Re: Why there are no max_wal_receivers

Hi,

On Mon, Oct 7, 2013 at 12:02 PM, 高健 <luckyjackgao(at)gmail(dot)com> wrote:
> Hello :
>
>
> I found that for PG9.2.4, there is parameter max_wal_senders,
>
> But there is no parameter of max_wal_receivers.
>
>

max_wal_senders is the maximum number of WAL sender processes that a
primary server can create in response to requests from the standby
servers. One WAL sender process is created on the primary server for
each standby which would running the corresponding WAL receiver. So
there is one-to-one mapping between WAL senders and WAL receivers
(standbys).

>
> Is that to say, that If max_wal_senders are 3.
>
> Then 3 wal_senders will be activated ,
>
>
>
> And then on the standby server, there will be 3 "receivers" for counter-part
> ?
>

max_wal_senders=3 means, there can be maximum 3 standby servers
requesting primary to send the WAL.
So, while the primary server may be running multiple WAL senders,
there is only one WAL receiver on each standby server.

--
Amit Langote