test/unit/org/apache/cassandra/utils/StreamingHistogramTest.java

/*
 * 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.cassandra.utils;

import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;

import org.junit.Test;

import org.apache.cassandra.io.util.DataInputBuffer;
import org.apache.cassandra.io.util.DataOutputBuffer;

import static org.junit.Assert.assertEquals;

public class StreamingHistogramTest
{
    @Test
    public void testFunction() throws Exception
    {
        StreamingHistogram.StreamingHistogramBuilder histogramBuilder = new StreamingHistogram.StreamingHistogramBuilder(5, 0, 1);
        long[] samples = new long[]{23, 19, 10, 16, 36, 2, 9, 32, 30, 45};

        // add 7 points to histogram of 5 bins
        for (int i = 0; i < 7; i++)
        {
            histogramBuilder.update(samples[i]);
        }

        // should end up (2,1),(9.5,2),(17.5,2),(23,1),(36,1)
        Map<Double, Long> expected1 = new LinkedHashMap<Double, Long>(5);
        expected1.put(2.0, 1L);
        expected1.put(9.5, 2L);
        expected1.put(17.5, 2L);
        expected1.put(23.0, 1L);
        expected1.put(36.0, 1L);

        Iterator<Map.Entry<Double, Long>> expectedItr = expected1.entrySet().iterator();
        for (Map.Entry<Number, long[]> actual : histogramBuilder.build().getAsMap().entrySet())
        {
            Map.Entry<Double, Long> entry = expectedItr.next();
            assertEquals(entry.getKey(), actual.getKey().doubleValue(), 0.01);
            assertEquals(entry.getValue().longValue(), actual.getValue()[0]);
        }

        // merge test
        StreamingHistogram.StreamingHistogramBuilder hist2 = new StreamingHistogram.StreamingHistogramBuilder(3, 3, 1);
        for (int i = 7; i < samples.length; i++)
        {
            hist2.update(samples[i]);
        }
        histogramBuilder.merge(hist2.build());
        // should end up (2,1),(9.5,2),(19.33,3),(32.67,3),(45,1)
        Map<Double, Long> expected2 = new LinkedHashMap<Double, Long>(5);
        expected2.put(2.0, 1L);
        expected2.put(9.5, 2L);
        expected2.put(19.33, 3L);
        expected2.put(32.67, 3L);
        expected2.put(45.0, 1L);
        expectedItr = expected2.entrySet().iterator();
        StreamingHistogram hist = histogramBuilder.build();
        for (Map.Entry<Number, long[]> actual : hist.getAsMap().entrySet())
        {
            Map.Entry<Double, Long> entry = expectedItr.next();
            assertEquals(entry.getKey(), actual.getKey().doubleValue(), 0.01);
            assertEquals(entry.getValue().longValue(), actual.getValue()[0]);
        }

        // sum test
        assertEquals(3.28, hist.sum(15), 0.01);
        // sum test (b > max(hist))
        assertEquals(10.0, hist.sum(50), 0.01);
    }

    @Test
    public void testSerDe() throws Exception
    {
        StreamingHistogram.StreamingHistogramBuilder hist = new StreamingHistogram.StreamingHistogramBuilder(5, 0, 1);
        long[] samples = new long[]{23, 19, 10, 16, 36, 2, 9};

        // add 7 points to histogram of 5 bins
        for (int i = 0; i < samples.length; i++)
        {
            hist.update(samples[i]);
        }

        DataOutputBuffer out = new DataOutputBuffer();
        StreamingHistogram.serializer.serialize(hist.build(), out);
        byte[] bytes = out.toByteArray();

        StreamingHistogram deserialized = StreamingHistogram.serializer.deserialize(new DataInputBuffer(bytes));

        // deserialized histogram should have following values
        Map<Double, Long> expected1 = new LinkedHashMap<Double, Long>(5);
        expected1.put(2.0, 1L);
        expected1.put(9.5, 2L);
        expected1.put(17.5, 2L);
        expected1.put(23.0, 1L);
        expected1.put(36.0, 1L);

        Iterator<Map.Entry<Double, Long>> expectedItr = expected1.entrySet().iterator();
        for (Map.Entry<Number, long[]> actual : deserialized.getAsMap().entrySet())
        {
            Map.Entry<Double, Long> entry = expectedItr.next();
            assertEquals(entry.getKey(), actual.getKey().doubleValue(), 0.01);
            assertEquals(entry.getValue().longValue(), actual.getValue()[0]);
        }
    }


    @Test
    public void testNumericTypes() throws Exception
    {
        StreamingHistogram.StreamingHistogramBuilder hist = new StreamingHistogram.StreamingHistogramBuilder(5, 0, 1);

        hist.update(2);
        hist.update(2.0);
        hist.update(2L);

        Map<Number, long[]> asMap = hist.build().getAsMap();

        assertEquals(1, asMap.size());
        assertEquals(3L, asMap.get(2)[0]);

        //Make sure it's working with Serde
        DataOutputBuffer out = new DataOutputBuffer();
        StreamingHistogram.serializer.serialize(hist.build(), out);
        byte[] bytes = out.toByteArray();

        StreamingHistogram deserialized = StreamingHistogram.serializer.deserialize(new DataInputBuffer(bytes));

        StreamingHistogram.StreamingHistogramBuilder hist2Builder = new StreamingHistogram.StreamingHistogramBuilder(5, 0, 1);
        hist2Builder.merge(deserialized);
        hist2Builder.update(2L);

        asMap = hist2Builder.build().getAsMap();
        assertEquals(1, asMap.size());
        assertEquals(4L, asMap.get(2)[0]);
    }

    @Test
    public void testOverflow() throws Exception
    {
        StreamingHistogram.StreamingHistogramBuilder hist = new StreamingHistogram.StreamingHistogramBuilder(5, 10, 1);
        long[] samples = new long[]{23, 19, 10, 16, 36, 2, 9, 32, 30, 45, 31,
                                    32, 32, 33, 34, 35, 70, 78, 80, 90, 100,
                                    32, 32, 33, 34, 35, 70, 78, 80, 90, 100
                                    };

        // Hit the spool cap, force it to make bins
        for (int i = 0; i < samples.length; i++)
        {
            hist.update(samples[i]);
        }
        StreamingHistogram histogram = hist.build();
        assertEquals(5, histogram.getAsMap().keySet().size());

    }

    @Test
    public void testRounding() throws Exception
    {
        StreamingHistogram.StreamingHistogramBuilder hist = new StreamingHistogram.StreamingHistogramBuilder(5, 10, 60);
        long[] samples = new long[] { 59, 60, 119, 180, 181, 300 }; // 60, 60, 120, 180, 240, 300
        for (int i = 0 ; i < samples.length ; i++)
            hist.update(samples[i]);

        StreamingHistogram histogram = hist.build();
        assertEquals(histogram.getAsMap().keySet().size(), 5);
        assertEquals(histogram.getAsMap().get(60)[0], 2);
        assertEquals(histogram.getAsMap().get(120)[0], 1);

    }
}