Horton

Re: Switching XLog source from archive to streaming when primary available

Kyotaro Horiguchi <horikyota.ntt@gmail.com>

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From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
To: bharath.rupireddyforpostgres@gmail.com
Cc: nathandbossart@gmail.com, cary.huang@highgo.ca, pgsql-hackers@lists.postgresql.org, satyanarlapuram@gmail.com
Date: 2022-09-16T06:36:29Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Add basic TAP tests for the low-level backup method, take two

  2. Add a failover option to subscriptions.

  3. Make all Perl warnings fatal

  4. Add PostgreSQL::Test::Cluster::advance_wal

  5. Rename wal_keep_segments to wal_keep_size.

At Fri, 16 Sep 2022 09:15:58 +0530, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com> wrote in 
> On Thu, Sep 15, 2022 at 1:52 PM Kyotaro Horiguchi
> <horikyota.ntt@gmail.com> wrote:
> >
> > At Thu, 15 Sep 2022 10:28:12 +0530, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com> wrote in
> > > I'm attaching the v6 patch that's rebased on to the latest HEAD.
> > > Please consider this for review.
> >
> > Thaks for the new version!
> >
> > +#define StreamingReplRetryEnabled() \
> > +       (streaming_replication_retry_interval > 0 && \
> > +        StandbyMode && \
> > +        currentSource == XLOG_FROM_ARCHIVE)
> >
> > It seems to me a bit too complex..

In other words, it seems to me that the macro name doesn't manifest
the condition correctly.

> I don't think so, it just tells whether a standby is allowed to switch
> source to stream from archive.
> 
> > +                       /* Save the timestamp at which we're switching to archive. */
> > +                       if (StreamingReplRetryEnabled())
> > +                               switched_to_archive_at = GetCurrentTimestamp();
> >
> > Anyway we are going to open a file just after this so
> > GetCurrentTimestamp() cannot cause a perceptible degradation.
> > Coulnd't we do that unconditionally, to get rid of the macro?
> 
> Do we really need to do it unconditionally? I don't think so. And, we
> can't get rid of the macro, as we need to check for the current
> source, GUC and standby mode. When this feature is disabled, it
> mustn't execute any extra code IMO.

I don't think we don't particularly want to do that unconditionally.
I wanted just to get rid of the macro from the usage site.  Even if
the same condition is used elsewhere, I see it better to write out the
condition directly there..

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center