Re: Add errdetail() with PID and UID about source of termination signal - Mailing list pgsql-hackers

> On Feb 25, 2026, at 16:26, Jakub Wartak <jakub.wartak@enterprisedb.com> wrote:
>
> On Tue, Feb 24, 2026 at 5:15 PM Andrew Dunstan <andrew@dunslane.net> wrote:
>>
>>
>> On 2026-02-24 Tu 5:05 AM, Jakub Wartak wrote:
>>> On Tue, Feb 24, 2026 at 9:40 AM Chao Li <li.evan.chao@gmail.com> wrote:
>>> [..]
>>>
>>>> There is guidance in the documentation regarding error message style:
https://www.postgresql.org/docs/current/error-style-guide.html
>>>> ```
>>>> Detail and hint messages: Use complete sentences, and end each with a period. Capitalize the first word of
sentences.Put two spaces after the period if another sentence follows (for English text; might be inappropriate in
otherlanguages). 
>>>> ```
>>>>
>>>> I also noticed that some existing DETAIL and HINT messages do not fully follow this guideline. But I believe new
codeshould adhere to the documented style as much as possible. In particular, DETAIL and HINT messages should begin
witha capital letter and follow the complete-sentence convention. 
>>> Hi, v2 attached, WIP, the only known remaining issue to me is that
>>> windows might fail to compile as it probably doesn't have concept of
>>> uid_t... I'm wondering what to do there.
>>
>>
>> I don't think it will arise, as Windows doesn't have the siginfo stuff,
>> AFAIK.
>>
>
> Hi Andrew. Ok, so V3 is attached with just one change: uid_t/pid_t
> changed to uint32 to make win32 happy.
>
> Perhaps one question is whether this should be toggleable with GUC or not.
>
> -J.
> <v3-0001-Add-errdetail-with-PID-and-UID-about-source-of-te.patch>

A few comments for v3:

1 - syncrep.c
```
@@ -302,7 +302,11 @@ SyncRepWaitForLSN(XLogRecPtr lsn, bool commit)
             ereport(WARNING,
                     (errcode(ERRCODE_ADMIN_SHUTDOWN),
                      errmsg("canceling the wait for synchronous replication and terminating connection due to
administratorcommand"), 
-                     errdetail("The transaction has already committed locally, but might not have been replicated to
thestandby."))); 
+                     errdetail("The transaction has already committed locally, but might not have been replicated to
thestandby."), 
+                        proc_die_sender_pid == 0 ? 0 :
+                            errdetail("Signal sent by PID %lld, UID %lld.",
+                                (long long)proc_die_sender_pid, (long long)proc_die_sender_uid)
+                        ));
```

Here errdetail is used twice. I guess the second conditional one should be errhint.

2 - syncrep.c
```
-                     errdetail("The transaction has already committed locally, but might not have been replicated to
thestandby."))); 
+                     errdetail("The transaction has already committed locally, but might not have been replicated to
thestandby."), 
+                        proc_die_sender_pid == 0 ? 0 :
+                            errdetail("Signal sent by PID %lld, UID %lld.",
+                                (long long)proc_die_sender_pid, (long long)proc_die_sender_uid)
+                        ));
```

Same as comment 1.

3
```
+volatile uint32 proc_die_sender_pid = 0;
+volatile uint32 proc_die_sender_uid = 0;
```

These two globals are only written in the signal handler, I think they should be sig_atomic_t to ensure atomic writes.

4
```
-                     errmsg("terminating walreceiver process due to administrator command")));
+                     errmsg("terminating walreceiver process due to administrator command"),
+                     proc_die_sender_pid == 0 ? 0 :
+                        errdetail("Signal sent by PID %lld, UID %lld.",
+                            (long long)proc_die_sender_pid, (long long)proc_die_sender_uid)
+                    ));
```

Why do we need to format pid and uid in “long long” format? I searched over the source tree, the current postmaster.c
justformats pid as int (%d): 
```
    /* in parent, successful fork */
    ereport(DEBUG2,
            (errmsg_internal("forked new %s, pid=%d socket=%d",
                             GetBackendTypeDesc(bn->bkend_type),
                             (int) pid, (int) client_sock->sock)));
```

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/