tkalkirill commented on code in PR #6601: URL: https://github.com/apache/ignite-3/pull/6601#discussion_r2355435440
########## modules/raft/src/main/java/org/apache/ignite/internal/raft/storage/segstore/IndexMemTable.java: ########## @@ -0,0 +1,140 @@ +/* + * 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.ignite.internal.raft.storage.segstore; + +import java.util.Arrays; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ConcurrentMap; +import java.util.concurrent.atomic.AtomicReferenceFieldUpdater; + +/** + * Mutable index memtable. + * + * <p>This class represents an in-memory index of the current segment file used by a {@link SegmentFileManager}. Index is + * essentially a mapping from {@code [groupId, logIndex]} to the offset in the segment file where the corresponding log entry is + * stored. + * + * <p>It is expected that entries for each {@code groupId} are written by one thread, therefore concurrent writes to the same + * {@code groupId} are not safe. However, reads from multiple threads are safe in relation to the aforementioned writes. + */ +class IndexMemTable { + private static class Stripe { Review Comment: Maybe move this class to a separate file? ########## modules/raft/src/main/java/org/apache/ignite/internal/raft/storage/segstore/IndexMemTable.java: ########## @@ -0,0 +1,140 @@ +/* + * 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.ignite.internal.raft.storage.segstore; + +import java.util.Arrays; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ConcurrentMap; +import java.util.concurrent.atomic.AtomicReferenceFieldUpdater; + +/** + * Mutable index memtable. + * + * <p>This class represents an in-memory index of the current segment file used by a {@link SegmentFileManager}. Index is + * essentially a mapping from {@code [groupId, logIndex]} to the offset in the segment file where the corresponding log entry is + * stored. + * + * <p>It is expected that entries for each {@code groupId} are written by one thread, therefore concurrent writes to the same + * {@code groupId} are not safe. However, reads from multiple threads are safe in relation to the aforementioned writes. + */ +class IndexMemTable { + private static class Stripe { + private final ConcurrentMap<Long, SegmentInfo> memTable = new ConcurrentHashMap<>(); + } + + private static class SegmentInfo { Review Comment: Maybe move this class to a separate file? ########## modules/raft/src/main/java/org/apache/ignite/internal/raft/storage/segstore/IndexMemTable.java: ########## @@ -0,0 +1,140 @@ +/* + * 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.ignite.internal.raft.storage.segstore; + +import java.util.Arrays; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ConcurrentMap; +import java.util.concurrent.atomic.AtomicReferenceFieldUpdater; + +/** + * Mutable index memtable. + * + * <p>This class represents an in-memory index of the current segment file used by a {@link SegmentFileManager}. Index is + * essentially a mapping from {@code [groupId, logIndex]} to the offset in the segment file where the corresponding log entry is + * stored. + * + * <p>It is expected that entries for each {@code groupId} are written by one thread, therefore concurrent writes to the same + * {@code groupId} are not safe. However, reads from multiple threads are safe in relation to the aforementioned writes. + */ +class IndexMemTable { + private static class Stripe { + private final ConcurrentMap<Long, SegmentInfo> memTable = new ConcurrentHashMap<>(); + } + + private static class SegmentInfo { + private static final AtomicReferenceFieldUpdater<SegmentInfo, int[]> SEGMENT_FILE_OFFSETS_UPDATER = + AtomicReferenceFieldUpdater.newUpdater(SegmentInfo.class, int[].class, "segmentFileOffsets"); + + private static final int INITIAL_SEGMENT_FILE_OFFSETS_CAPACITY = 10; + + /** + * Base log index. All log indexes in the memtable are relative to this value. + */ + private final long logIndexBase; + + /** + * Offsets in a segment file. + */ + private volatile int[] segmentFileOffsets = new int[INITIAL_SEGMENT_FILE_OFFSETS_CAPACITY]; + + /** + * Number of entries in the {@link #segmentFileOffsets} array. + * + * <p>Multi-threaded visibility is guaranteed by volatile reads or writes to the {@link #segmentFileOffsets} field. + */ + private int segmentFileOffsetSize = 0; + + SegmentInfo(long logIndexBase) { + this.logIndexBase = logIndexBase; + } + + void addOffset(long logIndex, int segmentFileOffset) { + int[] originalSegmentFileOffsets = this.segmentFileOffsets; + + int[] segmentFileOffsets = originalSegmentFileOffsets; + + // Check that log indexes are monotonically increasing. + assert segmentFileOffsetSize == logIndex - logIndexBase; + + if (segmentFileOffsets.length == segmentFileOffsetSize) { + segmentFileOffsets = Arrays.copyOf(segmentFileOffsets, segmentFileOffsets.length * 2); Review Comment: Do you think `IgniteIntList`/`IgniteIntList` would suit us? It probably does the same thing itself. ########## modules/raft/src/test/java/org/apache/ignite/internal/raft/storage/segstore/IndexMemTableTest.java: ########## @@ -0,0 +1,121 @@ +/* + * 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.ignite.internal.raft.storage.segstore; + +import static java.util.concurrent.CompletableFuture.allOf; +import static java.util.concurrent.CompletableFuture.runAsync; +import static org.apache.ignite.internal.testframework.matchers.CompletableFutureMatcher.willCompleteSuccessfully; +import static org.hamcrest.MatcherAssert.assertThat; +import static org.hamcrest.Matchers.either; +import static org.hamcrest.Matchers.is; + +import java.util.concurrent.BrokenBarrierException; +import java.util.concurrent.CompletableFuture; +import java.util.concurrent.CompletionException; +import java.util.concurrent.CyclicBarrier; +import java.util.concurrent.ExecutorService; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.TimeoutException; +import org.apache.ignite.internal.testframework.BaseIgniteAbstractTest; +import org.apache.ignite.internal.testframework.ExecutorServiceExtension; +import org.apache.ignite.internal.testframework.InjectExecutorService; +import org.junit.jupiter.api.Test; +import org.junit.jupiter.api.extension.ExtendWith; + +@ExtendWith(ExecutorServiceExtension.class) +class IndexMemTableTest extends BaseIgniteAbstractTest { + private static final int STRIPES = 10; + + private final IndexMemTable memTable = new IndexMemTable(STRIPES); + + @Test + void testPutGet() { + memTable.appendSegmentFileOffset(0, 0, 1); + memTable.appendSegmentFileOffset(0, 1, 2); + memTable.appendSegmentFileOffset(1, 0, 3); + memTable.appendSegmentFileOffset(1, 1, 4); + + assertThat(memTable.getSegmentFileOffset(0, 0), is(1)); + assertThat(memTable.getSegmentFileOffset(0, 1), is(2)); + assertThat(memTable.getSegmentFileOffset(1, 0), is(3)); + assertThat(memTable.getSegmentFileOffset(1, 1), is(4)); + } + + @Test + void testMissingValue() { + memTable.appendSegmentFileOffset(0, 5, 1); + + assertThat(memTable.getSegmentFileOffset(0, 1), is(0)); + assertThat(memTable.getSegmentFileOffset(0, 5), is(1)); + assertThat(memTable.getSegmentFileOffset(0, 6), is(0)); + } + + @Test + void testMultithreadedPutGet(@InjectExecutorService(threadCount = STRIPES * 2) ExecutorService executor) { Review Comment: Let's run this test, say, 10 times. ########## modules/raft/src/main/java/org/apache/ignite/internal/raft/storage/segstore/IndexMemTable.java: ########## @@ -0,0 +1,140 @@ +/* + * 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.ignite.internal.raft.storage.segstore; + +import java.util.Arrays; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ConcurrentMap; +import java.util.concurrent.atomic.AtomicReferenceFieldUpdater; + +/** + * Mutable index memtable. + * + * <p>This class represents an in-memory index of the current segment file used by a {@link SegmentFileManager}. Index is + * essentially a mapping from {@code [groupId, logIndex]} to the offset in the segment file where the corresponding log entry is + * stored. + * + * <p>It is expected that entries for each {@code groupId} are written by one thread, therefore concurrent writes to the same + * {@code groupId} are not safe. However, reads from multiple threads are safe in relation to the aforementioned writes. + */ +class IndexMemTable { + private static class Stripe { + private final ConcurrentMap<Long, SegmentInfo> memTable = new ConcurrentHashMap<>(); Review Comment: Please add in the description what the key and value are in this map. ########## modules/raft/src/main/java/org/apache/ignite/internal/raft/storage/segstore/IndexMemTable.java: ########## @@ -0,0 +1,140 @@ +/* + * 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.ignite.internal.raft.storage.segstore; + +import java.util.Arrays; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ConcurrentMap; +import java.util.concurrent.atomic.AtomicReferenceFieldUpdater; + +/** + * Mutable index memtable. + * + * <p>This class represents an in-memory index of the current segment file used by a {@link SegmentFileManager}. Index is + * essentially a mapping from {@code [groupId, logIndex]} to the offset in the segment file where the corresponding log entry is + * stored. + * + * <p>It is expected that entries for each {@code groupId} are written by one thread, therefore concurrent writes to the same + * {@code groupId} are not safe. However, reads from multiple threads are safe in relation to the aforementioned writes. + */ +class IndexMemTable { + private static class Stripe { + private final ConcurrentMap<Long, SegmentInfo> memTable = new ConcurrentHashMap<>(); + } + + private static class SegmentInfo { + private static final AtomicReferenceFieldUpdater<SegmentInfo, int[]> SEGMENT_FILE_OFFSETS_UPDATER = + AtomicReferenceFieldUpdater.newUpdater(SegmentInfo.class, int[].class, "segmentFileOffsets"); + + private static final int INITIAL_SEGMENT_FILE_OFFSETS_CAPACITY = 10; + + /** + * Base log index. All log indexes in the memtable are relative to this value. + */ + private final long logIndexBase; + + /** + * Offsets in a segment file. + */ + private volatile int[] segmentFileOffsets = new int[INITIAL_SEGMENT_FILE_OFFSETS_CAPACITY]; + + /** + * Number of entries in the {@link #segmentFileOffsets} array. + * + * <p>Multi-threaded visibility is guaranteed by volatile reads or writes to the {@link #segmentFileOffsets} field. + */ + private int segmentFileOffsetSize = 0; + + SegmentInfo(long logIndexBase) { + this.logIndexBase = logIndexBase; + } + + void addOffset(long logIndex, int segmentFileOffset) { + int[] originalSegmentFileOffsets = this.segmentFileOffsets; + + int[] segmentFileOffsets = originalSegmentFileOffsets; + + // Check that log indexes are monotonically increasing. + assert segmentFileOffsetSize == logIndex - logIndexBase; Review Comment: Please add error message. ########## modules/raft/src/main/java/org/apache/ignite/internal/raft/storage/segstore/IndexMemTable.java: ########## @@ -0,0 +1,140 @@ +/* + * 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.ignite.internal.raft.storage.segstore; + +import java.util.Arrays; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ConcurrentMap; +import java.util.concurrent.atomic.AtomicReferenceFieldUpdater; + +/** + * Mutable index memtable. + * + * <p>This class represents an in-memory index of the current segment file used by a {@link SegmentFileManager}. Index is + * essentially a mapping from {@code [groupId, logIndex]} to the offset in the segment file where the corresponding log entry is + * stored. + * + * <p>It is expected that entries for each {@code groupId} are written by one thread, therefore concurrent writes to the same + * {@code groupId} are not safe. However, reads from multiple threads are safe in relation to the aforementioned writes. + */ +class IndexMemTable { + private static class Stripe { + private final ConcurrentMap<Long, SegmentInfo> memTable = new ConcurrentHashMap<>(); + } + + private static class SegmentInfo { + private static final AtomicReferenceFieldUpdater<SegmentInfo, int[]> SEGMENT_FILE_OFFSETS_UPDATER = + AtomicReferenceFieldUpdater.newUpdater(SegmentInfo.class, int[].class, "segmentFileOffsets"); + + private static final int INITIAL_SEGMENT_FILE_OFFSETS_CAPACITY = 10; + + /** + * Base log index. All log indexes in the memtable are relative to this value. Review Comment: I don't understand what this means. From the ticket description, it should be the initial/start offset of all indexes for the group? ########## modules/raft/src/test/java/org/apache/ignite/internal/raft/storage/segstore/IndexMemTableTest.java: ########## @@ -0,0 +1,121 @@ +/* + * 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.ignite.internal.raft.storage.segstore; + +import static java.util.concurrent.CompletableFuture.allOf; +import static java.util.concurrent.CompletableFuture.runAsync; +import static org.apache.ignite.internal.testframework.matchers.CompletableFutureMatcher.willCompleteSuccessfully; +import static org.hamcrest.MatcherAssert.assertThat; +import static org.hamcrest.Matchers.either; +import static org.hamcrest.Matchers.is; + +import java.util.concurrent.BrokenBarrierException; +import java.util.concurrent.CompletableFuture; +import java.util.concurrent.CompletionException; +import java.util.concurrent.CyclicBarrier; +import java.util.concurrent.ExecutorService; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.TimeoutException; +import org.apache.ignite.internal.testframework.BaseIgniteAbstractTest; +import org.apache.ignite.internal.testframework.ExecutorServiceExtension; +import org.apache.ignite.internal.testframework.InjectExecutorService; +import org.junit.jupiter.api.Test; +import org.junit.jupiter.api.extension.ExtendWith; + +@ExtendWith(ExecutorServiceExtension.class) +class IndexMemTableTest extends BaseIgniteAbstractTest { + private static final int STRIPES = 10; + + private final IndexMemTable memTable = new IndexMemTable(STRIPES); + + @Test + void testPutGet() { + memTable.appendSegmentFileOffset(0, 0, 1); + memTable.appendSegmentFileOffset(0, 1, 2); + memTable.appendSegmentFileOffset(1, 0, 3); + memTable.appendSegmentFileOffset(1, 1, 4); + + assertThat(memTable.getSegmentFileOffset(0, 0), is(1)); + assertThat(memTable.getSegmentFileOffset(0, 1), is(2)); + assertThat(memTable.getSegmentFileOffset(1, 0), is(3)); + assertThat(memTable.getSegmentFileOffset(1, 1), is(4)); + } + + @Test + void testMissingValue() { + memTable.appendSegmentFileOffset(0, 5, 1); + + assertThat(memTable.getSegmentFileOffset(0, 1), is(0)); + assertThat(memTable.getSegmentFileOffset(0, 5), is(1)); + assertThat(memTable.getSegmentFileOffset(0, 6), is(0)); + } + + @Test + void testMultithreadedPutGet(@InjectExecutorService(threadCount = STRIPES * 2) ExecutorService executor) { Review Comment: I suggest adding a test with one writer and two readers and checking that they will work correctly to try to find races. ########## modules/raft/src/main/java/org/apache/ignite/internal/raft/storage/segstore/IndexMemTable.java: ########## @@ -0,0 +1,140 @@ +/* + * 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.ignite.internal.raft.storage.segstore; + +import java.util.Arrays; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ConcurrentMap; +import java.util.concurrent.atomic.AtomicReferenceFieldUpdater; + +/** + * Mutable index memtable. + * + * <p>This class represents an in-memory index of the current segment file used by a {@link SegmentFileManager}. Index is + * essentially a mapping from {@code [groupId, logIndex]} to the offset in the segment file where the corresponding log entry is + * stored. + * + * <p>It is expected that entries for each {@code groupId} are written by one thread, therefore concurrent writes to the same + * {@code groupId} are not safe. However, reads from multiple threads are safe in relation to the aforementioned writes. + */ +class IndexMemTable { + private static class Stripe { + private final ConcurrentMap<Long, SegmentInfo> memTable = new ConcurrentHashMap<>(); + } + + private static class SegmentInfo { + private static final AtomicReferenceFieldUpdater<SegmentInfo, int[]> SEGMENT_FILE_OFFSETS_UPDATER = + AtomicReferenceFieldUpdater.newUpdater(SegmentInfo.class, int[].class, "segmentFileOffsets"); + + private static final int INITIAL_SEGMENT_FILE_OFFSETS_CAPACITY = 10; + + /** + * Base log index. All log indexes in the memtable are relative to this value. + */ + private final long logIndexBase; + + /** + * Offsets in a segment file. + */ + private volatile int[] segmentFileOffsets = new int[INITIAL_SEGMENT_FILE_OFFSETS_CAPACITY]; + + /** + * Number of entries in the {@link #segmentFileOffsets} array. + * + * <p>Multi-threaded visibility is guaranteed by volatile reads or writes to the {@link #segmentFileOffsets} field. + */ + private int segmentFileOffsetSize = 0; + + SegmentInfo(long logIndexBase) { + this.logIndexBase = logIndexBase; + } + + void addOffset(long logIndex, int segmentFileOffset) { + int[] originalSegmentFileOffsets = this.segmentFileOffsets; + + int[] segmentFileOffsets = originalSegmentFileOffsets; + + // Check that log indexes are monotonically increasing. + assert segmentFileOffsetSize == logIndex - logIndexBase; + + if (segmentFileOffsets.length == segmentFileOffsetSize) { + segmentFileOffsets = Arrays.copyOf(segmentFileOffsets, segmentFileOffsets.length * 2); + } + + segmentFileOffsets[segmentFileOffsetSize++] = segmentFileOffset; + + // Simple assignment would suffice, since we only have one thread writing to this field, but we use compareAndSet to verify + // this invariant, just in case. + boolean updated = SEGMENT_FILE_OFFSETS_UPDATER.compareAndSet(this, originalSegmentFileOffsets, segmentFileOffsets); + + assert updated : "Concurrent writes detected"; + } + + int getOffset(long logIndex) { + long offsetIndex = logIndex - logIndexBase; + + if (offsetIndex < 0) { + return 0; + } + + // Read segmentFileOffsets first to acquire segmentFileOffsetSize. + int[] segmentFileOffsets = this.segmentFileOffsets; + + if (offsetIndex >= segmentFileOffsetSize) { + return 0; + } + + return segmentFileOffsets[(int) offsetIndex]; + } + } + + private final Stripe[] stripes; + + IndexMemTable(int stripes) { + this.stripes = new Stripe[stripes]; + + for (int i = 0; i < stripes; i++) { + this.stripes[i] = new Stripe(); + } + } + + void appendSegmentFileOffset(long groupId, long logIndex, int segmentFileOffset) { + // File offset can be less than 0 (it's treated as an unsigned integer) but never 0, because of the file header. + assert segmentFileOffset != 0 : "Segment file offset must not be 0"; Review Comment: please add `groupId` to error message. ########## modules/raft/src/main/java/org/apache/ignite/internal/raft/storage/segstore/IndexMemTable.java: ########## @@ -0,0 +1,140 @@ +/* + * 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.ignite.internal.raft.storage.segstore; + +import java.util.Arrays; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ConcurrentMap; +import java.util.concurrent.atomic.AtomicReferenceFieldUpdater; + +/** + * Mutable index memtable. + * + * <p>This class represents an in-memory index of the current segment file used by a {@link SegmentFileManager}. Index is + * essentially a mapping from {@code [groupId, logIndex]} to the offset in the segment file where the corresponding log entry is + * stored. + * + * <p>It is expected that entries for each {@code groupId} are written by one thread, therefore concurrent writes to the same + * {@code groupId} are not safe. However, reads from multiple threads are safe in relation to the aforementioned writes. + */ +class IndexMemTable { + private static class Stripe { + private final ConcurrentMap<Long, SegmentInfo> memTable = new ConcurrentHashMap<>(); + } + + private static class SegmentInfo { + private static final AtomicReferenceFieldUpdater<SegmentInfo, int[]> SEGMENT_FILE_OFFSETS_UPDATER = Review Comment: Maybe use the younger `VarHandle`? ########## modules/raft/src/main/java/org/apache/ignite/internal/raft/storage/segstore/SegmentPayload.java: ########## @@ -0,0 +1,73 @@ +/* + * 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.ignite.internal.raft.storage.segstore; + +import java.nio.ByteBuffer; +import org.apache.ignite.internal.util.FastCrc; +import org.apache.ignite.raft.jraft.entity.LogEntry; +import org.apache.ignite.raft.jraft.entity.codec.LogEntryEncoder; + +/** + * Describes a payload entry in a segment file. + * + * @see SegmentFileManager + */ +class SegmentPayload { Review Comment: Perhaps the description of the payload should be inserted here? -- This is an automated message from the Apache Git Service. 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