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From Jordan Zimmerman <jor...@jordanzimmerman.com>
Subject Re: Use-case with lots of child nodes
Date Tue, 31 May 2016 16:30:30 GMT
The ZK jute limit is part of their protocol. Any API usage is limited to 1MB (unless you increase
it). In the case of getChildren(), that would be the value of any overheard for serialization
plus the concatenated length of the children names. The TL;DR is that you shouldn’t create
lots of children in ZK. Redesign your algorithm to spread out the children. This is a ZK issue
and not a Curator issue. 

-JZ

> On May 31, 2016, at 5:16 AM, Szekeres, Zoltan <Zoltan.Szekeres@morganstanley.com>
wrote:
> 
> 
> Hi Curator users,
>  
> I have a use-case where I need to create a very large number (~70,000)  of child nodes
under a parent. These nodes themselves contain no data and will only have a handful of child
nodes themselves.
> e.g.
> /someparentNode/LotsOfChildNodesHere-1/ACoupleofNodesAtThisLevel
> /someparentNode/LotsOfChildNodesHere-2/ACoupleofNodesAtThisLevel
> ...
> /someparentNode/LotsOfChildNodesHere-70000/ACoupleofNodesAtThisLevel
>  
> I've read (https://zookeeper.apache.org/doc/r3.4.8/zookeeperAdmin.html <https://zookeeper.apache.org/doc/r3.4.8/zookeeperAdmin.html>)
there is a limit of 1 MB. But I hit the limit for the getChildren operation around 4 MB. I'm
interested in what's causing the difference in the limit.
>  
> To give more detail I have a primary and secondary use-case:
> My primary use-case includes having watchers on the children of "/someparentNode" and
requesting getChildren for "/someparentNode/LotsOfChildNodesHere-N" (which only has a couple
child nodes).
> My secondary use-case would be requesting the children of "/someparentNode", which would
be only occasionally for reporting purposes (which has a lot of child nodes and probably won't
be as much as 70k nodes, but I hit the limit there).
>  
> I'm looking for answers for the following questions:
> What are the stability issues that you think might occur having lots of nodes under one
node, even if we read them rarely?
> Can I reliable use the "jute.maxbuffer" system property on the client in the future?
> Looking for answers whether the asymmetry of the default value on client side and on
server side is accidental or intentional.
>  
> Any advice is much appreciated.
>  
> Thanks,
> Zoltan Szekeres
> 
> 
> 
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