klsince commented on a change in pull request #7969:
URL: https://github.com/apache/pinot/pull/7969#discussion_r780564787
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File path:
pinot-core/src/main/java/org/apache/pinot/core/data/manager/BaseTableDataManager.java
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@@ -480,12 +426,138 @@ File getSegmentDataDir(String segmentName) {
return new File(_indexDir, segmentName);
}
- @VisibleForTesting
- static boolean isNewSegment(SegmentZKMetadata zkMetadata, @Nullable
SegmentMetadata localMetadata) {
- return localMetadata == null || !hasSameCRC(zkMetadata, localMetadata);
+ /**
+ * Create a backup directory to handle failure of segment reloading.
+ * First rename index directory to segment backup directory so that original
segment have all file
+ * descriptors point to the segment backup directory to ensure original
segment serves queries properly.
+ * The original index directory is restored lazily, as depending on the
conditions,
+ * it may be restored from the backup directory or segment downloaded from
deep store.
+ */
+ private void createBackup(File indexDir) {
+ if (!indexDir.exists()) {
+ return;
+ }
+ File parentDir = indexDir.getParentFile();
+ File segmentBackupDir = new File(parentDir, indexDir.getName() +
CommonConstants.Segment.SEGMENT_BACKUP_DIR_SUFFIX);
+ // Rename index directory to segment backup directory (atomic).
+ Preconditions.checkState(indexDir.renameTo(segmentBackupDir),
+ "Failed to rename index directory: %s to segment backup directory:
%s", indexDir, segmentBackupDir);
+ }
+
+ /**
+ * Remove the backup directory to mark the completion of segment reloading.
+ * First rename then delete is as renaming is an atomic operation, but
deleting is not.
+ * When we rename the segment backup directory to segment temporary
directory, we know the reload
+ * already succeeded, so that we can safely delete the segment temporary
directory.
+ */
+ private void removeBackup(File indexDir)
+ throws IOException {
+ File parentDir = indexDir.getParentFile();
+ File segmentBackupDir = new File(parentDir, indexDir.getName() +
CommonConstants.Segment.SEGMENT_BACKUP_DIR_SUFFIX);
+ if (!segmentBackupDir.exists()) {
+ return;
+ }
+ File segmentTempDir = new File(parentDir, indexDir.getName() +
CommonConstants.Segment.SEGMENT_TEMP_DIR_SUFFIX);
Review comment:
As deletion happens immediately after renaming here, I'd assume naming
collision on this temp dir would be no harm.
Besides, deleting this tmp dir may fail or not get chance to happen (e.g.
upon JVM hard stop), so the LoaderUtils.reloadFailureRecovery method retries to
delete this tmp dir if it still exists. Adding a timestamp in the name would
add more complexity for this retry logic.
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