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[core] Add the RandomDiscreteTimestampGenerator to generate a range of
timestamps in a non-repeating random order. Modify UnixEpochTimestampGenerator so that the random generator can extend it.
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core/src/main/java/com/yahoo/ycsb/generator/RandomDiscreteTimestampGenerator.java
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| /** | ||
| * Copyright (c) 2017 YCSB contributors. All rights reserved. | ||
| * <p> | ||
| * 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 | ||
| * <p> | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * <p> | ||
| * 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. See accompanying | ||
| * LICENSE file. | ||
| */ | ||
| package com.yahoo.ycsb.generator; | ||
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| import java.util.concurrent.TimeUnit; | ||
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| import com.yahoo.ycsb.Utils; | ||
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| /** | ||
| * A generator that picks from a discrete set of offsets from a base Unix Epoch | ||
| * timestamp that returns timestamps in a random order with the guarantee that | ||
| * each timestamp is only returned once. | ||
| * <p> | ||
| * TODO - It would be best to implement some kind of psuedo non-repeating random | ||
| * generator for this as it's likely OK that some small percentage of values are | ||
| * repeated. For now we just generate all of the offsets in an array, shuffle | ||
| * it and then iterate over the array. | ||
| * <p> | ||
| * Note that {@link #MAX_INTERVALS} defines a hard limit on the size of the | ||
| * offset array so that we don't completely blow out the heap. | ||
| * <p> | ||
| * The constructor parameter {@code intervals} determines how many values will be | ||
| * returned by the generator. For example, if the {@code interval} is 60 and the | ||
| * {@code timeUnits} are set to {@link TimeUnit#SECONDS} and {@code intervals} | ||
| * is set to 60, then the consumer can call {@link #nextValue()} 60 times for | ||
| * timestamps within an hour. | ||
| */ | ||
| public class RandomDiscreteTimestampGenerator extends UnixEpochTimestampGenerator { | ||
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| /** A hard limit on the size of the offsets array to a void using too much heap. */ | ||
| public static final int MAX_INTERVALS = 16777216; | ||
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| /** The total number of intervals for this generator. */ | ||
| private final int intervals; | ||
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| // can't be primitives due to the generic params on the sort function :( | ||
| /** The array of generated offsets from the base time. */ | ||
| private final Integer[] offsets; | ||
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| /** The current index into the offsets array. */ | ||
| private int offsetIndex; | ||
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| /** | ||
| * Ctor that uses the current system time as current. | ||
| * @param interval The interval between timestamps. | ||
| * @param timeUnits The time units of the returned Unix Epoch timestamp (as well | ||
| * as the units for the interval). | ||
| * @param intervals The total number of intervals for the generator. | ||
| * @throws IllegalArgumentException if the intervals is larger than {@link #MAX_INTERVALS} | ||
| */ | ||
| public RandomDiscreteTimestampGenerator(final long interval, final TimeUnit timeUnits, | ||
| final int intervals) { | ||
| super(interval, timeUnits); | ||
| this.intervals = intervals; | ||
| offsets = new Integer[intervals]; | ||
| setup(); | ||
| } | ||
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| /** | ||
| * Ctor for supplying a starting timestamp. | ||
| * The interval between timestamps. | ||
| * @param timeUnits The time units of the returned Unix Epoch timestamp (as well | ||
| * as the units for the interval). | ||
| * @param startTimestamp The start timestamp to use. | ||
| * NOTE that this must match the time units used for the interval. | ||
| * If the units are in nanoseconds, provide a nanosecond timestamp {@code System.nanoTime()} | ||
| * or in microseconds, {@code System.nanoTime() / 1000} | ||
| * or in millis, {@code System.currentTimeMillis()} | ||
| * @param intervals The total number of intervals for the generator. | ||
| * @throws IllegalArgumentException if the intervals is larger than {@link #MAX_INTERVALS} | ||
| */ | ||
| public RandomDiscreteTimestampGenerator(final long interval, final TimeUnit timeUnits, | ||
| final long startTimestamp, final int intervals) { | ||
| super(interval, timeUnits, startTimestamp); | ||
| this.intervals = intervals; | ||
| offsets = new Integer[intervals]; | ||
| setup(); | ||
| } | ||
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| /** | ||
| * Generates the offsets and shuffles the array. | ||
| */ | ||
| private void setup() { | ||
| if (intervals > MAX_INTERVALS) { | ||
| throw new IllegalArgumentException("Too many intervals for the in-memory " | ||
| + "array. The limit is " + MAX_INTERVALS + "."); | ||
| } | ||
| offsetIndex = 0; | ||
| for (int i = 0; i < intervals; i++) { | ||
| offsets[i] = i; | ||
| } | ||
| Utils.shuffleArray(offsets); | ||
| } | ||
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| @Override | ||
| public Long nextValue() { | ||
| if (offsetIndex >= offsets.length) { | ||
| throw new IllegalStateException("Reached the end of the random timestamp " | ||
| + "intervals: " + offsetIndex); | ||
| } | ||
| lastTimestamp = currentTimestamp; | ||
| currentTimestamp = startTimestamp + (offsets[offsetIndex++] * getOffset(1)); | ||
| return currentTimestamp; | ||
| } | ||
| } |
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core/src/test/java/com/yahoo/ycsb/generator/TestRandomDiscreteTimestampGenerator.java
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| /** | ||
| * Copyright (c) 2017 YCSB contributors. All rights reserved. | ||
| * <p> | ||
| * 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 | ||
| * <p> | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * <p> | ||
| * 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. See accompanying | ||
| * LICENSE file. | ||
| */ | ||
| package com.yahoo.ycsb.generator; | ||
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| import static org.testng.Assert.assertEquals; | ||
| import static org.testng.Assert.fail; | ||
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| import java.util.Collections; | ||
| import java.util.List; | ||
| import java.util.concurrent.TimeUnit; | ||
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| import org.testng.annotations.Test; | ||
| import org.testng.collections.Lists; | ||
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| public class TestRandomDiscreteTimestampGenerator { | ||
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| @Test | ||
| public void systemTime() throws Exception { | ||
| final RandomDiscreteTimestampGenerator generator = | ||
| new RandomDiscreteTimestampGenerator(60, TimeUnit.SECONDS, 60); | ||
| List<Long> generated = Lists.newArrayList(); | ||
| for (int i = 0; i < 60; i++) { | ||
| generated.add(generator.nextValue()); | ||
| } | ||
| assertEquals(generated.size(), 60); | ||
| try { | ||
| generator.nextValue(); | ||
| fail("Expected IllegalStateException"); | ||
| } catch (IllegalStateException e) { } | ||
| } | ||
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| @Test | ||
| public void withStartTime() throws Exception { | ||
| final RandomDiscreteTimestampGenerator generator = | ||
| new RandomDiscreteTimestampGenerator(60, TimeUnit.SECONDS, 1072915200L, 60); | ||
| List<Long> generated = Lists.newArrayList(); | ||
| for (int i = 0; i < 60; i++) { | ||
| generated.add(generator.nextValue()); | ||
| } | ||
| assertEquals(generated.size(), 60); | ||
| Collections.sort(generated); | ||
| long ts = 1072915200L - 60; // starts 1 interval in the past | ||
| for (final long t : generated) { | ||
| assertEquals(t, ts); | ||
| ts += 60; | ||
| } | ||
| try { | ||
| generator.nextValue(); | ||
| fail("Expected IllegalStateException"); | ||
| } catch (IllegalStateException e) { } | ||
| } | ||
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| @Test (expectedExceptions = IllegalArgumentException.class) | ||
| public void tooLarge() throws Exception { | ||
| new RandomDiscreteTimestampGenerator(60, TimeUnit.SECONDS, | ||
| RandomDiscreteTimestampGenerator.MAX_INTERVALS + 1); | ||
| } | ||
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| //TODO - With PowerMockito we could UT the initializeTimestamp(long) call. | ||
| // Otherwise it would involve creating more functions and that would get ugly. | ||
| } |