lukecwik commented on a change in pull request #11715: URL: https://github.com/apache/beam/pull/11715#discussion_r428304723
########## File path: sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/splittabledofn/GrowableOffsetRangeTracker.java ########## @@ -0,0 +1,143 @@ +/* + * 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.beam.sdk.transforms.splittabledofn; + +import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkNotNull; + +import java.math.BigDecimal; +import java.math.MathContext; +import org.apache.beam.sdk.annotations.Experimental; +import org.apache.beam.sdk.annotations.Experimental.Kind; +import org.apache.beam.sdk.io.range.OffsetRange; +import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Suppliers; + +/** + * An {@link OffsetRangeTracker} for tracking a growable offset range. {@code Long.MAX_VALUE} is + * used as the end of the range to indicate infinity. + * + * <p>An offset range is considered growable when the end offset could grow (or change) during + * execution time (e.g., Kafka topic partition offset, appended file, ...). + * + * <p>The growable range is marked as done by claiming {@code Long.MAX_VALUE}. + */ +@Experimental(Kind.SPLITTABLE_DO_FN) +public class GrowableOffsetRangeTracker extends OffsetRangeTracker { + /** + * Provides the estimated end offset of the range. + * + * <p>{@link #estimate} is called to give the end offset when {@link #trySplit} or {@link + * #getProgress} is invoked. The end offset is exclusive for the range. The estimated end is not + * required to monotonically increase as it will only be taken into consideration when the + * estimated end offset is larger than the current position. Returning {@code Long.MAX_VALUE} as + * the estimate implies the largest possible position for the range is {@code Long.MAX_VALUE - 1}. + * Return {@code Long.MIN_VALUE} if an estimate can not be provided. + * + * <p>Providing a good estimate is important for an accurate progress signal and will impact + * splitting decisions by the runner. + * + * <p>If {@link #estimate} is expensive to compute, consider wrapping the implementation with + * {@link Suppliers#memoizeWithExpiration} or equivalent as an optimization. + * + * <p>TODO(BEAM-10032): Also consider using {@link RangeEndEstimator} when the range is not ended + * with {@code Long.MAX_VALUE}. + */ + @FunctionalInterface + public interface RangeEndEstimator { + long estimate(); + } + + private final RangeEndEstimator rangeEndEstimator; + + public GrowableOffsetRangeTracker(long start, RangeEndEstimator rangeEndEstimator) { + super(new OffsetRange(start, Long.MAX_VALUE)); + this.rangeEndEstimator = checkNotNull(rangeEndEstimator); + } + + @Override + public SplitResult<OffsetRange> trySplit(double fractionOfRemainder) { + // If current tracking range is no longer growable, split it as a normal range. + if (range.getTo() != Long.MAX_VALUE || range.getTo() == range.getFrom()) { + return super.trySplit(fractionOfRemainder); + } + // If current range has been done, there is no more space to split. + if (lastAttemptedOffset != null && lastAttemptedOffset == Long.MAX_VALUE) { + return null; + } + BigDecimal cur = + (lastAttemptedOffset == null) + ? BigDecimal.valueOf(range.getFrom()).subtract(BigDecimal.ONE, MathContext.DECIMAL128) + : BigDecimal.valueOf(lastAttemptedOffset); + + // Fetch the estimated end offset. If the estimated end is smaller than the next offset, use + // the next offset as end. + BigDecimal estimateRangeEnd = + BigDecimal.valueOf(rangeEndEstimator.estimate()) + .max(cur.add(BigDecimal.ONE, MathContext.DECIMAL128)); + + // Convert to BigDecimal in computation to prevent overflow, which may result in loss of + // precision. + // split = cur + max(1, (estimateRangeEnd - cur) * fractionOfRemainder) + BigDecimal splitPos = + cur.add( + estimateRangeEnd + .subtract(cur, MathContext.DECIMAL128) + .multiply(BigDecimal.valueOf(fractionOfRemainder), MathContext.DECIMAL128) + .max(BigDecimal.ONE), + MathContext.DECIMAL128); + long split = splitPos.longValue(); + if (split > estimateRangeEnd.longValue()) { + return null; + } + OffsetRange res = new OffsetRange(split, range.getTo()); + this.range = new OffsetRange(range.getFrom(), split); + return SplitResult.of(range, res); + } + + @Override + public Progress getProgress() { + // If current tracking range is no longer growable, get progress as a normal range. + if (range.getTo() != Long.MAX_VALUE || range.getTo() == range.getFrom()) { + return super.getProgress(); + } + + // Convert to BigDecimal in computation to prevent overflow, which may result in lost of + // precision. + BigDecimal estimateRangeEnd = BigDecimal.valueOf(rangeEndEstimator.estimate()); + + if (lastAttemptedOffset == null) { + return Progress.from( + 0, + estimateRangeEnd + .subtract(BigDecimal.valueOf(range.getFrom()), MathContext.DECIMAL128) + .max(BigDecimal.ZERO) + .doubleValue()); + } + + BigDecimal workRemaining = + estimateRangeEnd + .subtract(BigDecimal.valueOf(lastAttemptedOffset), MathContext.DECIMAL128) + .max(BigDecimal.ZERO); + BigDecimal totalWork = + estimateRangeEnd + .max(BigDecimal.valueOf(lastAttemptedOffset)) + .subtract(BigDecimal.valueOf(range.getFrom())); Review comment: Doesn't this subtract need the DECIMAL128 math context? ########## File path: sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/splittabledofn/OffsetRangeTracker.java ########## @@ -120,13 +136,27 @@ public String toString() { public Progress getProgress() { // If we have never attempted an offset, we return the length of the entire range as work // remaining. + // Convert to BigDecimal in computation to prevent overflow, which may result in loss of + // precision. if (lastAttemptedOffset == null) { - return Progress.from(0, range.getTo() - range.getFrom()); + return Progress.from( + 0, + BigDecimal.valueOf(range.getTo()) + .subtract(BigDecimal.valueOf(range.getFrom()), MathContext.DECIMAL128) + .doubleValue()); } // Compute the amount of work remaining from where we are to where we are attempting to get to // with a minimum of zero in case we have claimed beyond the end of the range. - long workRemaining = Math.max(range.getTo() - lastAttemptedOffset, 0); - return Progress.from(range.getTo() - range.getFrom() - workRemaining, workRemaining); + BigDecimal workRemaining = + BigDecimal.valueOf(range.getTo()) + .subtract(BigDecimal.valueOf(lastAttemptedOffset), MathContext.DECIMAL128) + .max(BigDecimal.ZERO); + BigDecimal wholeWork = Review comment: nit: `wholeWork` -> `totalWork` ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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