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From Andor Molnar <an...@apache.org>
Subject Re: Why are errors stored in the transaction logs?
Date Tue, 29 Oct 2019 05:59:26 GMT
Hi Sylvain,

That should not be the case. Txns are not going to be created from read requests and not hit
SyncRequestProcessor which is responsible for maintaining txn and snap logs.

The error handling you see in processTxn() is for ignoring failures during log replaying inside
processTxn() method (in the catch branch). Introduced in ZOOKEEPER-1269 and it’s related
to multis afaics.


> On 2019. Oct 15., at 16:33, Sylvain Wallez <sylvain@apache.org> wrote:
> Hi ZooKeepers,
> We had an issue recently with a service hammering ZK to read a path that doesn't exist.
As a result the transaction logs grew quickly because errors are stored there.
> Looking at DataTree.processTxn() which is called from FileTxnSnapLog.restore() it seems
that errors read in the transaction log are essentially ignored.
> So what is storing errors in the txnlog useful for? Would it make sense to have a configuration
flag to not store them?
> Thanks,
> Sylvain

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