xuanyuanking commented on a change in pull request #32933:
URL: https://github.com/apache/spark/pull/32933#discussion_r661304791
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/state/RocksDBFileManager.scala
##########
@@ -153,6 +156,139 @@ class RocksDBFileManager(
logInfo(s"Saved checkpoint file for version $version")
}
+ /**
+ * Load all necessary files for specific checkpoint version from DFS to
given local directory.
+ * If version is 0, then it will deleted all files in the directory. For
other versions, it
+ * ensures that only the exact files generated during checkpointing will be
present in the
+ * local directory.
+ */
+ def loadCheckpointFromDfs(version: Long, localDir: File):
RocksDBCheckpointMetadata = {
+ logInfo(s"Loading checkpoint files for version $version")
+ val metadata = if (version == 0) {
+ if (localDir.exists) Utils.deleteRecursively(localDir)
+ localDir.mkdirs()
+ RocksDBCheckpointMetadata(Seq.empty, 0)
+ } else {
+ // Delete all non-immutable files in local dir, and unzip new ones from
DFS commit file
+ listRocksDBFiles(localDir)._2.foreach(_.delete())
+ Utils.unzipFromFile(fs, dfsBatchZipFile(version), localDir)
+
+ // Copy the necessary immutable files
+ val metadataFile = localMetadataFile(localDir)
+ val metadata = RocksDBCheckpointMetadata.readFromFile(metadataFile)
+ logInfo(s"Read metadata for version $version:\n${metadata.prettyJson}")
+ loadImmutableFilesFromDfs(metadata.immutableFiles, localDir)
+ versionToRocksDBFiles.put(version, metadata.immutableFiles)
+ metadataFile.delete()
+ metadata
+ }
+ logFilesInDir(localDir, s"Loaded checkpoint files for version $version")
+ metadata
+ }
+
+ /** Get the latest version available in the DFS directory. If no data
present, it returns 0. */
+ def getLatestVersion(): Long = {
+ val path = new Path(dfsRootDir)
+ if (fm.exists(path)) {
+ fm.list(path, onlyZipFiles)
+ .map(_.getPath.getName.stripSuffix(".zip"))
+ .map(_.toLong)
+ .foldLeft(0L)(math.max)
+ } else {
+ 0
+ }
+ }
+
+ /**
+ * Delete old versions by deleting the associated version and SST files.
+ * At a high-level, this method finds which versions to delete, and which
SST files that were
+ * last used in those versions. Its safe to delete these SST files because a
SST file can
+ * be reused only in successive versions. Therefore, if a SST file F was
last used in version
+ * V, then it wont be used in version V+1 or later, and if version V can be
deleted, then
+ * F can safely be deleted as well.
+ *
+ * To find old files, it does the following.
+ * - List all the existing [version].zip files
+ * - Find the min version that needs to be retained based on the given
`numVersionsToRetain`.
+ * - Accordingly decide which versions should be deleted.
+ * - Resolve all SSTs files of all the existing versions, if not already
resolved.
+ * - Find what was the latest version in which each SST file was used.
+ * - Delete the files that were last used in the to-be-deleted versions as
we will not
+ * need those files any more.
+ *
+ * Note that it only deletes files that it knows are safe to delete.
+ * It may not delete the following files.
+ * - Partially written SST files
+ * - SST files that were used in a version, but that version got overwritten
with a different
+ * set of SST files.
Review comment:
Yep, that's right.
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