echauchot commented on code in PR #3: URL: https://github.com/apache/flink-connector-cassandra/pull/3#discussion_r1073557252
########## flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/SplitsGenerator.java: ########## @@ -0,0 +1,209 @@ +/* + * 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.connector.cassandra.source.split; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.math.BigInteger; +import java.util.ArrayList; +import java.util.Collections; +import java.util.HashSet; +import java.util.List; + +/** + * This class generates {@link CassandraSplit}s by generating {@link RingRange}s based on Cassandra + * cluster partitioner and Flink source parallelism. + */ +public final class SplitsGenerator { + private static final Logger LOG = LoggerFactory.getLogger(SplitsGenerator.class); + + private final String partitioner; + private final BigInteger rangeMin; + private final BigInteger rangeMax; + private final BigInteger rangeSize; + + public SplitsGenerator(String partitioner) { + this.partitioner = partitioner; + rangeMin = getRangeMin(); + rangeMax = getRangeMax(); + rangeSize = getRangeSize(); + } + + private BigInteger getRangeMin() { + if (partitioner.endsWith("RandomPartitioner")) { + return BigInteger.ZERO; + } else if (partitioner.endsWith("Murmur3Partitioner")) { + return BigInteger.valueOf(2).pow(63).negate(); + } else { + throw new UnsupportedOperationException( + "Unsupported partitioner. " + "Only Random and Murmur3 are supported"); + } + } + + private BigInteger getRangeMax() { + if (partitioner.endsWith("RandomPartitioner")) { + return BigInteger.valueOf(2).pow(127).subtract(BigInteger.ONE); + } else if (partitioner.endsWith("Murmur3Partitioner")) { + return BigInteger.valueOf(2).pow(63).subtract(BigInteger.ONE); + } else { + throw new UnsupportedOperationException( + "Unsupported partitioner. " + "Only Random and Murmur3 are supported"); + } + } + + private BigInteger getRangeSize() { + return rangeMax.subtract(rangeMin).add(BigInteger.ONE); + } + + /** + * Given properly ordered list of Cassandra tokens, compute at least {@code totalSplitCount} + * splits. Each split can contain several token ranges in order to reduce the overhead of + * Cassandra vnodes. Currently, token range grouping is not smart and doesn't check if they + * share the same replicas. + * + * @param totalSplitCount requested total amount of splits. This function may generate more + * splits. + * @param ringTokens list of all start tokens in Cassandra cluster. They have to be in ring + * order. + * @return list containing at least {@code totalSplitCount} CassandraSplits. + */ + public List<CassandraSplit> generateSplits(long totalSplitCount, List<BigInteger> ringTokens) { + if (totalSplitCount == 1) { + RingRange totalRingRange = RingRange.of(rangeMin, rangeMax); + return Collections.singletonList( + new CassandraSplit(Collections.singleton(totalRingRange))); + } + int tokenRangeCount = ringTokens.size(); + + List<RingRange> ringRanges = new ArrayList<>(); + for (int i = 0; i < tokenRangeCount; i++) { + BigInteger start = ringTokens.get(i); + BigInteger stop = ringTokens.get((i + 1) % tokenRangeCount); + + if (isNotInRange(start) || isNotInRange(stop)) { + throw new RuntimeException( + String.format( + "Tokens (%s,%s) not in range of %s", start, stop, partitioner)); + } + if (start.equals(stop) && tokenRangeCount != 1) { + throw new RuntimeException( + String.format( + "Tokens (%s,%s): two nodes have the same token", start, stop)); + } + + BigInteger rangeSize = stop.subtract(start); + if (rangeSize.compareTo(BigInteger.ZERO) <= 0) { + // wrap around case + rangeSize = rangeSize.add(this.rangeSize); + } + + // the below, in essence, does this: + // splitCount = Maths.ceil((rangeSize / cluster range size) * totalSplitCount) + BigInteger[] splitCountAndRemainder = + rangeSize + .multiply(BigInteger.valueOf(totalSplitCount)) + .divideAndRemainder(this.rangeSize); + + int splitCount = + splitCountAndRemainder[0].intValue() + + (splitCountAndRemainder[1].equals(BigInteger.ZERO) ? 0 : 1); + + LOG.debug("Dividing token range [{},{}) into {} splits", start, stop, splitCount); + + // Make BigInteger list of all the endpoints for the splits, including both start and + // stop + List<BigInteger> endpointTokens = new ArrayList<>(); + for (int j = 0; j <= splitCount; j++) { + BigInteger offset = + rangeSize + .multiply(BigInteger.valueOf(j)) + .divide(BigInteger.valueOf(splitCount)); + BigInteger token = start.add(offset); + if (token.compareTo(rangeMax) > 0) { + token = token.subtract(this.rangeSize); + } + // Long.MIN_VALUE is not a valid token and has to be silently incremented. + // See https://issues.apache.org/jira/browse/CASSANDRA-14684 + endpointTokens.add( + token.equals(BigInteger.valueOf(Long.MIN_VALUE)) + ? token.add(BigInteger.ONE) + : token); + } + + // Append the ringRanges between the endpoints + for (int j = 0; j < splitCount; j++) { + ringRanges.add(RingRange.of(endpointTokens.get(j), endpointTokens.get(j + 1))); + LOG.debug( + "Split #{}: [{},{})", + j + 1, + endpointTokens.get(j), + endpointTokens.get(j + 1)); + } + } + + BigInteger total = BigInteger.ZERO; + for (RingRange split : ringRanges) { + BigInteger size = split.span(rangeSize); + total = total.add(size); + } + if (!total.equals(rangeSize)) { + throw new RuntimeException( + "Some tokens are missing from the splits. This should not happen."); + } + return coalesceRingRanges(getTargetSplitSize(totalSplitCount), ringRanges); + } + + private boolean isNotInRange(BigInteger token) { + return token.compareTo(rangeMin) < 0 || token.compareTo(rangeMax) > 0; + } + + private List<CassandraSplit> coalesceRingRanges( + BigInteger targetSplitSize, List<RingRange> ringRanges) { + List<CassandraSplit> coalescedSplits = new ArrayList<>(); + List<RingRange> tokenRangesForCurrentSplit = new ArrayList<>(); + BigInteger tokenCount = BigInteger.ZERO; + + for (RingRange tokenRange : ringRanges) { + if (tokenRange.span(rangeSize).add(tokenCount).compareTo(targetSplitSize) > 0 + && !tokenRangesForCurrentSplit.isEmpty()) { + // enough tokens in that segment + LOG.debug( + "Got enough tokens for one split ({}) : {}", + tokenCount, + tokenRangesForCurrentSplit); + coalescedSplits.add(new CassandraSplit(new HashSet<>(tokenRangesForCurrentSplit))); + tokenRangesForCurrentSplit = new ArrayList<>(); + tokenCount = BigInteger.ZERO; + } + + tokenCount = tokenCount.add(tokenRange.span(rangeSize)); + tokenRangesForCurrentSplit.add(tokenRange); + } + + if (!tokenRangesForCurrentSplit.isEmpty()) { + coalescedSplits.add(new CassandraSplit(new HashSet<>(tokenRangesForCurrentSplit))); + } + return coalescedSplits; + } + + private BigInteger getTargetSplitSize(long splitCount) { + return rangeMax.subtract(rangeMin).divide(BigInteger.valueOf(splitCount)); Review Comment: See my general comments about Apache Beam Cassandra partitionner -- This is an automated message from the Apache Git Service. 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