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From Abraham Fine <af...@apache.org>
Subject Re: Zookeeper client reverse lookup issue
Date Tue, 21 Nov 2017 22:18:19 GMT
I don't think a backport would be possible here (since existing
deployments may break when upgraded within the 3.4 line). If a fix can
be created without changing existing ZooKeeper behavior by default that
would be much more likely to be considered. Perhaps in the form of a
configuration switch of some kind. 

In short we need to consider this from two angles. 3.4 is broken because
this is unexpected behavior and 3.5 is broken because ZOOKEEPER-2171
broke backwards compatibility. So I think we should add in a switch with
opposite default values for 3.4 and 3.5.

Would you be interested in submitting a patch for this Ben?

Thanks,
Abe

On Mon, Nov 20, 2017, at 15:11, Ben Wood wrote:
> Do you think a patch targeting 3.4.11 or 3.4.12 that backports this
> lookup
> change (as minimally as possible) would be accepted?
> 
> In order to do ZK in containers (yes, slightly terrifying), it's not
> _necessary_ but a lot easier!
> 
> On Mon, Nov 20, 2017 at 12:34 PM, Abraham Fine <afine@apache.org> wrote:
> 
> > Hi Ben-
> >
> > Unfortunately 3.5 is still in beta and not recommended for production.
> >
> > Thanks,
> > Abe
> >
> > On Mon, Nov 20, 2017, at 11:13, Ben Wood wrote:
> > > Hey Abraham,
> > >
> > > We've been using 3.4.11.[
> > >
> > > That's great news the reverse lookup has already been taken out in 3.5!
> > > We
> > > found another ticket https://issues.apache.org/
> > jira/browse/ZOOKEEPER-2858
> > > that suggested there were some workarounds but hadn't found that one (and
> > > hadn't had a chance to test 3.5).
> > >
> > > This raises an interesting question for us, admitted ZK neophytes, is ZK
> > > 3.5 "safe" to use in production?
> > >
> > > On Fri, Nov 17, 2017 at 3:11 PM, Abraham Fine <afine@apache.org> wrote:
> > >
> > > > This change occurred due to
> > > > https://issues.apache.org/jira/browse/ZOOKEEPER-2171
> > > >
> > > > On Fri, Nov 17, 2017, at 15:10, Abraham Fine wrote:
> > > > > Hi Ben-
> > > > >
> > > > > What version of ZooKeeper are you using? In my testing it looks like
> > 3.4
> > > > > does a reverse lookup when creating the server principal
> > > > > (https://github.com/apache/zookeeper/blob/branch-3.4/src/
> > > > java/main/org/apache/zookeeper/ClientCnxn.java#L1011)
> > > > > but 3.5/master do not
> > > > > (https://github.com/apache/zookeeper/blob/branch-3.5/src/
> > > > java/main/org/apache/zookeeper/ClientCnxn.java#L1104).
> > > > >
> > > > > Let me know if that helps.
> > > > >
> > > > > Thanks,
> > > > > Abe
> > > > >
> > > > > On Fri, Nov 17, 2017, at 12:01, Ben Wood wrote:
> > > > > > Hey Folks,
> > > > > >
> > > > > > My team and I are working on a containerized Zookeeper service
on
> > top
> > > > of
> > > > > > DC/OS. We're running into an issue with Kerberos in the following
> > > > > > scenario.
> > > > > >
> > > > > > Simplified, we have a zk server with the DNS address zk-server.dcos
> > > > (e.g.
> > > > > > the dns address of the ZK task) and actual hostname zk-server.aws
> > > > > > (Shortened here, but really a standard resolvable AWS private
dns
> > > > > > address)
> > > > > > and a kafka broker, kafka.dcos.
> > > > > >
> > > > > > We can easily setup our Zookeeper and Kafka services to work
> > together,
> > > > > > until we try to enable Kerberos. ZK itself works just fine with
> > > > Kerberos,
> > > > > > but the Kafka broker is not able to connect to the ZK server:
> > > > > >
> > > > > > 0. kafka.dcos is started with a zk server list of zk-server.dcos.
> > > > > > 1. kafka.dcos starts up, initializing its ZK client.
> > > > > > 2. kafka.dcos then attempts to retrieve a ticket from the KDC
in
> > order
> > > > to
> > > > > > talk to zk-server.aws, however the only zk principal known to
the
> > kdc
> > > > is
> > > > > > zk-server.dcos.
> > > > > >
> > > > > > From reading the source (
> > > > > > https://github.com/apache/zookeeper/blob/master/src/
> > > > java/main/org/apache/zookeeper/client/StaticHostProvider.java#L112)
> > > > > > it appears that the zk client is winding up with the actual
> > hostname of
> > > > > > the
> > > > > > ZK server.
> > > > > >
> > > > > > Being new to the codebase, is this because of a client reverse
> > lookup?
> > > > Or
> > > > > > because the zk server is telling the client about its hostname?
It
> > > > > > appears
> > > > > > to be the former.
> > > > > >
> > > > > > Thanks!
> > > > > > Ben
> > > >
> > >
> > >
> > >
> > > --
> > > Ben Wood
> > > Software Engineer - Data Agility
> > > Mesosphere
> >
> 
> 
> 
> -- 
> Ben Wood
> Software Engineer - Data Agility
> Mesosphere

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