Re: Improve the connection failure error messages

Thanks for the review. Attached v2 patch with suggested changes.
Please find my response inline.

On Fri, Jan 12, 2024 at 8:20 AM Peter Smith <smithpb2250(at)gmail(dot)com> wrote:
>
> Thanks for the patch! Here are a couple of review comments for it.
>
> ======
> src/backend/commands/subscriptioncmds.c
>
> 1.
> @@ -742,7 +742,7 @@ CreateSubscription(ParseState *pstate,
> CreateSubscriptionStmt *stmt,
> if (!wrconn)
> ereport(ERROR,
> (errcode(ERRCODE_CONNECTION_FAILURE),
> - errmsg("could not connect to the publisher: %s", err)));
> + errmsg("\"%s\" could not connect to the publisher: %s", stmt->subname, err)));
>
> In practice, these commands give errors like:
>
> test_sub=# create subscription sub1 connection 'dbname=bogus' publication pub1;
> ERROR: could not connect to the publisher: connection to server on
> socket "/tmp/.s.PGSQL.5432" failed: FATAL: database "bogus" does not
> exist
>
> and logs like:
>
> 2024-01-12 12:45:05.177 AEDT [13108] ERROR: could not connect to the
> publisher: connection to server on socket "/tmp/.s.PGSQL.5432" failed:
> FATAL: database "bogus" does not exist
> 2024-01-12 12:45:05.177 AEDT [13108] STATEMENT: create subscription
> sub1 connection 'dbname=bogus' publication pub1;
>
> Since the subscription name is already obvious from the statement that
> caused the error I'm not sure it benefits much to add this to the
> error message (but maybe it is useful if the error message was somehow
> read in isolation from the statement).
>
> Anyway, I felt at least it should include the word "subscription" for
> better consistency with the other messages in this patch:
>
> SUGGESTION
> subscription \"%s\" could not connect to the publisher: %s

Done.

> ======
>
> 2.
> + appname = cluster_name[0] ? cluster_name : "walreceiver";
> +
> /* Establish the connection to the primary for XLOG streaming */
> - wrconn = walrcv_connect(conninfo, false, false,
> - cluster_name[0] ? cluster_name : "walreceiver",
> - &err);
> + wrconn = walrcv_connect(conninfo, false, false, appname, &err);
> if (!wrconn)
> ereport(ERROR,
> (errcode(ERRCODE_CONNECTION_FAILURE),
> - errmsg("could not connect to the primary server: %s", err)));
> + errmsg("%s could not connect to the primary server: %s", appname, err)));
>
> I think your new %s should be quoted according to the guidelines at [1].

Done.

> ======
> src/test/regress/expected/subscription.out
>
> 3.
> Apparently, there is no existing regression test case for the ALTER
> "could not connect" message because if there was, it would have
> failed. Maybe a test should be added?
>
The ALTER SUBSCRIPTION command does not error out on the user
interface if updated with a bad connection string and the connection
failure error can only be seen in the respective log file.
Due to this behavior, it is not possible to add a test to show the
error message as it is done for CREATE SUBSCRIPTION.
Let me know if you think there is another way to add this test.

--
Thanks,
Nisha