nicktelford commented on code in PR #12393: URL: https://github.com/apache/kafka/pull/12393#discussion_r1003504997
########## streams/src/main/java/org/apache/kafka/streams/state/internals/AbstractTransactionalStore.java: ########## @@ -0,0 +1,442 @@ +/* + * 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.kafka.streams.state.internals; + +import static org.apache.kafka.streams.StreamsConfig.InternalConfig.IQ_CONSISTENCY_OFFSET_VECTOR_ENABLED; + +import java.io.File; +import java.io.IOException; +import java.util.Collection; +import java.util.Collections; +import java.util.HashSet; +import java.util.List; +import java.util.Map; +import java.util.NoSuchElementException; +import java.util.Set; +import java.util.stream.Collectors; +import org.apache.kafka.clients.consumer.ConsumerRecord; +import org.apache.kafka.common.serialization.Serializer; +import org.apache.kafka.common.utils.Bytes; +import org.apache.kafka.streams.KeyValue; +import org.apache.kafka.streams.StreamsConfig; +import org.apache.kafka.streams.processor.ProcessorContext; +import org.apache.kafka.streams.processor.StateStore; +import org.apache.kafka.streams.processor.StateStoreContext; +import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback; +import org.apache.kafka.streams.query.Position; +import org.apache.kafka.streams.query.PositionBound; +import org.apache.kafka.streams.query.Query; +import org.apache.kafka.streams.query.QueryConfig; +import org.apache.kafka.streams.query.QueryResult; +import org.apache.kafka.streams.state.KeyValueIterator; +import org.apache.kafka.streams.state.KeyValueStore; +import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder; + +public abstract class AbstractTransactionalStore<T extends KeyValueStore<Bytes, byte[]>> implements KeyValueStore<Bytes, byte[]> { + private static final byte MODIFICATION = 0x1; + private static final byte DELETION = 0x2; + private static final byte[] DELETION_VAL = {DELETION}; + + private StateStoreContext context; + + static final String PREFIX = "transactional-"; + //VisibleForTesting + public static final String TMP_SUFFIX = ".tmp"; + + private final Set<MergeKeyValueIterator> openIterators = Collections.synchronizedSet(new HashSet<>()); + + Map<String, Object> configs; + File stateDir; + + private boolean consistencyEnabled = false; + private Position position; + protected OffsetCheckpoint positionCheckpoint; + + KeyValueSegment createTmpStore(final String segmentName, + final String windowName, + final long segmentId, + final RocksDBMetricsRecorder metricsRecorder) { + return new KeyValueSegment(segmentName + TMP_SUFFIX, + windowName, + segmentId, + metricsRecorder); + } + + public abstract T mainStore(); + + public abstract KeyValueSegment tmpStore(); + + @Deprecated + @Override + public void init(final ProcessorContext context, final StateStore root) { + if (context instanceof StateStoreContext) { + init((StateStoreContext) context, root); + } else { + throw new UnsupportedOperationException( + "Use TransactionalKeyValueStore#init(StateStoreContext, StateStore) instead." + ); + } + } + + @Override + public void init(final StateStoreContext context, final StateStore root) { + this.context = context; + + doInit(context.appConfigs(), context.stateDir()); + ((RocksDBStore) mainStore()).openDB(configs, stateDir); + + final File positionCheckpointFile = new File(context.stateDir(), name() + ".position"); + this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile); + this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint); + tmpStore().consistencyEnabled = consistencyEnabled; + + // register and possibly restore the state from the logs + context.register( + root, + (RecordBatchingStateRestoreCallback) this::restoreBatch, + () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position) + ); + + consistencyEnabled = StreamsConfig.InternalConfig.getBoolean( + context.appConfigs(), + IQ_CONSISTENCY_OFFSET_VECTOR_ENABLED, + false); + } + + private void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) { + final Collection<ConsumerRecord<byte[], byte[]>> changelogRecords = records + .stream() + .map(record -> new ConsumerRecord<>( + record.topic(), + record.partition(), + record.offset(), + record.key(), + toUncommittedValue(record.value()))) + .collect(Collectors.toList()); + tmpStore().restoreBatch(changelogRecords); + commit(null); + } + + void doInit(final Map<String, Object> configs, final File stateDir) { + this.configs = configs; + this.stateDir = stateDir; + tmpStore().openDB(configs, stateDir); + } + + @Override + public synchronized void close() { + final HashSet<KeyValueIterator<Bytes, byte[]>> iterators; + synchronized (openIterators) { + iterators = new HashSet<>(openIterators); + } + for (final KeyValueIterator<Bytes, byte[]> iterator : iterators) { + iterator.close(); + } + + tmpStore().close(); + mainStore().close(); + } + + @Override + public void commit(final Long changelogOffset) { + tmpStore().commit(changelogOffset); + doCommit(); + } + + @Override + public boolean recover(final Long changelogOffset) { + truncateTmpStore(); + return true; + } + + private void truncateTmpStore() { + try { + tmpStore().close(); + tmpStore().destroy(); + tmpStore().openDB(configs, stateDir); + } catch (final IOException e) { + throw new RuntimeException(e); + } + } + + @Override + public boolean persistent() { + return mainStore().persistent(); + } + + @Override + public boolean isOpen() { + return tmpStore().isOpen() && mainStore().isOpen(); + } + + @Override + public void put(final Bytes key, final byte[] value) { + StoreQueryUtils.updatePosition(position, context); + tmpStore().put(key, toUncommittedValue(value)); + } + + @Override + public byte[] putIfAbsent(final Bytes key, final byte[] value) { + final byte[] prev = get(key); + if (prev == null) { + StoreQueryUtils.updatePosition(position, context); + tmpStore().put(key, toUncommittedValue(value)); + } + return prev; + } + + @Override + public void putAll(final List<KeyValue<Bytes, byte[]>> entries) { + StoreQueryUtils.updatePosition(position, context); + final List<KeyValue<Bytes, byte[]>> tmpEntries = entries + .stream() + .map(e -> new KeyValue<>(e.key, toUncommittedValue(e.value))) + .collect(Collectors.toList()); + tmpStore().putAll(tmpEntries); + } + + @Override + public byte[] delete(final Bytes key) { + final byte[] value = get(key); + tmpStore().put(key, DELETION_VAL); + return value; + } + + @Override + public byte[] get(final Bytes key) { + final byte[] tmpValue = tmpStore().get(key); + if (tmpValue == null) { + return mainStore().get(key); + } else if (tmpValue[0] == DELETION) { + return null; + } else { + return fromUncommittedValue(tmpValue); + } + } + + @Override + public KeyValueIterator<Bytes, byte[]> range(final Bytes from, final Bytes to) { + final MergeKeyValueIterator iterator = new MergeKeyValueIterator( + tmpStore().range(from, to), mainStore().range(from, to), openIterators); + openIterators.add(iterator); + return iterator; + } + + @Override + public KeyValueIterator<Bytes, byte[]> reverseRange(final Bytes from, final Bytes to) { + final MergeKeyValueIterator iterator = new MergeKeyValueIterator( + tmpStore().reverseRange(from, to), + mainStore().reverseRange(from, to), + true, + openIterators); + openIterators.add(iterator); + return iterator; + } + + @Override + public KeyValueIterator<Bytes, byte[]> all() { + final MergeKeyValueIterator iterator = new MergeKeyValueIterator( + tmpStore().all(), mainStore().all(), openIterators); + openIterators.add(iterator); + return iterator; + } + + @Override + public KeyValueIterator<Bytes, byte[]> reverseAll() { + final MergeKeyValueIterator iterator = new MergeKeyValueIterator( + tmpStore().reverseAll(), mainStore().reverseAll(), true, openIterators); + openIterators.add(iterator); + return iterator; + } + + @Override + public long approximateNumEntries() { + try { + return Math.addExact(tmpStore().approximateNumEntries(), mainStore().approximateNumEntries()); + } catch (final ArithmeticException e) { + return Long.MAX_VALUE; + } + } + + @Override + public Position getPosition() { + return position; + } + + private void doCommit() { + try (final KeyValueIterator<Bytes, byte[]> it = tmpStore().all()) { + while (it.hasNext()) { + final KeyValue<Bytes, byte[]> kv = it.next(); + mainStore().put(kv.key, fromUncommittedValue(kv.value)); + } + } + + truncateTmpStore(); + } + + @Override + public <R> QueryResult<R> query(final Query<R> query, final PositionBound positionBound, + final QueryConfig config) { + return StoreQueryUtils.handleBasicQueries( + query, + positionBound, + config, + this, + position, + context + ); + } + + @Override + public <PS extends Serializer<P>, P> KeyValueIterator<Bytes, byte[]> prefixScan(final P prefix, + final PS prefixKeySerializer) { + final MergeKeyValueIterator iterator = new MergeKeyValueIterator( + tmpStore().prefixScan(prefix, prefixKeySerializer), + mainStore().prefixScan(prefix, prefixKeySerializer), + openIterators); + openIterators.add(iterator); + return iterator; + } + + private static KeyValue<Bytes, byte[]> fromUncommittedKV(final KeyValue<Bytes, byte[]> kv) { + if (kv.value[0] == DELETION) { + return null; + } else { + final byte[] value = new byte[kv.value.length - 1]; + System.arraycopy(kv.value, 1, value, 0, value.length); + return new KeyValue<>(kv.key, value); + } + } + + private static byte[] fromUncommittedValue(final byte[] value) { Review Comment: Hmm, this is tricky. We could introduce a _third_ store, which stores uncommitted tombstones. For most use-cases, this store would be so lightweight that it could be in-memory. We could even use a heuristic to automatically choose the most appropriate type of store: - On startup, if an on-disk RocksDB tombstone store exists, use that. - Otherwise, use an in-memory store. - If the in-memory store exceeds a configurable threshold of keys, a RocksDB store is created to replace it, populated with the in-memory store keys. When querying, you'd query all 3 stores, using the tombstone store to omit results, provided the tombstones are newer than any values found in the other stores. I know it introduces _yet another store_, but I believe the majority of use-cases are so light on deletes that they'd comfortably fit in-memory, and therefore add very little overhead. -- This is an automated message from the Apache Git Service. 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