Thanks for Flavio Junqueira for your response. assume C received the commit request but before committing it failed, When C will be synced? What event will at leader or follower will synch it up.
Here is another scenario we faced. Node got deleted successfully in leader node B. But due to network issue in Master node, the delete could not sync up to follower A and C. At this moment, Leader node also goes down as faulty. Now one of the A and C becomes leader but it has inconsistent data. ( delete is not executed here) As I know, This behavior is fine as per current ZK design. But to solve above data inconsistency issue, any suggestions ? I thought to commit the delete not only in leader but to at least in N/2 nodes in the same client call and then only mark delete as successful Any suggestions ? Best Regards Mohammad Arshad -----Original Message----- From: Flavio Junqueira [mailto:f...@apache.org] Sent: 21 January 2016 19:11 To: u...@zookeeper.apache.org Cc: dev Subject: Re: How to handle zookeeper data inconsistency Hi Mohammad, A delete operation only needs to reach a quorum to complete and A B form a quorum in your 3-server ensemble. If the delete operation never gets propagated to C and other write operations that have been ordered later complete on C, then you have an issue. If C simply stops receiving updates, then you have a problem with your C server and it could be a problem with ZK or just the environment. If there has been write operations ordered after the delete and server C has seen those but not the delete, then I'd recommend that you have a look the txn logs with the log formatter. > shall I check exists from leader only? but even leader can have some > node undeleted in the above scenario There is no such a requirement, but you need to be aware that server C could definitely make an update visible later compared to other servers. ZooKeeper doesn't guarantee that updates are visible to all clients as soon as they are acknowledged. I'd also search for jiras, especially if you're deleting an ephemeral. -Flavio > On 21 Jan 2016, at 13:24, Mohammad arshad <mohammad.ars...@huawei.com> wrote: > > Hi All, > I came across a scenario where zookeeper was left in inconsistent > state(but that is valid as per the zookeeper theory) and because of > that dependent application's behaved wrongly The scenario is as follow > > 1) I have three server Zookeeper cluster, let's say servers are A, B > and C. B is the leader > 2) In one successful delete operation, a znode znode1 was deleted from A and > B but somehow not deleted from C. The reason for not deleted from C can be > either proposal or commit failed. > 3) Now for application, which is connected to C, ZooKeeper.exists > returns the znod1 and that is why application enters into node exists > flow which is wrong > > shall I check exists from leader only? but even leader can have some > node undeleted in the above scenario Any guideline to handle the above said > valid data inconsistency ?? > > Any suggestion/help is highly appreciated. > > Best Regards > Mohammad Arshad > HUAWEI TECHNOLOGIES CO.LTD. > Huawei Tecnologies India Pvt. Ltd. > Near EPIP Industrial Area, Kundalahalli Village Whitefield, > Bangalore-560066 www.huawei.com<http://www.huawei.com/> > ---------------------------------------------------------------------- > ------------------------------------------- > This e-mail and its attachments contain confidential information from > HUAWEI, which is intended only for the person or entity whose address > is listed above. Any use of the information contained herein in any > way (including, but not limited to, total or partial disclosure, > reproduction, or dissemination) by persons other than the intended > recipient(s) is prohibited. If you receive this e-mail in error, > please notify the sender by phone or email immediately and delete it! >
