ASF GitHub Bot commented on ZOOKEEPER-2872:
Github user hanm commented on a diff in the pull request:
--- Diff: src/java/main/org/apache/zookeeper/server/quorum/Learner.java ---
@@ -364,6 +364,7 @@ protected void syncWithLeader(long newLeaderZxid)
LinkedList<Long> packetsCommitted = new LinkedList<Long>();
LinkedList<PacketInFlight> packetsNotCommitted = new
+ boolean syncSnapshot = false;
--- End diff --
We can level this variable definition up so it's clustered with
Another possibility is to get ride of this variable and use existing
`snapshotNeeded` - but that will do fysnc snapshot for TRUNC sync, which the
existing patch will not.
> Interrupted snapshot sync causes data loss
> Key: ZOOKEEPER-2872
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2872
> Project: ZooKeeper
> Issue Type: Bug
> Components: server
> Affects Versions: 3.4.10, 3.5.3, 3.6.0
> Reporter: Brian Nixon
> There is a way for observers to permanently lose data from their local data
> tree while remaining members of good standing with the ensemble and
> continuing to serve client traffic when the following chain of events occurs.
> 1. The observer dies in epoch N from machine failure.
> 2. The observer comes back up in epoch N+1 and requests a snapshot sync to
> catch up.
> 3. The machine powers off before the snapshot is synced to disc and after
> some txn's have been logged (depending on the OS, this can happen!).
> 4. The observer comes back a second time and replays its most recent snapshot
> (epoch <= N) as well as the txn logs (epoch N+1).
> 5. A diff sync is requested from the leader and the observer broadcasts
> In this scenario, any commits from epoch N that the observer did not receive
> before it died the first time will never be exposed to the observer and no
> part of the ensemble will complain.
> This situation is not unique to observers and can happen to any learner. As a
> simple fix, fsync-ing the snapshots received from the leader will avoid the
> case of missing snapshots causing data loss.
This message was sent by Atlassian JIRA