Re: Support for N synchronous standby servers - take 2

On 16 July 2015 at 18:27, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

> On Wed, Jul 15, 2015 at 5:03 AM, Michael Paquier
> <michael(dot)paquier(at)gmail(dot)com> wrote:
> >> Group labels are essential.
> >
> > OK, so this is leading us to the following points:
> > - Use a JSON object to define the quorum/priority groups for the sync
> state.
> > - Store it as a GUC, and use the check hook to validate its format,
> > which is what we have now with s_s_names
> > - Rely on SIGHUP to maintain an in-memory image of the quorum/priority
> > sync state
> > - Have the possibility to define group labels in this JSON blob, and
> > be able to use those labels in a quorum or priority sync definition.
> > - For backward-compatibility, use for example s_s_names = 'json' to
> > switch to the new system.
>
> Personally, I think we're going to find that using JSON for this
> rather than a custom syntax makes the configuration strings two or
> three times as long for

They may well be 2-3 times as long. Why is that a negative?

> no discernable benefit.
>

Benefits:
* More readable
* Easy to validate
* No additional code required in the server to support this syntax (so no
bugs)
* Developers will immediately understand the format
* Easy to programmatically manipulate in a range of languages

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