[HDDS-10408] NPE causes OM crash in Snapshot Purge request

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.5.0, 1.4.1
• Labels: pull-request-available
• Target Version/s: 1.4.1
• Assignee: Aswin Shakil
• Reporter: Aswin Shakil
• Created: 21/Feb/24 20:58
• Updated: 10/Apr/24 08:14
• Resolved: 22/Feb/24 19:03

Description

When a previous request has already purged the snapshot. There will be a race condition between SnapshotDeletingService and Snapshot Purge request. where we resend the same request. We can ignore this request as this snapshot is already purged.

2024-02-14 21:50:59,574 [OM StateMachine ApplyTransaction Thread - 0] WARN org.apache.hadoop.ozone.om.snapshot.SnapshotCache: Key: '/vol-yu9w1/buck-kmkp4/snap1707922796' does not exist in cache.
2024-02-14 21:50:59,907 [OM StateMachine ApplyTransaction Thread - 0] ERROR org.apache.hadoop.ozone.om.ratis.OzoneManagerStateMachine: Terminating with exit status 1: Request cmdType: SnapshotPurge
clientId: "client-62D7790F8E6C"SnapshotPurgeRequest {
  snapshotDBKeys: "/vol-yu9w1/buck-kmkp4/snap1707922796"}
 failed with exception
java.lang.NullPointerException
        at org.apache.hadoop.ozone.om.snapshot.SnapshotUtils.getNextActiveSnapshot(SnapshotUtils.java:152)
        at org.apache.hadoop.ozone.om.request.snapshot.OMSnapshotPurgeRequest.validateAndUpdateCache(OMSnapshotPurgeRequest.java:99)
        at org.apache.hadoop.ozone.protocolPB.OzoneManagerRequestHandler.handleWriteRequest(OzoneManagerRequestHandler.java:375)
        at org.apache.hadoop.ozone.om.ratis.OzoneManagerStateMachine.runCommand(OzoneManagerStateMachine.java:568)
        at org.apache.hadoop.ozone.om.ratis.OzoneManagerStateMachine.lambda$1(OzoneManagerStateMachine.java:359)
        at java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1604)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)

Issue Links

• is duplicated by: HDDS-10421 [Snapshot] OM corruption due to NullPointerException
• links to: GitHub Pull Request #6250