You are viewing a plain text version of this content. The canonical link for it is here.
Posted to users@kafka.apache.org by Le Cyberian <le...@gmail.com> on 2017/03/05 21:46:53 UTC
Having 4 Node Kafka Cluster
Hi Guys,
I have a scenario where i need to configure a 4 node Kafka Cluster along
with Zookeeper having 4 nodes as well.
I understand as a rule of them when it comes to cluster its always odd
number, however this is the case i need to do it.
For zookeeper, i understand with a 4 node cluster i can tolerate failure of
1 node which is same as having a 3 node cluster which does not give benefit
of having 4th one. how does it effect when it comes to leader election ?
For Kafka its the same case, I wanted to understand if we really want to do
this and achieve fault tolerance some how.
Thanks!
Lee
Re: Having 4 Node Kafka Cluster
Posted by Alexander Binzberger <al...@wingcon.com>.
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 <ha...@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\u2019t have to put any kafka
>> brokers there, just a single zookeeper. It\u2019s less likely to have a 3-way
>> split brain because of a network partition. It\u2019s 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 <le...@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.binzberger@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\u2019s 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\u2019t 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 <le...@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 <ha...@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.
>>>>>>> * hans@confluent.io (650)924-2670
>>>>>>> */
>>>>>>>
>>>>>>> On Mon, Mar 6, 2017 at 5:37 AM, Le Cyberian <le...@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 <ha...@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 <je...@tink.se>
>>>>>>>>> wrote:
>>>>>>>> Hi Hans,
>>>>>>>>>> On Mon, Mar 6, 2017 at 12:10 AM, Hans Jespersen <
>> hans@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.rantil@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 Tre�
Aufsichtsrat: J�rgen Maucher (Vorsitz), Andreas Paul (Stellvertreter), Martin Sauter
Re: Having 4 Node Kafka Cluster
Posted by Le Cyberian <le...@gmail.com>.
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 <ha...@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 <le...@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.binzberger@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 <le...@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 <ha...@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.
> >>>>> * hans@confluent.io (650)924-2670
> >>>>> */
> >>>>>
> >>>>> On Mon, Mar 6, 2017 at 5:37 AM, Le Cyberian <le...@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 <ha...@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 <je...@tink.se>
> >>>>>>>>
> >>>>>>> wrote:
> >>>>>
> >>>>>> Hi Hans,
> >>>>>>>>
> >>>>>>>> On Mon, Mar 6, 2017 at 12:10 AM, Hans Jespersen <
> hans@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.rantil@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>
> >>>>>>>>
> >>>>>>>
> >>>
> >>
>
>
Re: Having 4 Node Kafka Cluster
Posted by Hans Jespersen <ha...@confluent.io>.
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 <le...@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.binzberger@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 <le...@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 <ha...@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.
>>>>> * hans@confluent.io (650)924-2670
>>>>> */
>>>>>
>>>>> On Mon, Mar 6, 2017 at 5:37 AM, Le Cyberian <le...@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 <ha...@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 <je...@tink.se>
>>>>>>>>
>>>>>>> wrote:
>>>>>
>>>>>> Hi Hans,
>>>>>>>>
>>>>>>>> On Mon, Mar 6, 2017 at 12:10 AM, Hans Jespersen <ha...@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.rantil@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>
>>>>>>>>
>>>>>>>
>>>
>>
Re: Having 4 Node Kafka Cluster
Posted by Le Cyberian <le...@gmail.com>.
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.binzberger@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 <le...@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 <ha...@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.
>>>> * hans@confluent.io (650)924-2670
>>>> */
>>>>
>>>> On Mon, Mar 6, 2017 at 5:37 AM, Le Cyberian <le...@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 <ha...@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 <je...@tink.se>
>>>>>>>
>>>>>> wrote:
>>>>
>>>>> Hi Hans,
>>>>>>>
>>>>>>> On Mon, Mar 6, 2017 at 12:10 AM, Hans Jespersen <ha...@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.rantil@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>
>>>>>>>
>>>>>>
>>
>
Re: Having 4 Node Kafka Cluster
Posted by Alexander Binzberger <al...@wingcon.com>.
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\u2019s 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\u2019t 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 <le...@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 <ha...@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.
>>> * hans@confluent.io (650)924-2670
>>> */
>>>
>>> On Mon, Mar 6, 2017 at 5:37 AM, Le Cyberian <le...@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 <ha...@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 <je...@tink.se>
>>> wrote:
>>>>>> Hi Hans,
>>>>>>
>>>>>>> On Mon, Mar 6, 2017 at 12:10 AM, Hans Jespersen <ha...@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.rantil@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>
>
Re: Having 4 Node Kafka Cluster
Posted by Hans Jespersen <ha...@confluent.io>.
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 <le...@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 <ha...@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.
>> * hans@confluent.io (650)924-2670
>> */
>>
>> On Mon, Mar 6, 2017 at 5:37 AM, Le Cyberian <le...@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 <ha...@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 <je...@tink.se>
>> wrote:
>>>>>
>>>>> Hi Hans,
>>>>>
>>>>>> On Mon, Mar 6, 2017 at 12:10 AM, Hans Jespersen <ha...@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.rantil@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>
>>>>
>>>
>>
Re: Having 4 Node Kafka Cluster
Posted by Le Cyberian <le...@gmail.com>.
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 <ha...@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.
> * hans@confluent.io (650)924-2670
> */
>
> On Mon, Mar 6, 2017 at 5:37 AM, Le Cyberian <le...@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 <ha...@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 <je...@tink.se>
> wrote:
> > > >
> > > > Hi Hans,
> > > >
> > > >> On Mon, Mar 6, 2017 at 12:10 AM, Hans Jespersen <ha...@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.rantil@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>
> > >
> >
>
Re: Having 4 Node Kafka Cluster
Posted by Le Cyberian <le...@gmail.com>.
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.
I am confused somehow :-/ what to do in this case
BR,
Lee
On Mon, Mar 6, 2017 at 2:50 PM, Hans Jespersen <ha...@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.
> * hans@confluent.io (650)924-2670
> */
>
> On Mon, Mar 6, 2017 at 5:37 AM, Le Cyberian <le...@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 <ha...@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 <je...@tink.se>
> wrote:
> > > >
> > > > Hi Hans,
> > > >
> > > >> On Mon, Mar 6, 2017 at 12:10 AM, Hans Jespersen <ha...@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.rantil@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>
> > >
> >
>
Re: Having 4 Node Kafka Cluster
Posted by Hans Jespersen <ha...@confluent.io>.
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.
* hans@confluent.io (650)924-2670
*/
On Mon, Mar 6, 2017 at 5:37 AM, Le Cyberian <le...@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 <ha...@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 <je...@tink.se> wrote:
> > >
> > > Hi Hans,
> > >
> > >> On Mon, Mar 6, 2017 at 12:10 AM, Hans Jespersen <ha...@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.rantil@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>
> >
>
Re: Having 4 Node Kafka Cluster
Posted by Le Cyberian <le...@gmail.com>.
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 <ha...@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 <je...@tink.se> wrote:
> >
> > Hi Hans,
> >
> >> On Mon, Mar 6, 2017 at 12:10 AM, Hans Jespersen <ha...@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.rantil@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>
>
Re: Having 4 Node Kafka Cluster
Posted by Le Cyberian <le...@gmail.com>.
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 <ha...@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 <je...@tink.se> wrote:
> >
> > Hi Hans,
> >
> >> On Mon, Mar 6, 2017 at 12:10 AM, Hans Jespersen <ha...@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.rantil@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>
>
Re: Having 4 Node Kafka Cluster
Posted by Hans Jespersen <ha...@confluent.io>.
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 <je...@tink.se> wrote:
>
> Hi Hans,
>
>> On Mon, Mar 6, 2017 at 12:10 AM, Hans Jespersen <ha...@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.rantil@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>
Re: Having 4 Node Kafka Cluster
Posted by Jens Rantil <je...@tink.se>.
Hi Hans,
On Mon, Mar 6, 2017 at 12:10 AM, Hans Jespersen <ha...@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.rantil@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>
Re: Having 4 Node Kafka Cluster
Posted by Hans Jespersen <ha...@confluent.io>.
A 4 node zookeeper ensemble will not even work. It MUST be an odd number of zookeeper nodes to start.
For Kafka you can start with any number of nodes (including 4). Remember that it is the partitions that are replicated, not the entire broker so if you have a Kafka node crash, its only the partitions that were leaders on that node that need to move to the remaining brokers and they will try to be balanced across the remaining in-sync replicas on the remaining nodes.
-hans
Sent from my iPhone
> On Mar 5, 2017, at 1:46 PM, Le Cyberian <le...@gmail.com> wrote:
>
> Hi Guys,
>
> I have a scenario where i need to configure a 4 node Kafka Cluster along
> with Zookeeper having 4 nodes as well.
>
> I understand as a rule of them when it comes to cluster its always odd
> number, however this is the case i need to do it.
>
> For zookeeper, i understand with a 4 node cluster i can tolerate failure of
> 1 node which is same as having a 3 node cluster which does not give benefit
> of having 4th one. how does it effect when it comes to leader election ?
>
> For Kafka its the same case, I wanted to understand if we really want to do
> this and achieve fault tolerance some how.
>
> Thanks!
>
> Lee