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commit e03da5e053888512d85a40620bf52c300b233fc3 Author: Piotr Nowojski <[email protected]> AuthorDate: Fri Apr 4 15:28:14 2025 +0200 [FLINK-37399][runtime] Add SamplingWatermarkRingBuffer --- .../api/operators/source/WatermarkSampler.java | 66 +++++++++++++++ .../api/operators/source/WatermarkSamplerTest.java | 97 ++++++++++++++++++++++ 2 files changed, 163 insertions(+) diff --git a/flink-runtime/src/main/java/org/apache/flink/streaming/api/operators/source/WatermarkSampler.java b/flink-runtime/src/main/java/org/apache/flink/streaming/api/operators/source/WatermarkSampler.java new file mode 100644 index 00000000000..ae99e9cd97b --- /dev/null +++ b/flink-runtime/src/main/java/org/apache/flink/streaming/api/operators/source/WatermarkSampler.java @@ -0,0 +1,66 @@ +/* + * 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.flink.streaming.api.operators.source; + +import org.apache.flink.annotation.Internal; +import org.apache.flink.streaming.api.watermark.Watermark; + +import java.util.ArrayDeque; + +/** + * Allows to sample latest watermark values and store those samples in a ring buffer. Returns {@link + * Watermark.UNINITIALIZED} until fully initialized. + * + * <p>Special case for capacity = 0, then sampling is not used, and then always latest value is + * reported as oldest + */ +@Internal +public class WatermarkSampler { + private final ArrayDeque<Long> watermarksRingBuffer; + private final int capacity; + private long latestWatermark = Watermark.UNINITIALIZED.getTimestamp(); + + public WatermarkSampler(int capacity) { + this.capacity = capacity; + watermarksRingBuffer = new ArrayDeque<>(capacity); + for (int i = 0; i < capacity; i++) { + watermarksRingBuffer.add(Watermark.UNINITIALIZED.getTimestamp()); + } + } + + public void addLatest(long watermark) { + latestWatermark = watermark; + } + + public void sample() { + watermarksRingBuffer.add(latestWatermark); + watermarksRingBuffer.remove(); + } + + public long getLatest() { + return latestWatermark; + } + + public long getOldestSample() { + if (capacity == 0) { + return getLatest(); + } + return watermarksRingBuffer.getFirst(); + } +} diff --git a/flink-runtime/src/test/java/org/apache/flink/streaming/api/operators/source/WatermarkSamplerTest.java b/flink-runtime/src/test/java/org/apache/flink/streaming/api/operators/source/WatermarkSamplerTest.java new file mode 100644 index 00000000000..b67f54a404e --- /dev/null +++ b/flink-runtime/src/test/java/org/apache/flink/streaming/api/operators/source/WatermarkSamplerTest.java @@ -0,0 +1,97 @@ +/* + * 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.flink.streaming.api.operators.source; + +import org.apache.flink.streaming.api.watermark.Watermark; + +import org.junit.Test; + +import static org.assertj.core.api.Assertions.assertThat; + +/** Unit tests for the {@link WatermarkSampler}. */ +public class WatermarkSamplerTest { + + @Test + public void testCapacity0() { + WatermarkSampler ringBuffer = new WatermarkSampler(0); + + assertThat(ringBuffer.getOldestSample()).isEqualTo(Watermark.UNINITIALIZED.getTimestamp()); + assertThat(ringBuffer.getLatest()).isEqualTo(Watermark.UNINITIALIZED.getTimestamp()); + + ringBuffer.addLatest(13L); + assertThat(ringBuffer.getOldestSample()).isEqualTo(13L); + assertThat(ringBuffer.getLatest()).isEqualTo(13L); + ringBuffer.addLatest(42L); + ringBuffer.sample(); + assertThat(ringBuffer.getOldestSample()).isEqualTo(42L); + assertThat(ringBuffer.getLatest()).isEqualTo(42L); + } + + @Test + public void testCapacity2() { + WatermarkSampler ringBuffer = new WatermarkSampler(2); + + assertThat(ringBuffer.getOldestSample()).isEqualTo(Watermark.UNINITIALIZED.getTimestamp()); + assertThat(ringBuffer.getLatest()).isEqualTo(Watermark.UNINITIALIZED.getTimestamp()); + + ringBuffer.addLatest(13L); + ringBuffer.addLatest(42L); + ringBuffer.sample(); + assertThat(ringBuffer.getOldestSample()).isEqualTo(Watermark.UNINITIALIZED.getTimestamp()); + assertThat(ringBuffer.getLatest()).isEqualTo(42L); + + ringBuffer.addLatest(44L); + ringBuffer.sample(); + assertThat(ringBuffer.getOldestSample()).isEqualTo(42L); + assertThat(ringBuffer.getLatest()).isEqualTo(44L); + + ringBuffer.addLatest(1337L); + ringBuffer.sample(); + assertThat(ringBuffer.getOldestSample()).isEqualTo(44L); + assertThat(ringBuffer.getLatest()).isEqualTo(1337L); + } + + @Test + public void testCapacity3() { + WatermarkSampler ringBuffer = new WatermarkSampler(3); + + assertThat(ringBuffer.getOldestSample()).isEqualTo(Watermark.UNINITIALIZED.getTimestamp()); + assertThat(ringBuffer.getLatest()).isEqualTo(Watermark.UNINITIALIZED.getTimestamp()); + + ringBuffer.addLatest(42L); + ringBuffer.sample(); + assertThat(ringBuffer.getOldestSample()).isEqualTo(Watermark.UNINITIALIZED.getTimestamp()); + assertThat(ringBuffer.getLatest()).isEqualTo(42L); + + ringBuffer.addLatest(44L); + ringBuffer.sample(); + assertThat(ringBuffer.getOldestSample()).isEqualTo(Watermark.UNINITIALIZED.getTimestamp()); + assertThat(ringBuffer.getLatest()).isEqualTo(44L); + + ringBuffer.addLatest(1337L); + ringBuffer.sample(); + assertThat(ringBuffer.getOldestSample()).isEqualTo(42L); + assertThat(ringBuffer.getLatest()).isEqualTo(1337L); + + ringBuffer.addLatest(0L); + ringBuffer.sample(); + assertThat(ringBuffer.getOldestSample()).isEqualTo(44L); + assertThat(ringBuffer.getLatest()).isEqualTo(0L); + } +}
