jt2594838 commented on code in PR #16886:
URL: https://github.com/apache/iotdb/pull/16886#discussion_r2601785627
##########
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/DataRegion.java:
##########
@@ -369,6 +370,9 @@ public class DataRegion implements IDataRegionForQuery {
private ILoadDiskSelector ordinaryLoadDiskSelector;
private ILoadDiskSelector pipeAndIoTV2LoadDiskSelector;
+ /** Delay analyzer for tracking data arrival delays and calculating safe
watermarks */
+ private final DelayAnalyzer delayAnalyzer;
+
Review Comment:
Add a switch for this to avoid affecting performance of existing scenarios.
##########
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/tools/DelayAnalyzer.java:
##########
@@ -0,0 +1,346 @@
+/*
+ * 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.iotdb.db.tools;
+
+import org.apache.iotdb.commons.utils.TestOnly;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Arrays;
+import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+
+/**
+ * DelayAnalyzer: Calculate watermarks for in-order and out-of-order data
based on statistics and
+ * models
+ *
+ * <p>This implementation is based on the paper "Separation or Not: On
Handling Out-of-Order
+ * Time-Series Data" (ICDE 2022) proposed method, which dynamically calculates
safe watermarks by
+ * analyzing the Cumulative Distribution Function (CDF) of data arrival delays.
+ *
+ * <p>Core concepts:
+ *
+ * <ul>
+ * <li>Record the generation time (Event Time) and arrival time (System
Time) of each data point
+ * <li>Calculate delay: delay = arrivalTime - generationTime
+ * <li>Maintain a sliding window to store recent delay samples
+ * <li>Use CDF to calculate delay quantiles (e.g., P99) at specific
confidence levels
+ * <li>Safe watermark = Current system time - P99 delay
+ * </ul>
+ *
+ * <p>Key formulas from the paper:
+ *
+ * <ul>
+ * <li>Delay calculation: p.t_d = p.t_a - p.t_g (Formula 160)
+ * <li>Use F(x) (CDF) to estimate the probability of out-of-order data
(Reference 110)
+ * <li>Dynamic delay distribution: Use sliding window to maintain recent
delay samples
+ * </ul>
+ *
+ * <p>Features:
+ *
+ * <ul>
+ * <li>Thread-safe: Uses ReadWriteLock to support high-concurrency
read/write operations
+ * <li>Memory efficient: Uses circular buffer with fixed memory footprint
+ * <li>Clock skew handling: Automatically handles negative delays (clock
rollback)
+ * <li>Dynamic adaptation: Sliding window automatically adapts to changes in
delay distribution
+ * </ul>
+ *
+ * @see <a href="https://ieeexplore.ieee.org/document/9835234";>ICDE 2022
Paper</a>
+ */
+public class DelayAnalyzer {
+
+ private static final Logger LOGGER =
LoggerFactory.getLogger(DelayAnalyzer.class);
+
+ /** Default window size, empirical value: 10000 sample points */
+ public static final int DEFAULT_WINDOW_SIZE = 10000;
+
+ /** Recommended window size range */
+ public static final int MIN_WINDOW_SIZE = 1000;
+
+ public static final int MAX_WINDOW_SIZE = 100000;
+
+ /** Default confidence level: 99% */
+ public static final double DEFAULT_CONFIDENCE_LEVEL = 0.99;
+
+ /**
+ * Sliding window size for storing recent delay sample points. A larger
window provides more
+ * accurate P99 calculations but increases memory and sorting overhead. The
paper mentions using
+ * dynamic delay distribution to adapt to changes in delay patterns.
+ */
+ private final int windowSize;
+
+ /** Circular buffer storing delay samples (unit: milliseconds) */
+ private final long[] delaySamples;
+
+ /** Current write position (cursor of the circular buffer) */
+ private int cursor = 0;
+
+ /** Flag indicating whether the buffer is full */
+ private boolean isFull = false;
+
+ /** Total number of samples (for statistics) */
+ private long totalSamples = 0;
+
+ /**
+ * ReadWriteLock ensures thread safety in high-concurrency scenarios. Read
operations (calculating
+ * quantiles) use read lock, write operations (updating delays) use write
lock.
+ */
+ private final ReadWriteLock lock = new ReentrantReadWriteLock();
+
+ /** Constructor using default window size */
+ public DelayAnalyzer() {
+ this(DEFAULT_WINDOW_SIZE);
+ }
+
+ /**
+ * Constructor
+ *
+ * @param windowSize Sliding window size, recommended range: 5000 - 10000.
Larger windows provide
+ * more accurate statistics but increase memory and computational
overhead.
+ * @throws IllegalArgumentException if window size is not within valid range
+ */
+ public DelayAnalyzer(int windowSize) {
+ if (windowSize < MIN_WINDOW_SIZE || windowSize > MAX_WINDOW_SIZE) {
+ throw new IllegalArgumentException(
+ String.format(
+ "Window size must be between %d and %d, got %d",
+ MIN_WINDOW_SIZE, MAX_WINDOW_SIZE, windowSize));
+ }
+ this.windowSize = windowSize;
+ this.delaySamples = new long[windowSize];
+ }
+
+ @TestOnly
+ public DelayAnalyzer(int windowSize, int placeHolder) {
+ this.windowSize = windowSize;
+ this.delaySamples = new long[windowSize];
+ }
Review Comment:
May use a static method instead of adding a hard-to-understand placeHolder
##########
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/tools/DelayAnalyzer.java:
##########
@@ -0,0 +1,346 @@
+/*
+ * 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.iotdb.db.tools;
+
+import org.apache.iotdb.commons.utils.TestOnly;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Arrays;
+import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+
+/**
+ * DelayAnalyzer: Calculate watermarks for in-order and out-of-order data
based on statistics and
+ * models
+ *
+ * <p>This implementation is based on the paper "Separation or Not: On
Handling Out-of-Order
+ * Time-Series Data" (ICDE 2022) proposed method, which dynamically calculates
safe watermarks by
+ * analyzing the Cumulative Distribution Function (CDF) of data arrival delays.
+ *
+ * <p>Core concepts:
+ *
+ * <ul>
+ * <li>Record the generation time (Event Time) and arrival time (System
Time) of each data point
+ * <li>Calculate delay: delay = arrivalTime - generationTime
+ * <li>Maintain a sliding window to store recent delay samples
+ * <li>Use CDF to calculate delay quantiles (e.g., P99) at specific
confidence levels
+ * <li>Safe watermark = Current system time - P99 delay
+ * </ul>
+ *
+ * <p>Key formulas from the paper:
+ *
+ * <ul>
+ * <li>Delay calculation: p.t_d = p.t_a - p.t_g (Formula 160)
+ * <li>Use F(x) (CDF) to estimate the probability of out-of-order data
(Reference 110)
+ * <li>Dynamic delay distribution: Use sliding window to maintain recent
delay samples
+ * </ul>
+ *
+ * <p>Features:
+ *
+ * <ul>
+ * <li>Thread-safe: Uses ReadWriteLock to support high-concurrency
read/write operations
+ * <li>Memory efficient: Uses circular buffer with fixed memory footprint
+ * <li>Clock skew handling: Automatically handles negative delays (clock
rollback)
+ * <li>Dynamic adaptation: Sliding window automatically adapts to changes in
delay distribution
+ * </ul>
+ *
+ * @see <a href="https://ieeexplore.ieee.org/document/9835234";>ICDE 2022
Paper</a>
+ */
+public class DelayAnalyzer {
+
+ private static final Logger LOGGER =
LoggerFactory.getLogger(DelayAnalyzer.class);
+
+ /** Default window size, empirical value: 10000 sample points */
+ public static final int DEFAULT_WINDOW_SIZE = 10000;
+
+ /** Recommended window size range */
+ public static final int MIN_WINDOW_SIZE = 1000;
+
+ public static final int MAX_WINDOW_SIZE = 100000;
+
+ /** Default confidence level: 99% */
+ public static final double DEFAULT_CONFIDENCE_LEVEL = 0.99;
Review Comment:
better to add as some configurations.
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