com.twitter.graphjet.demo.TopTweetsServlet.java Source code

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Here is the source code for com.twitter.graphjet.demo.TopTweetsServlet.java

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/**
 * Copyright 2016 Twitter. All rights reserved.
 *
 * 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 com.twitter.graphjet.demo;

import com.google.common.base.Joiner;
import com.google.common.collect.Lists;
import com.twitter.graphjet.bipartite.MultiSegmentPowerLawBipartiteGraph;
import it.unimi.dsi.fastutil.longs.LongIterator;
import it.unimi.dsi.fastutil.longs.LongSet;
import org.eclipse.jetty.http.HttpStatus;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.PriorityQueue;

/**
 * Servlet of {@link TwitterStreamReader} that returns the top <i>k</i> tweets in terms of degree in the user-tweet
 * bipartite graph.
 */
public class TopTweetsServlet extends HttpServlet {
    public enum GraphType {
        USER_TWEET, TWEET_HASHTAG
    }

    private static final Joiner JOINER = Joiner.on(",\n");
    private final MultiSegmentPowerLawBipartiteGraph bigraph;
    private final LongSet tweets;
    private final GraphType graphType;

    public TopTweetsServlet(MultiSegmentPowerLawBipartiteGraph bigraph, LongSet tweets, GraphType graphType) {
        this.bigraph = bigraph;
        this.tweets = tweets;
        this.graphType = graphType;
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        int k = 10;
        String p = request.getParameter("k");
        if (p != null) {
            try {
                k = Integer.parseInt(p);
            } catch (NumberFormatException e) {
                // Just eat it, don't need to worry.
            }
        }

        PriorityQueue<NodeValueEntry> queue = new PriorityQueue<>(k);
        LongIterator iter = tweets.iterator();
        while (iter.hasNext()) {
            long tweet = iter.nextLong();
            int cnt = graphType.equals(GraphType.USER_TWEET) ? bigraph.getRightNodeDegree(tweet)
                    : bigraph.getLeftNodeDegree(tweet);
            if (cnt == 1)
                continue;

            if (queue.size() < k) {
                queue.add(new NodeValueEntry(tweet, cnt));
            } else {
                NodeValueEntry peek = queue.peek();
                // Break ties by preferring higher tweetid (i.e., more recent tweet)
                if (cnt > peek.getValue() || (cnt == peek.getValue() && tweet > peek.getNode())) {
                    queue.poll();
                    queue.add(new NodeValueEntry(tweet, cnt));
                }
            }
        }

        if (queue.size() == 0) {
            response.getWriter().println("[]\n");
            return;
        }

        NodeValueEntry e;
        List<String> entries = new ArrayList<>(queue.size());
        while ((e = queue.poll()) != null) {
            // Note that we explicitly use id_str and treat the tweet id as a String. See:
            // https://dev.twitter.com/overview/api/twitter-ids-json-and-snowflake
            entries.add(String.format("{\"id_str\": \"%d\", \"cnt\": %d}", e.getNode(), e.getValue()));
        }

        response.setStatus(HttpStatus.OK_200);
        response.getWriter().println("[\n" + JOINER.join(Lists.reverse(entries)) + "\n]");
    }
}