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Rakesh R commented on ZOOKEEPER-2574: ------------------------------------- Thank you [~abhishekrai]. I could see there are few more corrections required in the [zookeeperAdmin.html#The+Log+Directory|https://zookeeper.apache.org/doc/r3.4.9/zookeeperAdmin.html#The+Log+Directory], right?. I'd suggest you to read the {{ZooKeeper transaction log and snapshot}} related sections in the ZK docs and do necessary changes. Appreciate your time & efforts. {code} The Log Directory: A new log file is started each time a snapshot is begun. The log file's suffix is the first zxid written to that log {code} Could you please create a pull request for the proposed patch, that will be used for code reviews and commits. Hi [~fpj], [~phunt], [~rgs]. As part of this jira we have came across a situation {{"where snapshotting has happened multiple times without accompanying log rollover"}}, this is contradicting with the ZooKeeper docs. I think, this would be a serious concern in the view of disaster recovery scripts. If someone has written a script blindly following that "A new log file is started each time a snapshot is begun". It would be really helpful if you could pitch in and give your thoughts on this problem. Thanks! > PurgeTxnLog can inadvertently delete required txn log files > ----------------------------------------------------------- > > Key: ZOOKEEPER-2574 > URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2574 > Project: ZooKeeper > Issue Type: Bug > Components: server > Affects Versions: 3.4.7, 3.4.8, 3.5.0, 3.5.1, 3.5.2 > Environment: Zookeeper 3.4.8, standalone, and 3-server quorum > Reporter: Abhishek Rai > Assignee: Abhishek Rai > Priority: Blocker > Fix For: 3.4.10, 3.5.3 > > Attachments: ZOOKEEPER-2574.2.patch, ZOOKEEPER-2574.3.patch, > ZOOKEEPER-2574.4.patch, ZOOKEEPER-2574.5.patch, ZOOKEEPER-2574.6.patch, > ZOOKEEPER-2574.patch > > > As part of the fix for ZOOKEEPER-1797, the call to > FileTxnSnapLog.getSnapshotLogs() was removed from PurgeTxnLog.java. As a > result, some old-looking but required txn log files can be deleted, resulting > in data corruption or loss. > For example, consider the following: > 1. Configuration: > autopurge.snapRetainCount=3 > 2. Following files exist: > log.100 spans transactions from zxid=100 till zxid=140 (inclusive) > snapshot.110 - snapshot as of zxid=110 > snapshot.120 - snapshot as of zxid=120 > snapshot.130 - snapshot as of zxid=130 > Above scenario is possible when snapshotting has happened multiple times but > without accompanying log rollover, which is possible if the server was > running as a learner. > 3. PurgeTxnLog retains all snapshots but deletes log.100 because its zxid is > older than the zxid of the oldest snapshot (110). This results in loss of > transactions in the range 131-140. > Before the fix for ZOOKEEPER-1797, this was avoided by the call to > FileTxnSnapLog.getSnapshotLogs() which finds and retains the newest txn log > file with starting zxid < oldest retained snapshot's highest zxid. -- This message was sent by Atlassian JIRA (v6.3.4#6332)