatSpecification} class for decoding {@link StreamEvent}
   */
  @Beta
  public StreamBatchReadable(String streamName, long startTime,
                             long endTime, FormatSpecification bodyFormatSpec) {
    this(createStreamURI(streamName, createArguments(START_TIME_KEY, startTime,
                                                     END_TIME_KEY, endTime,
                                                     BODY_FORMAT_KEY, encodeFormatSpec(bodyFormatSpec))));
  }

  /**
   * Returns the stream name.
   */
  public String getStreamName() {
    return streamName;
  }

  /**
   * Returns the start time.
   */
  public long getStartTime() {
    return startTime;
  }

  /**
   * Returns the end time.
   */
  public long getEndTime() {
    return endTime;
  }

  /**
   * Returns the class name of the decoder.
   */
  public String getDecoderType() {
    return decoderType;
  }

  /**
   * Returns the {@link FormatSpecification} for reading the body of the stream.
   */
  public FormatSpecification getFormatSpecification() {
    return bodyFormatSpec;
  }

  /**
   * Returns an {@link URI} that represents this {@link StreamBatchReadable}.
   */
  public URI toURI() {
    return uri;
  }

  @Override
  public List<Split> getSplits() {
    // Not used.
    return null;
  }

  @Override
  public SplitReader<Long, String> createSplitReader(Split split) {
    // Not used.
    return null;
  }

  private static String encodeFormatSpec(FormatSpecification formatSpecification) {
    String asJson = GSON.toJson(formatSpecification);
    try {
      return URLEncoder.encode(asJson, "UTF-8");
    } catch (UnsupportedEncodingException e) {
      // this should never happen
      throw new RuntimeException(e);
    }
  }

  private static FormatSpecification decodeFormatSpec(String encodedFormatSpecification) {
    if (encodedFormatSpecification == null) {
      return null;
    }
    try {
      String decodedFormatSpecification = URLDecoder.decode(encodedFormatSpecification, "UTF-8");
      return GSON.fromJson(decodedFormatSpecification, FormatSpecification.class);
    } catch (UnsupportedEncodingException e) {
      // this should never happen
      throw new RuntimeException(e);
    }
  }

  private static Map<String, Object> createArguments(Object...keyValues) {
    if (keyValues.length % 2 != 0) {
      throw new IllegalArgumentException("Expected keyValues of even size");
    }
    Map<String, Object> args = new HashMap<>();
    for (int i = 0; i < keyValues.length; i += 2) {
      args.put(keyValues[i].toString(), keyValues[i + 1]);
    }
    return args;
  }
}