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FindPeak.java
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FindPeak.java
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package offline;
import java.time.LocalTime;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.bson.Document;
import com.mongodb.Block;
import com.mongodb.MongoClient;
import com.mongodb.client.MapReduceIterable;
import com.mongodb.client.MongoDatabase;
import db.mongodb.MongoDBUtil;
public class FindPeak {
private static final String COLLECTION_NAME = "logs";
private static final String TIME = "time";
private static final String URL_PREFIX = "/EventRecommender";
private static List<LocalTime> buckets = initBuckets();
public static void main(String[] args) {
// Init
MongoClient mongoClient = new MongoClient();
MongoDatabase db = mongoClient.getDatabase(MongoDBUtil.DB_NAME);
StringBuilder sb = new StringBuilder();
sb.append("function() {");
sb.append("if (this.url.startsWith(\"");
sb.append(URL_PREFIX);
sb.append("\")) { emit(this.");
sb.append(TIME);
sb.append(".substring(0, 5), 1); }");
sb.append("}");
String map = sb.toString();
// Construct a reducer function
String reduce = "function(key, values) {return Array.sum(values)} ";
// MapReduce
MapReduceIterable<Document> results = db.getCollection(COLLECTION_NAME).mapReduce(map, reduce);//粒度每一分钟
// Save total count to each bucket --> 粒度每15分钟
Map<String, Double> timeMap = new HashMap<>();
results.forEach(new Block<Document>() {
@Override
public void apply(final Document document) {
String time = findBucket(document.getString("_id"));//Document{{_id=03:23, value=4.0}}
Double count = document.getDouble("value");
if (timeMap.containsKey(time)) {
timeMap.put(time, timeMap.get(time) + count);
} else {
timeMap.put(time, count);
}
}
});
// Need a sorting here
List<Map.Entry<String, Double>> timeList = new ArrayList<Map.Entry<String, Double>>(timeMap.entrySet());
Collections.sort(timeList, new Comparator<Map.Entry<String, Double>>() {
public int compare(Map.Entry<String, Double> o1, Map.Entry<String, Double> o2) {
if (o2.getValue().compareTo(o1.getValue()) > 0) {
return 1;
} else {
return -1;
}
}
});
printList(timeList);
mongoClient.close();
}
private static void printList(List<Map.Entry<String, Double>> timeList) {
for (Map.Entry<String, Double> entry : timeList) {
System.out.println("time: " + entry.getKey() + " count: " + entry.getValue());
}
}
private static List<LocalTime> initBuckets() {// 每15分钟最为一个bucket
List<LocalTime> buckets = new ArrayList<>();
LocalTime time = LocalTime.parse("00:00");
for (int i = 0; i < 96; ++i) {
buckets.add(time);
time = time.plusMinutes(15);
}
return buckets;
}
// Use LocalTime.isAfter/isBefore to compare to objects
// [“00:00”, “00:15”, “00:30”, … , “23:30”, “23:45”]
// “00:12”
private static String findBucket(String currentTime) {
LocalTime curr = LocalTime.parse(currentTime);
int left = 0, right = buckets.size() - 1;
while (left +1 < right) {
int mid = (left + right) / 2;
if (buckets.get(mid).isAfter(curr)) {
right = mid - 1;
} else {
left = mid;
}
}
if (buckets.get(right).isAfter(curr)) {
return buckets.get(left).toString();
}
return buckets.get(right).toString();
}
}