Re: warning message in standby

On Tue, Jun 15, 2010 at 12:09 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> The testing that I have been doing while we've been discussing this
> reveals that you are correct.  I set up an HS/SR master and slave
> (running on the same machine), ran pgbench on the master, and then
> started randomly sending SIGSEGV to one of the master's backends.  It
> seems that complaints about the WAL are possible on both master and
> slave.  Here are a couple from the slave:
>
> LOG:  unexpected pageaddr 0/89B7A000 in log file 0, segment 152, offset 12034048
> WARNING:  there is no contrecord flag in log file 0, segment 136, offset 2523136
> LOG:  invalid magic number 0000 in log file 0, segment 136, offset 2531328
>
> The slave reconnects and then things get better.  So I think your idea
> of retrying once and then panicking is probably best.

AFAIR, in the previous discussion, some people think that it's better to
keep the standby open for read-only queries even if an error is found.
Panicking would be undesirable for them.

On the other hand, I like immediate-panicking. And I don't want the standby
to retry reconnecting the master infinitely.

To cover all the use cases, how about introducing new parameter specifying
the maximum number of times to retry reconnecting? If we like the retry-once-
then-panicking idea, we can set the parameter to one. If we'd like to keep
the standby open infinitely, we can set it to the very large value (or -1
meaning infinite retrying). If we think that immediate-panicking is the best,
we can set it to zero. Thought?

Regards,

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center