Usage of myId

[Avinash Lakshman <av...@gmail.com>]

Why is this important? What breaks down if I have 2 servers with the same
myId?

Cheers
A

Re: Usage of myId

[Patrick Hunt <ph...@apache.org>]

re previous discussion see this thread: 
http://www.mail-archive.com/zookeeper-user@hadoop.apache.org/msg00916.html

Patrick

Nick Dimiduk wrote:
> I think automating this assignment has been discussed in the past. IIRC,
> some combination of MAC address and pid or timestamp would be sufficient to
> uniquely identify a ZK instance. There may be some detail I'm forgetting
> about maintaining the ID between process restarts, making these ephemeral
> values unacceptable.
> 
> Cheers,
> -Nick
> 
> On Mon, Mar 1, 2010 at 6:56 PM, Henry Robinson <he...@cloudera.com> wrote:
> 
>> If you have two servers with the same myid, two servers will identify
>> themselves as the 'same' machine X in a ZooKeeper ensemble. This id is used
>> to map onto a hostname / port pair where messages for a given server are
>> sent. Assuming a consistent quorum specification across all machines,
>> messages for server X will only go to one machine and the other will think
>> itself partitioned from the network.
>>
>> Servers need ids to distinguish themselves from other servers in order to
>> break symmetry and successfully elect a leader.
>>
>> Henry
>>
>> On 27 February 2010 23:06, Qian Ye <ye...@gmail.com> wrote:
>>
>>> myid is used to identify your service instance, with its help, it is
>>> possible to start more than one Zookeeper service on one computer. If the
>>> configuration of myid is wrong, the service can not be started properly.
>>>
>>> On Sun, Feb 28, 2010 at 11:39 AM, Avinash Lakshman <
>>> avinash.lakshman@gmail.com> wrote:
>>>
>>>> Why is this important? What breaks down if I have 2 servers with the
>> same
>>>> myId?
>>>>
>>>> Cheers
>>>> A
>>>>
>>>
>>>
>>> --
>>> With Regards!
>>>
>>> Ye, Qian
>>>
>>
>>
>> --
>> Henry Robinson
>> Software Engineer
>> Cloudera
>> 415-994-6679
>>
> 

Re: Usage of myId

[Nick Dimiduk <nd...@gmail.com>]

I think automating this assignment has been discussed in the past. IIRC,
some combination of MAC address and pid or timestamp would be sufficient to
uniquely identify a ZK instance. There may be some detail I'm forgetting
about maintaining the ID between process restarts, making these ephemeral
values unacceptable.

Cheers,
-Nick

On Mon, Mar 1, 2010 at 6:56 PM, Henry Robinson <he...@cloudera.com> wrote:

> If you have two servers with the same myid, two servers will identify
> themselves as the 'same' machine X in a ZooKeeper ensemble. This id is used
> to map onto a hostname / port pair where messages for a given server are
> sent. Assuming a consistent quorum specification across all machines,
> messages for server X will only go to one machine and the other will think
> itself partitioned from the network.
>
> Servers need ids to distinguish themselves from other servers in order to
> break symmetry and successfully elect a leader.
>
> Henry
>
> On 27 February 2010 23:06, Qian Ye <ye...@gmail.com> wrote:
>
> > myid is used to identify your service instance, with its help, it is
> > possible to start more than one Zookeeper service on one computer. If the
> > configuration of myid is wrong, the service can not be started properly.
> >
> > On Sun, Feb 28, 2010 at 11:39 AM, Avinash Lakshman <
> > avinash.lakshman@gmail.com> wrote:
> >
> > > Why is this important? What breaks down if I have 2 servers with the
> same
> > > myId?
> > >
> > > Cheers
> > > A
> > >
> >
> >
> >
> > --
> > With Regards!
> >
> > Ye, Qian
> >
>
>
>
> --
> Henry Robinson
> Software Engineer
> Cloudera
> 415-994-6679
>

Re: Usage of myId

[Henry Robinson <he...@cloudera.com>]

If you have two servers with the same myid, two servers will identify
themselves as the 'same' machine X in a ZooKeeper ensemble. This id is used
to map onto a hostname / port pair where messages for a given server are
sent. Assuming a consistent quorum specification across all machines,
messages for server X will only go to one machine and the other will think
itself partitioned from the network.

Servers need ids to distinguish themselves from other servers in order to
break symmetry and successfully elect a leader.

Henry

On 27 February 2010 23:06, Qian Ye <ye...@gmail.com> wrote:

> myid is used to identify your service instance, with its help, it is
> possible to start more than one Zookeeper service on one computer. If the
> configuration of myid is wrong, the service can not be started properly.
>
> On Sun, Feb 28, 2010 at 11:39 AM, Avinash Lakshman <
> avinash.lakshman@gmail.com> wrote:
>
> > Why is this important? What breaks down if I have 2 servers with the same
> > myId?
> >
> > Cheers
> > A
> >
>
>
>
> --
> With Regards!
>
> Ye, Qian
>



-- 
Henry Robinson
Software Engineer
Cloudera
415-994-6679

Re: Usage of myId

[Qian Ye <ye...@gmail.com>]

myid is used to identify your service instance, with its help, it is
possible to start more than one Zookeeper service on one computer. If the
configuration of myid is wrong, the service can not be started properly.

On Sun, Feb 28, 2010 at 11:39 AM, Avinash Lakshman <
avinash.lakshman@gmail.com> wrote:

> Why is this important? What breaks down if I have 2 servers with the same
> myId?
>
> Cheers
> A
>



-- 
With Regards!

Ye, Qian