Re: How to Identify and Fail Transaction When Slave Node Down

On 2017-03-16 10:06, Anushka Weerakkodyge wrote:
> Hi,
>
> problem still persists.
> Is there any configuration (parameter?) to set the timeout of the
> connection ? Because if the slave node is down, transaction to master
> node waits forever until slave node comes back online.
> Any suggestion would be highly appreciated.
>
> Thanks,
> Anushka
> On Thu, Mar 16, 2017 at 5:21 AM, Anushka Weerakkodyge
> <anushkaw(at)ceylonit(dot)com> wrote:
>
>> Hi all,
>>
>> I have a synchronous streaming replication environment which is
>> implemented using inbuilt replication mechanism in postgresql.
>> Replication is working fine except I need to fail the data
>> modification transactions when the slave node is not accessible.
>>
>> Is it possible?
>>
>> Please let me know whether there is a way to identify slave node
>> status and fail the transaction using any inbuilt mechanism or some
>> other technique.
>>
>> Thanks,
>> Anushka

As far as I know, which is does not mean much, there is no timeout
setting.
And that's by design; a timeout can occur because the node is down,
but also because it's busy and cannot answer in time, or there is a
network hickup.

Adding a timeout would basically break the "syncronous" promise
because that guarantees that either all nodes are updated, or the
transaction fails.

And yes I googled this from:
https://www.postgresql.org/message-id/CADp-Sm7ENFJH4YQmJVYD2qB2OaKa6qb6TEHCJWfce%2BQoQXsdhA%40mail.gmail.com

In the case of a node going down you should probably but some failover
mechanism in place so you can safely remove the dead node from the setup
and rebuild it before making it part of the cluster again.