[GitHub] [kafka] ijuma commented on a diff in pull request #13010: KAFKA-14475: Move TimeIndex/LazyIndex to storage module

[GitBox <gi...@apache.org>]

ijuma commented on code in PR #13010:
URL: https://github.com/apache/kafka/pull/13010#discussion_r1053853496


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storage/src/main/java/org/apache/kafka/server/log/internals/TimeIndex.java:
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@@ -0,0 +1,290 @@
+/*
+ * 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.server.log.internals;
+
+import org.apache.kafka.common.errors.InvalidOffsetException;
+import org.apache.kafka.common.record.RecordBatch;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.MappedByteBuffer;
+
+/**
+ * An index that maps from the timestamp to the logical offsets of the messages in a segment. This index might be
+ * sparse, i.e. it may not hold an entry for all the messages in the segment.
+ *
+ * The index is stored in a file that is preallocated to hold a fixed maximum amount of 12-byte time index entries.
+ * The file format is a series of time index entries. The physical format is a 8 bytes timestamp and a 4 bytes "relative"
+ * offset used in the [[OffsetIndex]]. A time index entry (TIMESTAMP, OFFSET) means that the biggest timestamp seen
+ * before OFFSET is TIMESTAMP. i.e. Any message whose timestamp is greater than TIMESTAMP must come after OFFSET.
+ *
+ * All external APIs translate from relative offsets to full offsets, so users of this class do not interact with the internal
+ * storage format.
+ *
+ * The timestamps in the same time index file are guaranteed to be monotonically increasing.
+ *
+ * The index supports timestamp lookup for a memory map of this file. The lookup is done using a binary search to find
+ * the offset of the message whose indexed timestamp is closest but smaller or equals to the target timestamp.
+ *
+ * Time index files can be opened in two ways: either as an empty, mutable index that allows appending or
+ * an immutable read-only index file that has previously been populated. The makeReadOnly method will turn a mutable file into an
+ * immutable one and truncate off any extra bytes. This is done when the index file is rolled over.
+ *
+ * No attempt is made to checksum the contents of this file, in the event of a crash it is rebuilt.
+ *
+ */
+public class TimeIndex extends AbstractIndex {
+    private static final Logger log = LoggerFactory.getLogger(TimeIndex.class);
+    private static final int ENTRY_SIZE = 12;
+
+    private volatile TimestampOffset lastEntry;
+
+    public TimeIndex(File file, long baseOffset) throws IOException {

Review Comment:
   Good catch, I think I changed some callers not to rely on this anymore, so we can remove it. Pushed the fix.



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