Re: Improve error handling for invalid slots and ensure a same 'inactive_since' time for inactive slots

On Wed, Jan 29, 2025 at 8:55 AM Peter Smith <smithpb2250(at)gmail(dot)com> wrote:
>
> ======
> src/backend/replication/slot.c
>
> 1.
> +
> +/*
> + * Raise an error based on the slot's invalidation cause.
> + */
> +static void
> +RaiseSlotInvalidationError(ReplicationSlot *slot)
> +{
> + StringInfo err_detail = makeStringInfo();
> +
> + Assert(slot->data.invalidated != RS_INVAL_NONE);
> +
> + switch (slot->data.invalidated)
> + {
> + case RS_INVAL_WAL_REMOVED:
> + appendStringInfoString(err_detail, _("This slot has been invalidated
> because the required WAL has been removed."));
> + break;
> +
> + case RS_INVAL_HORIZON:
> + appendStringInfoString(err_detail, _("This slot has been invalidated
> because the required rows have been removed."));
> + break;
> +
> + case RS_INVAL_WAL_LEVEL:
> + /* translator: %s is a GUC variable name */
> + appendStringInfo(err_detail, _("This slot has been invalidated
> because \"%s\" is insufficient for slot."),
> + "wal_level");
> + break;
> +
> + case RS_INVAL_NONE:
> + pg_unreachable();
> + }
> +
> + ereport(ERROR,
> + errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
> + errmsg("can no longer get changes from replication slot \"%s\"",
> + NameStr(slot->data.name)),
> + errdetail_internal("%s", err_detail->data));
> +}
>
> AFAIK the _() is a macro for gettext(). So those strings are intended
> for translation, right? There's also a "/* translator: ..." comment
> implying the same.
>
> OTOH, those strings are only being used by errdetail_internal, whose
> function comment says "This is exactly like errdetail() except that
> strings passed to errdetail_internal are not translated...".
>
> Isn't there some contradiction here?
>

Yeah, I also think so but I see some other similar usages. For
example, parse_one_reloption() uses errdetail_internal("%s",
_(optenum->detailmsg)) : 0));

There are various other places in the code where _( is used for
messages in errmsg_internal.

> Perhaps the _() macro is not needed, or perhaps the
> errdetail_internal() should be errdetail().
>

These messages should be with errdetail. We already have these
messages being displayed as errdetail in CreateDecodingContext().
Also, after this patch, shouldn't we remove the same error cases in
CreateDecodingContext(). There is already an
Assert(MyReplicationSlot->data.invalidated == RS_INVAL_NONE) which
should be sufficient after this patch to ensure we didn't miss any
error cases.

--
With Regards,
Amit Kapila.