On 09/29/2014 01:13 PM, furu...@pm.nttdata.co.jp wrote:
I don't understand what this patch does. When would you want to use
the new --reply-fsync option? Is there any reason *not* to use it?
In other words, do we need an option for this, couldn't you just
always send the feedback message after fsync?
Thanks for the comment.
--reply-fsync option is intended for use in synchronous mode.
By specifying -F option and --slot option, process calls fsync() when
it received the WAL, and flush location would be set in feedback
message.
Interval of sending feedback message depends on -s option in this
state, so in the case of synchronous mode, waiting for feedback
message would occure.
therefore, --reply-fsync option is necessary. because it can send the
feedback message after fsync without waiting for the interval of -s
option.
The reason for not sending the feedback message after fsync without
waiting for the interval of -s option always, is to answer the needs
who want to use fsync only (NOT using synchronous mode).
I still don't get it. AFAICS there are two ways to use pg_receivexlog.
Either you use it as a synchronous standby, or not.
What set of options would you pass if you want to use it as a
synchronous standby? And if you don't? Could we just have a single
"--synchronous" flag, instead of -F and --reply-fsync?
- Heikki
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