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Posted to issues@ozone.apache.org by "Copilot (via GitHub)" <gi...@apache.org> on 2026/08/13 05:23:48 UTC
Re: [PR] HDDS-16164. DirectoryDeletingService could deadlock snapshot purge while retaining snapshot DB handles [ozone]
Copilot commented on code in PR #11009:
URL: https://github.com/apache/ozone/pull/11009#discussion_r3772642279
##########
hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/om/service/DirectoryDeletingService.java:
##########
@@ -824,12 +920,25 @@ public BackgroundTaskResult call() {
} else if (!isPreviousPurgeTransactionFlushed()) {
return BackgroundTaskResult.EmptyTaskResult.newResult();
}
- try (UncheckedAutoCloseableSupplier<OmSnapshot> omSnapshot = snapInfo == null ? null :
- omSnapshotManager.getActiveSnapshot(snapInfo.getVolumeName(), snapInfo.getBucketName(),
- snapInfo.getName())) {
- KeyManager keyManager = snapInfo == null ? getOzoneManager().getKeyManager()
- : omSnapshot.get().getKeyManager();
- processDeletedDirsForStore(snapInfo, keyManager, run, pathLimitPerTask);
+ boolean snapshotProcessingLockAcquired = false;
+ try {
+ if (snapInfo != null) {
+ // Serialize snapshot setup before opening the snapshot DB. Workers still process each snapshot in
+ // parallel, but another snapshot task cannot wait here while retaining a task-owned DB handle.
+ snapshotProcessingLock.lockInterruptibly();
+ snapshotProcessingLockAcquired = true;
+ }
+ try (UncheckedAutoCloseableSupplier<OmSnapshot> omSnapshot = snapInfo == null ? null :
+ omSnapshotManager.getActiveSnapshot(snapInfo.getVolumeName(), snapInfo.getBucketName(),
+ snapInfo.getName())) {
+ KeyManager keyManager = snapInfo == null ? getOzoneManager().getKeyManager()
+ : omSnapshot.get().getKeyManager();
+ processDeletedDirsForStore(snapInfo, keyManager, omSnapshot, run, pathLimitPerTask);
+ }
+ } finally {
+ if (snapshotProcessingLockAcquired) {
+ snapshotProcessingLock.unlock();
+ }
}
Review Comment:
`snapshotProcessingLock` is held for the entire snapshot deletion task (including directory scanning and synchronous OM requests) even though the comment says it only serializes snapshot setup. With the BackgroundService pool size equal to the configured deletion threads, multiple snapshot tasks can end up blocking on this lock and occupy the service thread pool, delaying AOS work and other snapshots unnecessarily.
Consider limiting the lock scope to only the `getActiveSnapshot(...)` open (or other setup that must be serialized) and releasing it immediately afterward, before the potentially long-running `processDeletedDirsForStore(...)`.
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