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Subject: Re: Leader election problems
From: Filip Deleersnijder <filip@motum.be>
In-Reply-To: 
 <CAMUR=WjxUaXbMD8tz07On_tGOdzYyK+0D4Dj93bd6+rf66wvEA@mail.gmail.com>
Date: Thu, 25 Jun 2015 08:39:56 +0200
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Message-Id: <24927B98-DABB-4D6D-8BCB-9F8D60896EAC@motum.be>
References: <0ABDD99C-B3C1-4278-B6E8-6A997658B988@motum.be>
 <CAMUR=WjxUaXbMD8tz07On_tGOdzYyK+0D4Dj93bd6+rf66wvEA@mail.gmail.com>
To: user@zookeeper.apache.org

Hi,

Thanks for your response.

Our application consists of 8 automatic vehicles in a warehouse setting. =
Those vehicles need some consensus decisions, and that is what we use =
Zookeeper for.
Because vehicles can come and go at random, we installed a ZK =
participant on every vehicle. The ZK client is some other piece of =
software that is also running on the vehicles.

Therefor :=20
	- We can not choose the number of ZK-participants because it =
just depends on the number of vehicles.
	- The participants communicate over Wifi
	- The client is running on the same machine, so it communicates =
over the local network

We are running Zookeeper version 3.4.6

Our zoo.cfg can be found below this e-mail.

Thanks in advance !

Filip

# The number of milliseconds of each tick
tickTime=3D2000
# The number of ticks that the initial=20
# synchronization phase can take
initLimit=3D10
# The number of ticks that can pass between=20
# sending a request and getting an acknowledgement
syncLimit=3D5
# the directory where the snapshot is stored.
# do not use /tmp for storage, /tmp here is just=20
# example sakes.
dataDir=3Dc:/motum/config/MASS/ZK
# the port at which the clients will connect
clientPort=3D2181

server.1=3D172.17.35.11:2888:3888
server.2=3D172.17.35.12:2888:3888
server.3=3D172.17.35.13:2888:3888
server.4=3D172.17.35.14:2888:3888
server.5=3D172.17.35.15:2888:3888
server.6=3D172.17.35.16:2888:3888
server.7=3D172.17.35.17:2888:3888
server.8=3D172.17.35.18:2888:3888

# The number of snapshots to retain in dataDir
# Purge task interval in hours
# Set to "0" to disable auto purge feature
autopurge.snapRetainCount=3D3
autopurge.purgeInterval=3D1


> On 24 Jun 2015, at 18:54, Ra=C3=BAl Guti=C3=A9rrez Segal=C3=A9s =
<rgs@itevenworks.net> wrote:
>=20
> Hi,
>=20
> On 24 June 2015 at 06:05, Filip Deleersnijder <filip@motum.be> wrote:
>=20
>> Hi,
>>=20
>> Let=E2=80=99s start with some description of our system :
>>=20
>> - We our using a Zookeeper cluster with 8 participants for an =
application
>> with mobile nodes ( connected over Wifi ).
>>=20
>=20
> You mean the participants talk over wifi or the clients?
>=20
>=20
>> ( Ip of the different nodes are according to the following structure =
:
>> Node X has IP : 172.17.35.1X )
>>=20
>=20
> Why 8 and not an odd number of machines (i.e.:
> =
http://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_zkMulitServer=
Setup
> )?
>=20
> - It is not that unusual to have a node being shut-down or restarted
>> - We haven=E2=80=99t benchmarked the number of write operations yet, =
but I would
>> estimate that it would be less than 10 writes / second
>>=20
>=20
> What version of ZK are you using?
>=20
>=20
>>=20
>> The problem we are having however is that sometimes(*), some =
instances
>> seem to be having problems with leader election.
>> Under the header =E2=80=9CAttachment 1=E2=80=9D below, you can find =
the leader election
>> times that were needed over 24h ( from 1 node ).  One average it took =
more
>> than 1 minute !
>> I assume that this is not normal behaviour ? ( If somebody could =
confirm
>> that in a 8-node cluster, these are not normal leader election times, =
that
>> would be nice )
>>=20
>> In attachement 2 : I included an extract from the logging during a =
leader
>> election that took 101874ms for 1 node ( server 2 ).
>>=20
>> Any help is greatly appreciated.
>> If further or more specific logging is required, please ask !
>>=20
>>=20
> Do you mind sharing a copy of your config file (zoo.cfg)? Thanks!
>=20
>=20
> -rgs