Re: [Postgres-xc-general] Split brain

[Koichi S. <koi...@gm...>]

In this case, even though each node can access to GTM, update
transaction fails. If a transaction is involved by an unreachable
node, such local update fails, and then global update fails.  This
maintains cluster-wide database consistency.   Naturally, if a
transaction is involved only by reachable nodes, such transaction
succeeds and maintains cluster-wide consistency too.

Serious split bran case is: if you run two different GTM at the same
time and try to connect different coordinators to different GTMs.   As
in the case of almost other case, as Nikhil pointed out, this should
be resolved by some external tools.
----------
Koichi Suzuki


2013/3/19 Nikhil Sontakke <ni...@st...>:
> Hi Chris,
>
> Split brain is not solved internally by Postgres-XC. It's the job of
> an external layer to ensure that such scenarios do not occur.
>
> For example, one can use Corosync/Pacemaker to monitor XC nodes and
> then use proper mechanisms to ensure failover and STONITH steps. CS/PM
> solve the tricky problem of node membership and consistent cluster
> view pretty well.
>
> Regards,
> Nikhils
>
> On Tue, Mar 19, 2013 at 2:16 AM, Chris Brown <cb...@in...> wrote:
>> Hi all,
>>
>> I just read through:
>>
>> wiki.postgresql.org/images/4/44/Pgxc_HA_20121024.pdf
>>
>> and I wanted to know how PG-XC solves the problem of split brain.
>>
>> For example, let's say there is a pair:
>>   Box 1: datanode1-master, datanode2-slave, coordinator master, gtm master
>>   Box 2: datanode1-slave, datanode2-master, coordinator slave, gtm slave
>> and communication is severed between the two boxes.
>>
>> Another example:
>>   Box 1: datanode1-master, datanode2-slave, coordinator master, gtm proxy
>>   Box 2: datanode1-slave, datanode2-master, coordinator slave, gtm proxy
>>   Box 3: gtm (no slave exists for simplicity)
>> and communication is severed between box 1 and 2, but both can still
>> communicate with box 3.  (Or another network outage scenario - there are
>> obviously several.)
>>
>> Chris...
>>
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>
>
>
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