Re: Synchronous Replication Timeout

[Sameer Kumar <sameer.kumar@xxxxxxxxxx>]

On Fri, Nov 28, 2014 at 10:24 AM, Teresa Bradbury <TB@xxxxxxxxxxxxxxxxxxxx> wrote:

I have a replication setup with a master and a single synchronous slave. If the slave dies (or the network goes down) I would like any transaction on the master that requires writing to fail so I can roll it back. At the moment, when I commit it just hangs forever or (if I cancel it using ^C in psql or using kill) it commits locally and not on the synchronous slave.

​I did that for a customer and I am using a tool (pgpool) to change the config file if the master is going down. You can keep additional configurations in

synchronous_master.conf and add include header in postgresql.conf

You just need to write a shell script (or use something like pgpool)​ to keep a watch if the slave goes down change synchronous_master.conf to an empty file and reload the postgres config (pg_ctl reload).

 

Neither of these options are ok in my use case. I have tried setting statement_timeout but it does not work. So my questions are:

 

1) Is it possible to rollback transactions that fail to commit after a certain amount of time waiting for the slave?

​No, AFAIK it would have already committed to WAL files on on master.​

 

​It is just blocked till the slave confirms the ​same being done at its end.

 

2) If not, is there any intension of implementing such a feature in the near future?

 

3) Do any of the answers above change if we are dealing with two-phase commits instead? At the moment it hangs forever on ‘prepare transaction’, ‘commit prepared’ and ‘rollback prepared’ commands.

Best Regards,

Sameer Kumar | Database Consultant

ASHNIK PTE. LTD.

101 Cecil Street, #11-11 Tong Eng Building, Singapore 069533

M: +65 8110 0350  T: +65 6438 3504 | www.ashnik.com

 

 

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