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Date: Fri, 18 Mar 2016 16:48:43 +0000
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Subject: Re: Dealing with old delivered requests in memory
From: ibrahim El-sanosi <ibrahimsabattt@gmail.com>
To: user@zookeeper.apache.org
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Thank you Jordan,

So as "ZooKeeper stores the entire database in memory. ZNodes exist until
deleted.". As we know the memory size is limited, we expect the
OutOfMemoryError
excption could occur even we set the Max heap size as maxumim value as
possible?

Ibrahim


On Fri, Mar 18, 2016 at 4:40 PM, Jordan Zimmerman <
jordan@jordanzimmerman.com> wrote:

> ZooKeeper stores the entire database in memory. Logs are for durability
> only. ZNodes exist until deleted.
>
> -Jordan
>
> > On Mar 18, 2016, at 11:38 AM, ibrahim El-sanosi <
> ibrahimsabattt@gmail.com> wrote:
> >
> > Thank you for replaying.
> >
> >
> > Take this example, Zookeeper started on 1/1/2015, and assume ZK servers
> are
> > never crashed. Also, the ZK are very busy, reciveing continusly write
> > requests from clients and accordingly snapshots are generated overtime.
> On
> > 1/3/2015, what  Znodes will be in memory data tree? do all Znodes still
> > store in memory (from 1/1/2015 to 1/3/2015) as there is no crashed occur.
> > Or Dsnapshhot is taken the data tree is
> >
> >
> > Note that  I am not asking about data in log or snapshoot. I am asking
> > about the current data in memory.
> >
> > On Fri, Mar 18, 2016 at 4:12 PM, Flavio Junqueira <fpj@apache.org>
> wrote:
> >
> >> Hi Ibrahim,
> >>
> >> Are you asking about how we compact old logs? We do it by taking
> snapshots
> >> so that upon recovery, we only load the latest snapshot and replay the
> txn
> >> log from the snapshot tag. The snapshot tag is the last zxid committed
> when
> >> we start producing the snapshot.
> >>
> >> We don't actually delete anything, though, unless you intentionally turn
> >> on auto purge:
> >>
> >>
> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
> >> <
> >>
> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
> >>>
> >>
> >> -Flavio
> >>
> >>> On 18 Mar 2016, at 16:05, ibrahim El-sanosi <ibrahimsabattt@gmail.com>
> >> wrote:
> >>>
> >>> Hi all,
> >>>
> >>> Assume the Zookeeper have been running for about one year (from
> 1/1/2015
> >>> until now), how does ZooKeeper deal with old delivered write requests
> (To
> >>> optimize a memory used) (say from 1/1/2015 to 03/04/2015). I am
> assuming
> >>> the old delivered request are no longer used.
> >>>
> >>> On the other words, what strategy ZK does to find and delete unused
> >> Znodes?
> >>>
> >>> Ibrahim
> >>
> >>
>
>

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