zookeeper-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Michael Han <h...@cloudera.com>
Subject Re: Zookeeper in two data centers and disaster recovery
Date Sun, 11 Dec 2016 04:38:41 GMT
Read only mode needs to be enabled on both client and server side. Once
enabled, if a server is partitioned from the quorum, it will be in read
only mode and serving only read only client. Client that's not enabled with
read only mode will not connect to the read only server. Client that's
enabled with read only mode can connect to read only server but any write
operation will fail.

On Fri, Dec 9, 2016 at 12:10 PM, Alvaro Gareppe <agareppe@gmail.com> wrote:

> Thank you very much for your response..
>
> Maybe the read only mode can be an option in this case. But how does it
> works ? It olny allows conections that are read only ? or allows any
> connection but fails on write operations ?
>
>
>
>
>
>
> On Thu, Dec 8, 2016 at 10:05 PM, Michael Han <hanm@cloudera.com> wrote:
>
> > If "keep running" is defined as serving both read and write requests then
> > no there is no way to build a reliable ZooKeeper ensemble across only two
> > data centers simply because we can't guarantee that the single data
> center
> > remaining after another one is lost contains the majority number of
> servers
> > that can form a quorum. In this case you need at least 3 DC. If "keep
> > running" is defined as serving only read requests then you could enable
> > read only mode of ZK server so if a DC failed and remaining servers fail
> to
> > form a quorum, your application can still read data out of ZK, but no
> write
> > would be done after the point.
> >
> > In general cross DC deployment design depends on your use case and trade
> > offs you'd like to make. Similar topic was well discussed before [1], and
> > there is a recent paper [2] which also provides good reference on this
> > topic.
> >
> > [1]
> > http://zookeeper-user.578899.n2.nabble.com/zookeeper-
> > deployment-strategy-for-multi-data-centers-td7582358.html#a7582364
> > [2]
> > https://www.usenix.org/system/files/conference/atc16/atc16_
> > paper-lev-ari.pdf
> >
> > On Thu, Dec 8, 2016 at 10:16 AM, Alvaro Gareppe <agareppe@gmail.com>
> > wrote:
> >
> > > I have Zookeeper running in a PRD environment with 3 instances
> running. 2
> > > in 1 data center and 1 in other. But as zookeeper ensamble runs with a
> > > majority if a loose the data center that runs 2 nodes of zookeeper, I
> > loose
> > > the cluster.
> > >
> > > Is there any way to configure zookeeper (even adding more nodes is an
> > > option) to keep running if some of the data center is offline (any one
> of
> > > them). The only restiction, of course, is the number of datacenters
> > >
> > > --
> > > Ing. Alvaro Gareppe
> > > agareppe@gmail.com
> > >
> >
> >
> >
> > --
> > Cheers
> > Michael.
> >
>
>
>
> --
> Ing. Alvaro Gareppe
> agareppe@gmail.com
>



-- 
Cheers
Michael.

Mime
  • Unnamed multipart/alternative (inline, None, 0 bytes)
View raw message