dengziming commented on a change in pull request #10431: URL: https://github.com/apache/kafka/pull/10431#discussion_r627931196
########## File path: core/src/main/scala/kafka/raft/KafkaMetadataLog.scala ########## @@ -242,85 +246,125 @@ final class KafkaMetadataLog private ( } override def readSnapshot(snapshotId: OffsetAndEpoch): Optional[RawSnapshotReader] = { - try { - if (snapshotIds.contains(snapshotId)) { - Optional.of(FileRawSnapshotReader.open(log.dir.toPath, snapshotId)) - } else { - Optional.empty() + snapshots synchronized { + val reader = snapshots.get(snapshotId) match { + case None => + // Snapshot doesn't exists + None + case Some(None) => + // Snapshot exists but has never been read before + try { + val snapshotReader = Some(FileRawSnapshotReader.open(log.dir.toPath, snapshotId)) + snapshots.put(snapshotId, snapshotReader) + snapshotReader + } catch { + case _: NoSuchFileException => + // Snapshot doesn't exists in the data dir; remove + val path = Snapshots.snapshotPath(log.dir.toPath, snapshotId) + warn(s"Couldn't read $snapshotId; expected to find snapshot file $path") + snapshots.remove(snapshotId) + None + } + case Some(value) => + // Snapshot exists and it is already open; do nothing + value } - } catch { - case _: NoSuchFileException => - Optional.empty() + + reader.asJava.asInstanceOf[Optional[RawSnapshotReader]] } } override def latestSnapshotId(): Optional[OffsetAndEpoch] = { - val descending = snapshotIds.descendingIterator - if (descending.hasNext) { - Optional.of(descending.next) - } else { - Optional.empty() + snapshots synchronized { Review comment: Thanks for the explanations -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org