co.cask.cdap.examples.wikipedia.WikipediaDataDownloader.java Source code

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Here is the source code for co.cask.cdap.examples.wikipedia.WikipediaDataDownloader.java

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/*
 * Copyright  2015-2016 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.examples.wikipedia;

import co.cask.cdap.api.Resources;
import co.cask.cdap.api.common.Bytes;
import co.cask.cdap.api.data.batch.Input;
import co.cask.cdap.api.data.batch.Output;
import co.cask.cdap.api.mapreduce.AbstractMapReduce;
import co.cask.cdap.api.mapreduce.MapReduceContext;
import co.cask.cdap.api.workflow.Value;
import co.cask.cdap.api.workflow.WorkflowToken;
import co.cask.common.http.HttpRequest;
import co.cask.common.http.HttpRequests;
import co.cask.common.http.HttpResponse;
import com.google.common.base.Charsets;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.net.URL;
import java.net.URLEncoder;

/**
 * MapReduce job that downloads wikipedia data and stores it in a dataset.
 */
public class WikipediaDataDownloader extends AbstractMapReduce {

    public static final String NAME = co.cask.cdap.examples.wikipedia.WikipediaDataDownloader.class.getSimpleName();

    @Override
    protected void configure() {
        setName(NAME);
        setDescription("A MapReduce program that downloads Wikipedia data and stores it into a dataset.");
        setMapperResources(new Resources(512));
    }

    @Override
    public void beforeSubmit(MapReduceContext context) throws Exception {
        Job job = context.getHadoopJob();
        job.setMapperClass(WikipediaDataDownloaderMapper.class);
        job.setNumReduceTasks(0);
        context.addInput(Input.ofDataset(WikipediaPipelineApp.PAGE_TITLES_DATASET));
        context.addOutput(Output.ofDataset(WikipediaPipelineApp.RAW_WIKIPEDIA_DATASET));
    }

    @Override
    public void onFinish(boolean succeeded, MapReduceContext context) throws Exception {
        WorkflowToken workflowToken = context.getWorkflowToken();
        if (workflowToken != null) {
            workflowToken.put("result", Value.of(succeeded));
        }
    }

    /**
     * Mapper that downloads Wikipedia data for each input record.
     */
    public static class WikipediaDataDownloaderMapper extends Mapper<byte[], byte[], byte[], byte[]> {
        private static final Logger LOG = LoggerFactory.getLogger(WikipediaDataDownloader.class);
        private static final String WIKI_URL_FORMAT = "https://en.wikipedia.org/w/api.php?action=query&titles=%s&prop=revisions&rvprop=content&format=json";

        @Override
        protected void map(byte[] key, byte[] value, Context context) throws IOException, InterruptedException {
            String rawWikiJson;
            try {
                rawWikiJson = downloadWikiData(Bytes.toString(value));
            } catch (IOException e) {
                LOG.warn("Exception while downloading wiki data {}. Skipping record.", e.getMessage());
                return;
            }

            context.write(key, Bytes.toBytes(rawWikiJson));
            context.getCounter("custom", "num.records").increment(1);
        }

        private String downloadWikiData(String page) throws IOException {
            String pageDetailsUrl = String.format(WIKI_URL_FORMAT,
                    URLEncoder.encode(page, Charsets.UTF_8.displayName()));
            HttpRequest request = HttpRequest.get(new URL(pageDetailsUrl)).build();
            HttpResponse httpResponse = HttpRequests.execute(request);
            String responseBody = httpResponse.getResponseBodyAsString();
            if (200 != httpResponse.getResponseCode()) {
                throw new IOException(responseBody);
            }
            return responseBody;
        }
    }
}