On Thu, Mar 24, 2022 at 01:31:08PM -0700, Nathan Bossart wrote:
> A couple of other options to consider:
>
> 1) Always set log_min_messages to WARNING/ERROR/FATAL for 'postgres -C'.
> We might need some special logic for handling the case where the user is
> inspecting the log_min_messages parameter. With this approach, you'd
> probably never get extra output unless something was wrong (e.g., database
> already running when inspecting a runtime-computed GUC). Also, this would
> silence any extra output that you might see today with non-runtime-computed
> GUCs.
>
> 2) Add some way to skip just the shutdown message (e.g., a variable set
> when output_config_variable is true). With this approach, you wouldn't get
> extra output by default, but you still might if log_min_messages is set to
> something like DEBUG3. This wouldn't impact any extra output that you see
> today with non-runtime-computed GUCs.
I've attached a first attempt at option 1.
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
>From f36d04f5d19c673a7be788d6d4955b148f580095 Mon Sep 17 00:00:00 2001
From: Nathan Bossart <nathandboss...@gmail.com>
Date: Mon, 28 Mar 2022 10:12:23 -0700
Subject: [PATCH v3 1/1] Silence extra logging with 'postgres -C'.
Presently, the server may emit a variety of extra log messages when inspecting
GUC values. For example, when inspecting a runtime-computed GUC, the server
will always emit a "database system is shut down" LOG (unless the user has set
log_min_messages higher than LOG). To avoid these extra log messages, this
change sets log_min_messages to FATAL when -C is used (unless the user has set
it to PANIC). At FATAL, the user will still receive messages explaining why a
GUC's value cannot be inspected.
---
src/backend/postmaster/postmaster.c | 34 +++++++++++++++++++++++++----
1 file changed, 30 insertions(+), 4 deletions(-)
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 80bb269599..7ee20d7c69 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -897,6 +897,26 @@ PostmasterMain(int argc, char *argv[])
if (output_config_variable != NULL)
{
+ const char *logging_setting;
+ int flags;
+
+ /*
+ * Silence any extra log messages when -C is used. Before adjusting
+ * log_min_messages, we save its value in case the user is inspecting
+ * it. If we are inspecting a runtime-computed GUC, it is possible that
+ * a preloaded library's _PG_init() will override our custom setting for
+ * log_min_messages, but trying to deal with that is probably more
+ * trouble than it's worth.
+ *
+ * If the user has set log_min_messages to PANIC, we leave it at PANIC.
+ * This has the side effect of silencing helpful FATAL messages (e.g.,
+ * when trying to inspect a runtime-computed GUC on a running server),
+ * but presumably the user has set it there for good reason.
+ */
+ logging_setting = GetConfigOption("log_min_messages", false, false);
+ if (log_min_messages < FATAL)
+ SetConfigOption("log_min_messages", "FATAL", PGC_INTERNAL, PGC_S_OVERRIDE);
+
/*
* If this is a runtime-computed GUC, it hasn't yet been initialized,
* and the present value is not useful. However, this is a convenient
@@ -908,17 +928,23 @@ PostmasterMain(int argc, char *argv[])
* on running servers for those GUCs, but using this option now would
* lead to incorrect results for them.
*/
- int flags = GetConfigOptionFlags(output_config_variable, true);
+ flags = GetConfigOptionFlags(output_config_variable, true);
if ((flags & GUC_RUNTIME_COMPUTED) == 0)
{
+ const char *config_val;
+
/*
* "-C guc" was specified, so print GUC's value and exit. No
* extra permission check is needed because the user is reading
- * inside the data dir.
+ * inside the data dir. If we are inspecting log_min_messages,
+ * print the saved value.
*/
- const char *config_val = GetConfigOption(output_config_variable,
- false, false);
+ if (pg_strcasecmp(output_config_variable, "log_min_messages") == 0)
+ config_val = logging_setting;
+ else
+ config_val = GetConfigOption(output_config_variable,
+ false, false);
puts(config_val ? config_val : "");
ExitPostmaster(0);
--
2.25.1
