On Wed, 16 Jul 2025 at 21:30, Fujii Masao <masao.fu...@oss.nttdata.com> wrote:
>
>
>
> On 2025/07/16 19:45, vignesh C wrote:
> > If we don't trim the trailing newline, an extra blank line will appear
> > after the message is printed, like this:
> > 2025-07-16 12:44:20.076 IST [534376] LOG: logical replication table
> > synchronization worker for subscription "sub1", table "t2" has started
> > 2025-07-16 12:44:20.294 IST [534374] LOG: received message via
> > replication: WARNING: could not remove directory
> > "pg_replslot/pg_16396_sync_16384_7527574647116269356.tmp"
> >
> > 2025-07-16 12:44:20.294 IST [534374] LOG: logical replication table
> > synchronization worker for subscription "sub1", table "t1" has
> > finished
> >
> > This occurs because a newline is appended to the message in
> > pqBuildErrorMessage3, which is called when the message is received in
> > pqGetErrorNotice3:
> > ...
> > }
> > appendPQExpBufferChar(msg, '\n');
> > if (verbosity != PQERRORS_TERSE)
> > ...
>
> You're right, the message text passed to the notice processor includes
> a trailing newline. I confirmed this is documented in the PQsetNoticeProcessor
> docs [1], so I agree it's reasonable to trim the newline for cleaner log
> output.
>
>
> Regarding the current implementation:
> + /* Trim trailing newline for cleaner logs */
> + size_t len = strlen(message);
> +
> + if (len > 0 && message[len - 1] == '\n')
> + ereport(LOG,
> + errmsg("received message via replication:
> %.*s",
> + (int) (len - 1), message));
> + else
> + ereport(LOG,
> + errmsg("received message via replication:
> %s", message));
>
> To avoid repeating ereport(), how about refactoring it like this?
> I think it's simpler and easier to read:
>
> ---------------------------------------
> /*
> * Custom notice processor for replication connection.
> */
> static void
> notice_processor(void *arg, const char *message)
> {
> int len;
>
> /*
> * Trim the trailing newline from the message text passed to the
> notice
> * processor, as it always includes one, to produce cleaner log
> output.
> */
> len = strlen(message);
> if (len > 0 && message[len - 1] == '\n')
> len--;
>
> ereport(LOG,
> errmsg("received message via replication: %.*s",
> len, message));
> }
> ---------------------------------------
Looks good, modified
> Also, I suggest adding the prototype for notice_processor() in
> libpqwalreceiver.c:
>
> ---------------------------------------
> /* Prototypes for private functions */
> static void notice_processor(void *arg, const char *message);
> static char *stringlist_to_identifierstr(PGconn *conn, List *strings);
> ---------------------------------------
>
>
> Currently, notice_processor() is placed just before libpqrcv_connect(),
> but I think it would be better to move it before
> stringlist_to_identifierstr(),
> since the libpqwalreceiver.c seems to follow a structure where private
> functions come after the libpqrcv_* functions.
Modified
>
> + PQsetNoticeProcessor(conn->streamConn, notice_processor, NULL);
>
> It might be helpful to add a comment explaining the purpose, such as:
>
> Set a custom notice processor so that notice, warning, and similar
> messages
> received via the replication connection are logged in our preferred
> style,
> instead of just being printed to stderr.
Modified
The attached v4 version patch has the changes for the same.
Regards,
Vignesh
From 2460fbd0a5c6a1be425cdaf92daa2800407e4fcb Mon Sep 17 00:00:00 2001
From: Vignesh C <vignes...@gmail.com>
Date: Wed, 16 Jul 2025 15:26:12 +0530
Subject: [PATCH v4 1/3] Add custom PQsetNoticeProcessor handlers for
replication connection
This patch introduces a custom notice processor for libpq-based
connections in replication connection. The notice processor captures
messages and routes them through ereport(), making them visible in
local logs with a prefix making it easy for diagnosis.
---
.../libpqwalreceiver/libpqwalreceiver.c | 28 +++++++++++++++++++
1 file changed, 28 insertions(+)
diff --git a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
index f7b5d093681..689333d7c52 100644
--- a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
+++ b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
@@ -114,6 +114,7 @@ static WalReceiverFunctionsType PQWalReceiverFunctions = {
};
/* Prototypes for private functions */
+static void notice_processor(void *arg, const char *message);
static char *stringlist_to_identifierstr(PGconn *conn, List *strings);
/*
@@ -232,6 +233,13 @@ libpqrcv_connect(const char *conninfo, bool replication, bool logical,
errhint("Target server's authentication method must be changed, or set password_required=false in the subscription parameters.")));
}
+ /*
+ * Set a custom notice processor so that NOTICEs, WARNINGs, and similar
+ * messages from the replication connection are reported via ereport(),
+ * instead of being printed to stderr.
+ */
+ PQsetNoticeProcessor(conn->streamConn, notice_processor, NULL);
+
/*
* Set always-secure search path for the cases where the connection is
* used to run SQL queries, so malicious users can't get control.
@@ -1195,6 +1203,26 @@ libpqrcv_exec(WalReceiverConn *conn, const char *query,
return walres;
}
+/*
+ * Custom notice processor for replication connection.
+ */
+static void
+notice_processor(void *arg, const char *message)
+{
+ int len;
+
+ /*
+ * Trim the trailing newline from the message text passed to the notice
+ * processor, as it always includes one, to produce cleaner log output.
+ */
+ len = strlen(message);
+ if (len > 0 && message[len - 1] == '\n')
+ len--;
+
+ ereport(LOG,
+ errmsg("received message via replication: %.*s", len, message));
+}
+
/*
* Given a List of strings, return it as single comma separated
* string, quoting identifiers as needed.
--
2.43.0
From 9a0c0ce671d3860f1611c4ca1ec7cf55ab43e6e4 Mon Sep 17 00:00:00 2001
From: Vignesh C <vignes...@gmail.com>
Date: Wed, 16 Jul 2025 15:31:54 +0530
Subject: [PATCH v4 2/3] Add custom PQsetNoticeProcessor handlers for dblink
connection
This patch introduces a custom notice processor for libpq-based
connections in dblink connection. The notice processor captures
messages and routes them through ereport(), making them visible
in local logs with a prefix making it easy for diagnosis.
---
contrib/dblink/dblink.c | 31 +++++++++++++++++++++++++++++++
1 file changed, 31 insertions(+)
diff --git a/contrib/dblink/dblink.c b/contrib/dblink/dblink.c
index 8a0b112a7ff..30509f9ff32 100644
--- a/contrib/dblink/dblink.c
+++ b/contrib/dblink/dblink.c
@@ -137,6 +137,7 @@ static void appendSCRAMKeysInfo(StringInfo buf);
static bool is_valid_dblink_fdw_option(const PQconninfoOption *options, const char *option,
Oid context);
static bool dblink_connstr_has_required_scram_options(const char *connstr);
+static void notice_processor(void *arg, const char *message);
/* Global */
static remoteConn *pconn = NULL;
@@ -240,6 +241,14 @@ dblink_get_conn(char *conname_or_str,
errmsg("could not establish connection"),
errdetail_internal("%s", msg)));
}
+
+ /*
+ * Set a custom notice processor so that NOTICEs, WARNINGs, and
+ * similar messages from the remote server connection are reported via
+ * ereport(), instead of being printed to stderr.
+ */
+ PQsetNoticeProcessor(conn, notice_processor, NULL);
+
dblink_security_check(conn, NULL, connstr);
if (PQclientEncoding(conn) != GetDatabaseEncoding())
PQsetClientEncoding(conn, GetDatabaseEncodingName());
@@ -338,6 +347,8 @@ dblink_connect(PG_FUNCTION_ARGS)
errdetail_internal("%s", msg)));
}
+ PQsetNoticeProcessor(conn, notice_processor, NULL);
+
/* check password actually used if not superuser */
dblink_security_check(conn, connname, connstr);
@@ -2670,6 +2681,26 @@ dblink_connstr_has_required_scram_options(const char *connstr)
return (has_scram_keys && has_require_auth);
}
+/*
+ * Custom notice processor for remote server connection.
+ */
+static void
+notice_processor(void *arg, const char *message)
+{
+ int len;
+
+ /*
+ * Trim the trailing newline from the message text passed to the notice
+ * processor, as it always includes one, to produce cleaner log output.
+ */
+ len = strlen(message);
+ if (len > 0 && message[len - 1] == '\n')
+ len--;
+
+ ereport(LOG,
+ errmsg("received message from remote server: %.*s", len, message));
+}
+
/*
* We need to make sure that the connection made used credentials
* which were provided by the user, so check what credentials were
--
2.43.0
From 880d19658fdc3f9d4e31b1e6f1be670e1cb3dd46 Mon Sep 17 00:00:00 2001
From: Vignesh C <vignes...@gmail.com>
Date: Wed, 16 Jul 2025 15:32:41 +0530
Subject: [PATCH v4 3/3] Add custom PQsetNoticeProcessor handlers for fdw
connection
This patch introduces a custom notice processor for libpq-based
connections in fdw connection. The notice processor captures
messages and routes them through ereport(), making them visible
in local logs with a prefix making it easy for diagnosis.
---
contrib/postgres_fdw/connection.c | 27 +++++++++++++++++++++++++++
1 file changed, 27 insertions(+)
diff --git a/contrib/postgres_fdw/connection.c b/contrib/postgres_fdw/connection.c
index 304f3c20f83..53264ecbf93 100644
--- a/contrib/postgres_fdw/connection.c
+++ b/contrib/postgres_fdw/connection.c
@@ -472,6 +472,26 @@ pgfdw_security_check(const char **keywords, const char **values, UserMapping *us
errhint("Target server's authentication method must be changed or password_required=false set in the user mapping attributes.")));
}
+/*
+ * Custom notice processor for remote server connection.
+ */
+static void
+notice_processor(void *arg, const char *message)
+{
+ int len;
+
+ /*
+ * Trim the trailing newline from the message text passed to the notice
+ * processor, as it always includes one, to produce cleaner log output.
+ */
+ len = strlen(message);
+ if (len > 0 && message[len - 1] == '\n')
+ len--;
+
+ ereport(LOG,
+ errmsg("received message from remote server: %.*s", len, message));
+}
+
/*
* Connect to remote server using specified server and user mapping properties.
*/
@@ -625,6 +645,13 @@ connect_pg_server(ForeignServer *server, UserMapping *user)
server->servername),
errdetail_internal("%s", pchomp(PQerrorMessage(conn)))));
+ /*
+ * Set a custom notice processor so that NOTICEs, WARNINGs, and
+ * similar messages from the remote server connection are reported via
+ * ereport(), instead of being printed to stderr.
+ */
+ PQsetNoticeProcessor(conn, notice_processor, NULL);
+
/* Perform post-connection security checks. */
pgfdw_security_check(keywords, values, user, conn);
--
2.43.0
