A raspberry pi or a apu board would be enough for your majority ZK node
in your 3rd room.
One kafka cluster belongs to one ZK cluster. You could have one ZK/Kafka
cluster per room. There are tools for one direction copying of Kafka
messages but bi-directional "replication" is not possible as far as I
know. It does not make much sense I think but it depends on the use-case.
Am 06.03.2017 um 20:37 schrieb Le Cyberian:
Hi Han,
Thank you for your response. I understand. Its not possible to have a third
rack/server room at the moment as the requirement is to have redundancy
between both. I tried already to get one :-/
Is it possible to have a Zookeeper Ensemble (3 node) in one server room and
same in the other and have some sort of master-master replication in
between both of them ? would this make sense if its possible ? since in
this case both would have same config and split brain theoretically should
not happen.
I haven't does this Zookeeper 3rd node hack before :) i guess i need to
play around with it for a while to get it proper documented and functional
/ tested :)
Thanks again!
Le
On Mon, Mar 6, 2017 at 8:22 PM, Hans Jespersen <h...@confluent.io> wrote:
Is there any way you can find a third rack/server room/power supply nearby
just for the 1 extra zookeeper node? You don’t have to put any kafka
brokers there, just a single zookeeper. It’s less likely to have a 3-way
split brain because of a network partition. It’s so much cleaner with 3
availability zones because everything would be automatic failover. This is
how most people run when deployed in Amazon.
Baring that I would say the next best thing would be 3 zookeepers in one
zone and 2 zookeepers in the other zone so it will auto-failover if the 2
zk zone fails. If the 3 zk zone fails you can setup a well tested set of
manual steps to carefully configure a 3rd zookeeper clone (which matches
the id of one of the failed nodes) and still get your system back up and
running. If this is not something you have done before I suggest getting a
few days of expert consulting to have someone help you set it up, test it,
and document the proper failover and recovery procedures.
-hans
On Mar 6, 2017, at 10:44 AM, Le Cyberian <lecyber...@gmail.com> wrote:
Thanks Han and Alexander for taking time out and your responses.
I now understand the risks and the possible outcome of having the desired
setup.
What would be better in your opinion to have failover (active-active)
between both of these server rooms to avoid switching to the clone / 3rd
zookeeper.
I mean even if there are 5 nodes having 3 in one server room and 2 in
other
still there would be problem related to zookeeper majority leader
election
if the server room goes down that has 3 nodes.
is there some way to achieve this ?
Thanks again!
Lee
On Mon, Mar 6, 2017 at 4:16 PM, Alexander Binzberger <
alexander.binzber...@wingcon.com> wrote:
I agree on this is one cluster but having one additional ZK node per
site
does not help. (as far as I understand ZK)
A 3 out of 6 is also not a majority. So I think you mean 3/5 with a
cloned
3rd one. This would mean manually switching the cloned one for majority
which can cause issues again.
1. You actually build a master/slave ZK with manually switch over.
2. While switching the clone from room to room you would have downtime.
3. If you switch on both ZK node clones at the same time (by mistake)
you
screwed.
4. If you "switch" clones instead of moving it will all data on disk you
generate a split brain from which you have to recover first.
So if you loose the connection between the rooms / the rooms get
separated
/ you loose one room:
* You (might) need manual interaction
* loose automatic fail-over between the rooms
* might face complete outage if your "master" room with the active 3rd
node is hit.
Actually this is the same scenario with 2/3 nodes spread over two
locations.
What you need is a third cross connected location for real fault
tolerance
and distribute your 3 or 5 ZK nodes over those.
Or live with a possible outage in such a scenario.
Additional Hints:
* You can run any number of Kafka brokers on a ZK cluster. In your case
this could be 4 Kafka brokers on 3 ZK nodes.
* You should set topic replication to 2 (can be done at any time) and
some
other producer/broker settings to ensure your messages will not get
lost in
switch over cases.
* ZK service does not react nicely on disk full.
Am 06.03.2017 um 15:10 schrieb Hans Jespersen:
In that case it’s really one cluster. Make sure to set different rack
ids
for each server room so kafka will ensure that the replicas always span
both floors and you don’t loose availability of data if a server room
goes
down.
You will have to configure one addition zookeeper node in each site
which
you will only ever startup if a site goes down because otherwise 2 of 4
zookeeper nodes is not a quorum.Again you would be better with 3 nodes
because then you would only have to do this in the site that has the
single
active node.
-hans
On Mar 6, 2017, at 5:57 AM, Le Cyberian <lecyber...@gmail.com> wrote:
Hi Hans,
Thank you for your reply.
Its basically two different server rooms on different floors and they
are
connected with fiber connectivity so its almost like a local
connection
between them no network latencies / lag.
If i do a Mirror Maker / Replicator then i will not be able to use
them
at
the same time for writes./ producers. because the consumers /
producers
will request from all of them
BR,
Lee
On Mon, Mar 6, 2017 at 2:50 PM, Hans Jespersen <h...@confluent.io>
wrote:
What do you mean when you say you have "2 sites not datacenters"? You
should be very careful configuring a stretch cluster across multiple
sites.
What is the RTT between the two sites? Why do you think that MIrror
Maker
(or Confluent Replicator) would not work between the sites and yet
you
think a stretch cluster will work? That seems wrong.
-hans
/**
* Hans Jespersen, Principal Systems Engineer, Confluent Inc.
* h...@confluent.io (650)924-2670
*/
On Mon, Mar 6, 2017 at 5:37 AM, Le Cyberian <lecyber...@gmail.com>
wrote:
Hi Guys,
Thank you very much for you reply.
The scenario which i have to implement is that i have 2 sites not
datacenters so mirror maker would not work here.
There will be 4 nodes in total, like 2 in Site A and 2 in Site B.
The
idea
is to have Active-Active setup along with fault tolerance so that if
one
of
the site goes on the operations are normal.
In this case if i go ahead with 4 node-cluster of both zookeeper and
kafka
it will give failover tolerance for 1 node only.
What do you suggest to do in this case ? because to divide between 2
sites
it needs to be even number if that makes sense ? Also if possible
some
help
regarding partitions for topic and replication factor.
I already have Kafka running with quiet few topics having
replication
factor 1 along with 1 default partition, is there a way to
repartition
/
increase partition of existing topics when i migrate to above setup
? I
think we can increase replication factor by Kafka rebalance tool.
Thanks alot for your help and time looking into this.
BR,
Le
On Mon, Mar 6, 2017 at 12:20 PM, Hans Jespersen <h...@confluent.io>
wrote:
Jens,
I think you are correct that a 4 node zookeeper ensemble can be
made
to
work but it will be slightly less resilient than a 3 node ensemble
because
it can only tolerate 1 failure (same as a 3 node ensemble) and the
likelihood of node failures is higher because there is 1 more node
that
could fail.
So it SHOULD be an odd number of zookeeper nodes (not MUST).
-hans
On Mar 6, 2017, at 12:20 AM, Jens Rantil <jens.ran...@tink.se>
wrote:
Hi Hans,
On Mon, Mar 6, 2017 at 12:10 AM, Hans Jespersen <
h...@confluent.io>
wrote:
A 4 node zookeeper ensemble will not even work. It MUST be an odd
number
of zookeeper nodes to start.
Are you sure about that? If Zookeer doesn't run with four nodes,
that
means
a running ensemble of three can't be live-migrated to other nodes
(because
that's done by increasing the ensemble and then reducing it in the
case
of
3-node ensembles). IIRC, you can run four Zookeeper nodes, but
that
means
quorum will be three nodes, so there's no added benefit in terms of
availability since you can only loose one node just like with a
three
node
cluster.
Cheers,
Jens
--
Jens Rantil
Backend engineer
Tink AB
Email: jens.ran...@tink.se
Phone: +46 708 84 18 32
Web: www.tink.se
Facebook <https://www.facebook.com/#!/tink.se> Linkedin
<http://www.linkedin.com/company/2735919?trk=vsrp_
companies_res_photo&trkInfo=VSRPsearchId%3A1057023381369207406670%
2CVSRPtargetId%3A2735919%2CVSRPcmpt%3Aprimary>
Twitter <https://twitter.com/tink>
--
Alexander Binzberger
System Designer - WINGcon AG
Tel. +49 7543 966-119
Sitz der Gesellschaft: Langenargen
Registergericht: ULM, HRB 734260
USt-Id.: DE232931635, WEEE-Id.: DE74015979
Vorstand: thomasThomas Ehrle (Vorsitz), Fritz R. Paul (Stellvertreter), Tobias
Treß
Aufsichtsrat: Jürgen Maucher (Vorsitz), Andreas Paul (Stellvertreter), Martin
Sauter
