[GitHub] [kafka] junrao commented on a change in pull request #10041: MINOR: Prevent creating partition.metadata until ID can be written

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

junrao commented on a change in pull request #10041:
URL: https://github.com/apache/kafka/pull/10041#discussion_r572399914



##########
File path: core/src/main/scala/kafka/log/Log.scala
##########
@@ -341,10 +342,15 @@ class Log(@volatile private var _dir: File,
     producerStateManager.removeStraySnapshots(segments.values().asScala.map(_.baseOffset).toSeq)
     loadProducerState(logEndOffset, reloadFromCleanShutdown = hadCleanShutdown)
 
-    // Recover topic ID if present
+    // Delete partition metadata file if the version does not support topic IDs.
+    // Recover topic ID if present and topic IDs are supported
     partitionMetadataFile.foreach { file =>
-      if (!file.isEmpty())
-        topicId = file.read().topicId
+      if (file.exists()) {
+        if (!usesTopicId)
+          file.delete()

Review comment:
       Does partitionMetadataFile need to be of Some? It seems that we can just always instantiate the object.

##########
File path: core/src/main/scala/kafka/log/Log.scala
##########
@@ -256,7 +256,8 @@ class Log(@volatile private var _dir: File,
           val topicPartition: TopicPartition,
           val producerStateManager: ProducerStateManager,
           logDirFailureChannel: LogDirFailureChannel,
-          private val hadCleanShutdown: Boolean = true) extends Logging with KafkaMetricsGroup {
+          private val hadCleanShutdown: Boolean = true,
+          val usesTopicId: Boolean = true) extends Logging with KafkaMetricsGroup {

Review comment:
       Could we add the new param to javadoc? Also, will keepPartitionMetdataFile be better than usesTopicId?

##########
File path: core/src/main/scala/kafka/server/PartitionMetadataFile.scala
##########
@@ -91,11 +91,10 @@ class PartitionMetadataFile(val file: File,
   private val lock = new Object()
   private val logDir = file.getParentFile.getParent
 
-
-  try Files.createFile(file.toPath) // create the file if it doesn't exist
-  catch { case _: FileAlreadyExistsException => }
-
   def write(topicId: Uuid): Unit = {
+    try Files.createFile(file.toPath) // create the file if it doesn't exist

Review comment:
       Do we need to create the file first? It seems that later on we always rename the temp file to this one.
   

##########
File path: core/src/test/scala/unit/kafka/log/LogManagerTest.scala
##########
@@ -217,6 +217,7 @@ class LogManagerTest {
     }
     assertTrue(log.numberOfSegments > 1, "There should be more than one segment now.")
     log.updateHighWatermark(log.logEndOffset)
+    log.partitionMetadataFile.get.write(Uuid.randomUuid())

Review comment:
       Is this needed? It seems Log never reads UUID? Ditto below.




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