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From Alexander Shraer <shra...@gmail.com>
Subject Re: New to zookeeper
Date Wed, 12 Jul 2017 22:02:13 GMT
Just a small comment - 3.5.3 is in beta. The getConfig API returns a list
of servers in the cluster, including their ports and roles in the ensemble.


On Wed, Jul 12, 2017 at 7:53 AM, Washko, Daniel <dwashko@gannett.com> wrote:

> I speak strictly from my experience with Zookeeper and not an any official
> capacity of the project or of exhibitor.
> Exhibitor works great and allows you to easily automate clustering
> zookeeper nodes into an ensemble and discovering the individual nodes in
> the ensemble via an http call. We ran into a problem, though, after we
> implemented Exhibitor across our infrastructure. Every so often our
> Zookeeper ensembles lost the data they stored. While I cannot say this was
> caused by Exhibitor, we have Solr clouds where Exhibitor was not used and
> they never had this problem. My suspicion is that there was a problem with
> a zookeeper node and Exhibitor removed that node from the ensemble then did
> a rolling restart. When that node recovered for some reason the data was
> corrupted or lost. Exhibitor pulled that node back into the ensemble and
> did a rolling restart. That node became leader and when the others joined
> synced from that. Those nodes then dumped their data stored to be in sync
> with the leader. This is my speculation, I have had a very hard time
> replicating this and have not heard of anyone else having this problem.
> Again, I am not definitively saying Exhibitor is the cause of this but
> since we removed Exhibitor this problem has not occurred.
> Zookeeper 3.5.x branch adds discovery functionality and does automated
> clustering. It’s great, but from what I understand is still in alpha.
> Prior to the 3.5.x branch I know of no way to discover what nodes are
> actually in the ensemble. The 4 letter commands will tell you whether a
> node is in an ensemble, whether it is a leader or follower, but it will not
> tell you what ensemble it is in or list any other node information. If
> someone has a way to do this please post, because I have looked all over.
> We make use of Scalr and that adds an additional layer to automation. I
> run orchestration scripts in Scalr that discover the other running
> zookeeper nodes in (what Scalr calls) the same Farm Role. This script
> configures each node with the information for the other nodes and does a
> restart of Zookeeper to bring them into an ensemble. Then it collects this
> information and stores the IP addresses into a Global Variable in scalr
> that is available then to Solr. Changes to the ensemble are reflected in
> this variable that is then passed to the Solr cloud where a restart of the
> service will update the zookeeper information in Solr. We are working
> towards moving this functionality to Consul where it will register ther
> zookeeper ensemble information allowing Solr to pull it from Consul as
> opposed to relying on Global Variables. What I am getting at is that
> outside the 3.5.x branch, automating this takes a bit of work.
> --
> Daniel S Washko
> Solutions Architect
> dwashko@gannett.com  <http://www.gannett.com/>
> On 7/11/17, 6:58 PM, "Luigi Tagliamonte" <luigi.tagliamonte86@gmail.com>
> wrote:
>     Hello, Zookeeper Users!
>     I'm currently configuring/exploring zookeeper.
>     I'm reading a lot about ensembles and scaling and I got some question
> that
>     I'd like to submit to an expert audience.
>     I need zookeeper as Kafka dependency so my deployment goal is the
> ensemble
>     reliability especially because last Kafka version uses zookeeper only
> to
>     store the leader partition.
>     Here are my questions:
>     - To manage the ensemble I decided to use exhibitor - what do you think
>     about? Should I look to something else?
>     - Is there a way to discover all the servers of an ensemble apart from
>     use 4LTR? I wonder if it is possible to do something like in Cassandra
> were
>     you contact one node and you can get the whole cluster info from it.
> should
>     I configure just a DNS per zookeeper server, this doesn't scale well
> in a
>     dynamic env like servers in autoscaling.
>     - is there any white paper that shows a real scalable and reliable
>     Zookeeper installation? Any resources are welcome!
>     Thank you all in advance!
>     Regards

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