Re: pg_stat_replication in 9.3

On 14/09/14 18:55, Tom Lane wrote:
> Are you watching the state in a loop inside a single plpgsql function?
> If so, I wonder whether the problem is that the plpgsql function's
> snapshot isn't changing. From memory, marking the function VOLATILE
> would help if that's the issue.

The function is VOLATILE. I attached 2 versions of it. fn-old.sql does
not work because once a slave has disconnected it drops out and does not
come back. fn.sql uses dblink to work around the problem. But it
consumes 2 db connections.

The intent of the function is to be called between operations that may
cause slaves to lag behind. If the lag is below a certain limit, it
simply returns. Otherwise, it waits until the lag drops below a second
limit.

If it were a VOLATILE problem, the functions would not be able to see
when a slave drops out nor changes in the data. But it does see these
changes. Only when a slave comes back online, it is not seen in the
current transaction.

Torsten