MINOR Refactored the existing CheckpointFile in core module, moved to…

… server-common module and introduced it as SnapshotFile. (apache#11060)

MINOR Refactored the existing CheckpointFile in core module, moved to server-common module.

Refactored CheckpointFile to server-common module as a Java class and it is reused by LeaderCheckpointFile, OffsetCheckpointFile.
This will be used by CommittedOffsetsFile which checkpoints remote log metadata partitions with respective offsets in the default RemoteLogMetadataManager implementation.
Existing tests are available for LeaderCheckpointFile, OffsetCheckpointFile.

Reviewers: Jun Rao <junrao@gmail.com>

core/src/main/scala/kafka/server/checkpoints/CheckpointFileWithFailureHandler.scala

@@ -0,0 +1,56 @@
+/**
+  * 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 kafka.server.checkpoints
+
+import kafka.server.LogDirFailureChannel
+import org.apache.kafka.common.errors.KafkaStorageException
+import org.apache.kafka.server.common.CheckpointFile
+import CheckpointFile.EntryFormatter
+
+import java.io._
+import scala.collection.Seq
+import scala.jdk.CollectionConverters._
+
+class CheckpointFileWithFailureHandler[T](val file: File,
+                                          version: Int,
+                                          formatter: EntryFormatter[T],
+                                          logDirFailureChannel: LogDirFailureChannel,
+                                          logDir: String) {
+  private val checkpointFile = new CheckpointFile[T](file, version, formatter)
+
+  def write(entries: Iterable[T]): Unit = {
+      try {
+        checkpointFile.write(entries.toSeq.asJava)
+      } catch {
+        case e: IOException =>
+          val msg = s"Error while writing to checkpoint file ${file.getAbsolutePath}"
+          logDirFailureChannel.maybeAddOfflineLogDir(logDir, msg, e)
+          throw new KafkaStorageException(msg, e)
+      }
+  }
+
+  def read(): Seq[T] = {
+      try {
+        checkpointFile.read().asScala
+      } catch {
+        case e: IOException =>
+          val msg = s"Error while reading checkpoint file ${file.getAbsolutePath}"
+          logDirFailureChannel.maybeAddOfflineLogDir(logDir, msg, e)
+          throw new KafkaStorageException(msg, e)
+      }
+  }
+}

core/src/main/scala/kafka/server/checkpoints/LeaderEpochCheckpointFile.scala

@@ -16,12 +16,13 @@
  */
 package kafka.server.checkpoints
 
-import java.io._
-import java.util.regex.Pattern
-
 import kafka.server.LogDirFailureChannel
 import kafka.server.epoch.EpochEntry
+import org.apache.kafka.server.common.CheckpointFile.EntryFormatter
 
+import java.io._
+import java.util.Optional
+import java.util.regex.Pattern
 import scala.collection._
 
 trait LeaderEpochCheckpoint {
@@ -36,15 +37,15 @@ object LeaderEpochCheckpointFile {
 
   def newFile(dir: File): File = new File(dir, LeaderEpochCheckpointFilename)
 
-  object Formatter extends CheckpointFileFormatter[EpochEntry] {
+  object Formatter extends EntryFormatter[EpochEntry] {
 
-    override def toLine(entry: EpochEntry): String = s"${entry.epoch} ${entry.startOffset}"
+    override def toString(entry: EpochEntry): String = s"${entry.epoch} ${entry.startOffset}"
 
-    override def fromLine(line: String): Option[EpochEntry] = {
+    override def fromString(line: String): Optional[EpochEntry] = {
       WhiteSpacesPattern.split(line) match {
         case Array(epoch, offset) =>
-          Some(EpochEntry(epoch.toInt, offset.toLong))
-        case _ => None
+          Optional.of(EpochEntry(epoch.toInt, offset.toLong))
+        case _ => Optional.empty()
       }
     }
 
@@ -65,7 +66,7 @@ object LeaderEpochCheckpointFile {
 class LeaderEpochCheckpointFile(val file: File, logDirFailureChannel: LogDirFailureChannel = null) extends LeaderEpochCheckpoint {
   import LeaderEpochCheckpointFile._
 
-  val checkpoint = new CheckpointFile[EpochEntry](file, CurrentVersion, Formatter, logDirFailureChannel, file.getParentFile.getParent)
+  val checkpoint = new CheckpointFileWithFailureHandler[EpochEntry](file, CurrentVersion, Formatter, logDirFailureChannel, file.getParentFile.getParent)
 
   def write(epochs: Iterable[EpochEntry]): Unit = checkpoint.write(epochs)
 

core/src/main/scala/kafka/server/checkpoints/OffsetCheckpointFile.scala

@@ -16,29 +16,30 @@
   */
 package kafka.server.checkpoints
 
-import java.io._
-import java.util.regex.Pattern
-
 import kafka.server.LogDirFailureChannel
 import kafka.server.epoch.EpochEntry
 import org.apache.kafka.common.TopicPartition
+import org.apache.kafka.server.common.CheckpointFile.EntryFormatter
 
+import java.io._
+import java.util.Optional
+import java.util.regex.Pattern
 import scala.collection._
 
 object OffsetCheckpointFile {
   private val WhiteSpacesPattern = Pattern.compile("\\s+")
   private[checkpoints] val CurrentVersion = 0
 
-  object Formatter extends CheckpointFileFormatter[(TopicPartition, Long)] {
-    override def toLine(entry: (TopicPartition, Long)): String = {
+  object Formatter extends EntryFormatter[(TopicPartition, Long)] {
+    override def toString(entry: (TopicPartition, Long)): String = {
       s"${entry._1.topic} ${entry._1.partition} ${entry._2}"
     }
 
-    override def fromLine(line: String): Option[(TopicPartition, Long)] = {
+    override def fromString(line: String): Optional[(TopicPartition, Long)] = {
       WhiteSpacesPattern.split(line) match {
         case Array(topic, partition, offset) =>
-          Some(new TopicPartition(topic, partition.toInt), offset.toLong)
-        case _ => None
+          Optional.of(new TopicPartition(topic, partition.toInt), offset.toLong)
+        case _ => Optional.empty()
       }
     }
   }
@@ -61,7 +62,7 @@ trait OffsetCheckpoint {
  *  -----checkpoint file end----------
  */
 class OffsetCheckpointFile(val file: File, logDirFailureChannel: LogDirFailureChannel = null) {
-  val checkpoint = new CheckpointFile[(TopicPartition, Long)](file, OffsetCheckpointFile.CurrentVersion,
+  val checkpoint = new CheckpointFileWithFailureHandler[(TopicPartition, Long)](file, OffsetCheckpointFile.CurrentVersion,
     OffsetCheckpointFile.Formatter, logDirFailureChannel, file.getParent)
 
   def write(offsets: Map[TopicPartition, Long]): Unit = checkpoint.write(offsets)

core/src/test/scala/unit/kafka/server/checkpoints/LeaderEpochCheckpointFileTest.scala → core/src/test/scala/unit/kafka/server/checkpoints/LeaderEpochCheckpointFileWithFailureHandlerTest.scala

@@ -23,7 +23,7 @@ import kafka.utils.Logging
 import org.junit.jupiter.api.Assertions._
 import org.junit.jupiter.api.Test
 
-class LeaderEpochCheckpointFileTest extends Logging {
+class LeaderEpochCheckpointFileWithFailureHandlerTest extends Logging {
 
   @Test
   def shouldPersistAndOverwriteAndReloadFile(): Unit ={

core/src/test/scala/unit/kafka/server/checkpoints/OffsetCheckpointFileTest.scala → core/src/test/scala/unit/kafka/server/checkpoints/OffsetCheckpointFileWithFailureHandlerTest.scala

@@ -26,7 +26,7 @@ import org.mockito.Mockito
 
 import scala.collection.Map
 
-class OffsetCheckpointFileTest extends Logging {
+class OffsetCheckpointFileWithFailureHandlerTest extends Logging {
 
   @Test
   def shouldPersistAndOverwriteAndReloadFile(): Unit = {
@@ -93,7 +93,7 @@ class OffsetCheckpointFileTest extends Logging {
   def shouldThrowIfVersionIsNotRecognised(): Unit = {
     val file = TestUtils.tempFile()
     val logDirFailureChannel = new LogDirFailureChannel(10)
-    val checkpointFile = new CheckpointFile(file, OffsetCheckpointFile.CurrentVersion + 1,
+    val checkpointFile = new CheckpointFileWithFailureHandler(file, OffsetCheckpointFile.CurrentVersion + 1,
       OffsetCheckpointFile.Formatter, logDirFailureChannel, file.getParent)
     checkpointFile.write(Seq(new TopicPartition("foo", 5) -> 10L))
     assertThrows(classOf[KafkaStorageException], () => new OffsetCheckpointFile(checkpointFile.file, logDirFailureChannel).read())