v14-0002-Add-connection-establishment-duration-logging.patch

From f307fb571230e8aa452a19d68a25933f500df4f4 Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplageman@gmail.com>
Date: Wed, 5 Mar 2025 18:05:19 -0500
Subject: [PATCH v14 2/2] Add connection establishment duration logging

Add log_connections option 'setup_durations' which logs durations of
several key parts of connection establishment and backend setup.

For an incoming connection, starting from when the postmaster gets a
socket from accept() and ending when the forked child backend is first
ready for query, there are multiple steps that could each take longer
than expected due to external factors. This logging provides visibility
into authentication and fork duration as well as the end-to-end
connection establishment and backend initialization time.

To make this portable, the timings captured in the postmaster (socket
creation time, fork initiation time) are passed through the
BackendStartupData.

Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Reviewed-by: Fujii Masao <masao.fujii@oss.nttdata.com>
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Jacob Champion <jacob.champion@enterprisedb.com>
Reviewed-by: Jelte Fennema-Nio <postgres@jeltef.nl>
Reviewed-by: Guillaume Lelarge <guillaume.lelarge@dalibo.com>
Discussion: https://postgr.es/m/flat/CAAKRu_b_smAHK0ZjrnL5GRxnAVWujEXQWpLXYzGbmpcZd3nLYw%40mail.gmail.com
---
 doc/src/sgml/config.sgml                      | 13 +++++
 src/backend/postmaster/launch_backend.c       | 31 ++++++++++
 src/backend/postmaster/postmaster.c           |  6 ++
 src/backend/tcop/backend_startup.c            | 11 ++++
 src/backend/tcop/postgres.c                   | 33 +++++++++++
 src/backend/utils/init/postinit.c             |  6 ++
 src/backend/utils/misc/postgresql.conf.sample |  2 +-
 src/include/miscadmin.h                       |  7 +++
 src/include/tcop/backend_startup.h            | 57 +++++++++++++++++--
 src/include/utils/timestamp.h                 |  9 +++
 src/test/authentication/t/001_password.pl     | 18 +++++-
 src/tools/pgindent/typedefs.list              |  1 +
 12 files changed, 188 insertions(+), 6 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index d939d99d6e8..403d959ab30 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -7369,6 +7369,19 @@ local0.*    /var/log/postgresql
            </entry>
           </row>
 
+          <row>
+           <entry><literal>setup_durations</literal></entry>
+           <entry>
+            Logs the time spent establishing the connection and setting up the
+            backend at the time the connection is ready to execute its first
+            query. The log message includes the total setup duration, starting
+            from the postmaster accepting the incoming connection and ending
+            when the connection is ready for query. It also includes the time
+            it took to fork the new backend and the time it took to
+            authenticate the user.
+           </entry>
+          </row>
+
           <row>
            <entry><literal>all</literal></entry>
            <entry>
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 47375e5bfaa..74b0c33adaa 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -232,6 +232,10 @@ postmaster_child_launch(BackendType child_type, int child_slot,
 
 	Assert(IsPostmasterEnvironment && !IsUnderPostmaster);
 
+	/* Capture time Postmaster initiates process creation for logging */
+	if (IsConnectionBackend(child_type))
+		((BackendStartupData *) startup_data)->fork_started = GetCurrentTimestamp();
+
 #ifdef EXEC_BACKEND
 	pid = internal_forkexec(child_process_kinds[child_type].name, child_slot,
 							startup_data, startup_data_len, client_sock);
@@ -240,6 +244,16 @@ postmaster_child_launch(BackendType child_type, int child_slot,
 	pid = fork_process();
 	if (pid == 0)				/* child */
 	{
+		/* Capture and transfer timings that may be needed for logging */
+		if (IsConnectionBackend(child_type))
+		{
+			conn_timing.socket_create =
+				((BackendStartupData *) startup_data)->socket_created;
+			conn_timing.fork_start =
+				((BackendStartupData *) startup_data)->fork_started;
+			conn_timing.fork_end = GetCurrentTimestamp();
+		}
+
 		/* Close the postmaster's sockets */
 		ClosePostmasterPorts(child_type == B_LOGGER);
 
@@ -586,11 +600,18 @@ SubPostmasterMain(int argc, char *argv[])
 	char	   *child_kind;
 	BackendType child_type;
 	bool		found = false;
+	TimestampTz fork_end;
 
 	/* In EXEC_BACKEND case we will not have inherited these settings */
 	IsPostmasterEnvironment = true;
 	whereToSendOutput = DestNone;
 
+	/*
+	 * Capture the end of process creation for logging. We don't include the
+	 * time spent copying data from shared memory and setting up the backend.
+	 */
+	fork_end = GetCurrentTimestamp();
+
 	/* Setup essential subsystems (to ensure elog() behaves sanely) */
 	InitializeGUCOptions();
 
@@ -648,6 +669,16 @@ SubPostmasterMain(int argc, char *argv[])
 	/* Read in remaining GUC variables */
 	read_nondefault_variables();
 
+	/* Capture and transfer timings that may be needed for log_connections */
+	if (IsConnectionBackend(child_type))
+	{
+		conn_timing.socket_create =
+			((BackendStartupData *) startup_data)->socket_created;
+		conn_timing.fork_start =
+			((BackendStartupData *) startup_data)->fork_started;
+		conn_timing.fork_end = fork_end;
+	}
+
 	/*
 	 * Check that the data directory looks valid, which will also check the
 	 * privileges on the data directory and update our umask and file/group
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index b4f34c57a1b..57155c00e01 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -3477,6 +3477,12 @@ BackendStartup(ClientSocket *client_sock)
 	BackendStartupData startup_data;
 	CAC_state	cac;
 
+	/*
+	 * Capture time that Postmaster got a socket from accept (for logging
+	 * connection establishment and setup total duration).
+	 */
+	startup_data.socket_created = GetCurrentTimestamp();
+
 	/*
 	 * Allocate and assign the child slot.  Note we must do this before
 	 * forking, so that we can handle failures (out of memory or child-process
diff --git a/src/backend/tcop/backend_startup.c b/src/backend/tcop/backend_startup.c
index 962b6e60002..27c0b3c2b04 100644
--- a/src/backend/tcop/backend_startup.c
+++ b/src/backend/tcop/backend_startup.c
@@ -46,6 +46,16 @@ bool		Trace_connection_negotiation = false;
 uint32		log_connections = 0;
 char	   *log_connections_string = NULL;
 
+/* Other globals */
+
+/*
+ * ConnectionTiming stores timestamps of various points in connection
+ * establishment and setup.
+ * ready_for_use is initialized to a special value here so we can check if
+ * we've already set it before doing so in PostgresMain().
+ */
+ConnectionTiming conn_timing = {.ready_for_use = TIMESTAMP_MINUS_INFINITY};
+
 static void BackendInitialize(ClientSocket *client_sock, CAC_state cac);
 static int	ProcessSSLStartup(Port *port);
 static int	ProcessStartupPacket(Port *port, bool ssl_done, bool gss_done);
@@ -1006,6 +1016,7 @@ validate_log_connections_options(List *elemlist, uint32 *flags)
 			{"receipt", LOG_CONNECTION_RECEIPT},
 			{"authentication", LOG_CONNECTION_AUTHENTICATION},
 			{"authorization", LOG_CONNECTION_AUTHORIZATION},
+			{"setup_durations", LOG_CONNECTION_SETUP_DURATIONS},
 			{"all", LOG_CONNECTION_ALL},
 		};
 
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 947ffb40421..f2cae40b53d 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -66,6 +66,7 @@
 #include "storage/proc.h"
 #include "storage/procsignal.h"
 #include "storage/sinval.h"
+#include "tcop/backend_startup.h"
 #include "tcop/fastpath.h"
 #include "tcop/pquery.h"
 #include "tcop/tcopprot.h"
@@ -4607,6 +4608,38 @@ PostgresMain(const char *dbname, const char *username)
 			/* Report any recently-changed GUC options */
 			ReportChangedGUCOptions();
 
+			/*
+			 * The first time this backend is ready for query, log the
+			 * durations of the different components of connection
+			 * establishment and setup.
+			 */
+			if (conn_timing.ready_for_use == TIMESTAMP_MINUS_INFINITY &&
+				(log_connections & LOG_CONNECTION_SETUP_DURATIONS) &&
+				IsConnectionBackend(MyBackendType))
+			{
+				uint64		total_duration,
+							fork_duration,
+							auth_duration;
+
+				conn_timing.ready_for_use = GetCurrentTimestamp();
+
+				total_duration =
+					TimestampDifferenceMicroseconds(conn_timing.socket_create,
+													conn_timing.ready_for_use);
+				fork_duration =
+					TimestampDifferenceMicroseconds(conn_timing.fork_start,
+													conn_timing.fork_end);
+				auth_duration =
+					TimestampDifferenceMicroseconds(conn_timing.auth_start,
+													conn_timing.auth_end);
+
+				ereport(LOG,
+						errmsg("connection ready: setup total=%.3f ms, fork=%.3f ms, authentication=%.3f ms",
+							   (double) total_duration / NS_PER_US,
+							   (double) fork_duration / NS_PER_US,
+							   (double) auth_duration / NS_PER_US));
+			}
+
 			ReadyForQuery(whereToSendOutput);
 			send_ready_for_query = false;
 		}
diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c
index 6c207e17768..4b2faf1ba9d 100644
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -235,6 +235,9 @@ PerformAuthentication(Port *port)
 	}
 #endif
 
+	/* Capture authentication start time for logging */
+	conn_timing.auth_start = GetCurrentTimestamp();
+
 	/*
 	 * Set up a timeout in case a buggy or malicious client fails to respond
 	 * during authentication.  Since we're inside a transaction and might do
@@ -253,6 +256,9 @@ PerformAuthentication(Port *port)
 	 */
 	disable_timeout(STATEMENT_TIMEOUT, false);
 
+	/* Capture authentication end time for logging */
+	conn_timing.auth_end = GetCurrentTimestamp();
+
 	if (log_connections & LOG_CONNECTION_AUTHORIZATION)
 	{
 		StringInfoData logmsg;
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index c291c05d181..d2bd329a587 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -580,7 +580,7 @@
 #log_checkpoints = on
 #log_connections = '' # log aspects of connection setup
           # options include receipt, authentication, authorization,
-          # and all to log all of these aspects
+          # setup_durations, and all to log all of these aspects
 #log_disconnections = off
 #log_duration = off # log statement duration
 #log_error_verbosity = default		# terse, default, or verbose messages
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index a2b63495eec..312eb3f9529 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -394,6 +394,13 @@ extern PGDLLIMPORT BackendType MyBackendType;
 	(AmAutoVacuumLauncherProcess() || \
 	 AmLogicalSlotSyncWorkerProcess())
 
+/*
+ * Backend types that are spawned by the postmaster to serve a client
+ * or replication connection.
+ */
+#define IsConnectionBackend(backend_type) \
+	(backend_type == B_BACKEND || backend_type == B_WAL_SENDER)
+
 extern const char *GetBackendTypeDesc(BackendType backendType);
 
 extern void SetDatabasePath(const char *path);
diff --git a/src/include/tcop/backend_startup.h b/src/include/tcop/backend_startup.h
index e00851a004e..2912ef80288 100644
--- a/src/include/tcop/backend_startup.h
+++ b/src/include/tcop/backend_startup.h
@@ -14,11 +14,16 @@
 #ifndef BACKEND_STARTUP_H
 #define BACKEND_STARTUP_H
 
+#include "utils/timestamp.h"
+
 /* GUCs */
 extern PGDLLIMPORT bool Trace_connection_negotiation;
 extern PGDLLIMPORT uint32 log_connections;
 extern PGDLLIMPORT char *log_connections_string;
 
+/* Other globals */
+extern PGDLLIMPORT struct ConnectionTiming conn_timing;
+
 /*
  * CAC_state is passed from postmaster to the backend process, to indicate
  * whether the connection should be accepted, or if the process should just
@@ -39,14 +44,27 @@ typedef enum CAC_state
 typedef struct BackendStartupData
 {
 	CAC_state	canAcceptConnections;
+
+	/*
+	 * Time at which the connection client socket is created. Only used for
+	 * client and wal sender connections.
+	 */
+	TimestampTz socket_created;
+
+	/*
+	 * Time at which the postmaster initiates process creation -- either
+	 * through fork or otherwise. Only used for client and wal sender
+	 * connections.
+	 */
+	TimestampTz fork_started;
 } BackendStartupData;
 
 /*
  * Granular control over which messages to log for the log_connections GUC.
  *
- * RECEIPT, AUTHENTICATION, and AUTHORIZATION are different aspects of
- * connection establishment and backend setup for which we may emit a log
- * message.
+ * RECEIPT, AUTHENTICATION, AUTHORIZATION, and SETUP_DURATIONS are different
+ * aspects of connection establishment and backend setup for which we may emit
+ * a log message.
  *
  * ALL is a convenience alias equivalent to all of the above aspects.
  *
@@ -58,6 +76,7 @@ typedef enum LogConnectionOption
 	LOG_CONNECTION_RECEIPT = (1 << 0),
 	LOG_CONNECTION_AUTHENTICATION = (1 << 1),
 	LOG_CONNECTION_AUTHORIZATION = (1 << 2),
+	LOG_CONNECTION_SETUP_DURATIONS = (1 << 3),
 	LOG_CONNECTION_ON =
 		LOG_CONNECTION_RECEIPT |
 		LOG_CONNECTION_AUTHENTICATION |
@@ -65,9 +84,39 @@ typedef enum LogConnectionOption
 	LOG_CONNECTION_ALL =
 		LOG_CONNECTION_RECEIPT |
 		LOG_CONNECTION_AUTHENTICATION |
-		LOG_CONNECTION_AUTHORIZATION,
+		LOG_CONNECTION_AUTHORIZATION |
+		LOG_CONNECTION_SETUP_DURATIONS,
 } LogConnectionOption;
 
+/*
+ * A collection of timings of various stages of connection establishment and
+ * setup for client backends and WAL senders.
+ *
+ * Used to emit the setup_durations log message for the log_connections GUC.
+ */
+typedef struct ConnectionTiming
+{
+	/*
+	 * The time at which the client socket is created and the time at which
+	 * the connection is fully set up and first ready for query. Together
+	 * these represent the total connection establishment and setup time.
+	 */
+	TimestampTz socket_create;
+	TimestampTz ready_for_use;
+
+	/* Time at which process creation was initiated */
+	TimestampTz fork_start;
+
+	/* Time at which process creation was completed */
+	TimestampTz fork_end;
+
+	/* Time at which authentication started */
+	TimestampTz auth_start;
+
+	/* Time at which authentication was finished */
+	TimestampTz auth_end;
+} ConnectionTiming;
+
 extern void BackendMain(const void *startup_data, size_t startup_data_len) pg_attribute_noreturn();
 
 #endif							/* BACKEND_STARTUP_H */
diff --git a/src/include/utils/timestamp.h b/src/include/utils/timestamp.h
index 9963bddc0ec..8c205859c3b 100644
--- a/src/include/utils/timestamp.h
+++ b/src/include/utils/timestamp.h
@@ -85,6 +85,15 @@ IntervalPGetDatum(const Interval *X)
 #define TimestampTzPlusMilliseconds(tz,ms) ((tz) + ((ms) * (int64) 1000))
 #define TimestampTzPlusSeconds(tz,s) ((tz) + ((s) * (int64) 1000000))
 
+/* Helper for simple subtraction between two timestamps */
+static inline uint64
+TimestampDifferenceMicroseconds(TimestampTz start_time,
+								TimestampTz stop_time)
+{
+	if (start_time >= stop_time)
+		return 0;
+	return (uint64) stop_time - start_time;
+}
 
 /* Set at postmaster start */
 extern PGDLLIMPORT TimestampTz PgStartTime;
diff --git a/src/test/authentication/t/001_password.pl b/src/test/authentication/t/001_password.pl
index e307dee5c48..8269c470b59 100644
--- a/src/test/authentication/t/001_password.pl
+++ b/src/test/authentication/t/001_password.pl
@@ -77,8 +77,22 @@ $node->start;
 # other tests are added to this file in the future
 $node->safe_psql('postgres', "CREATE DATABASE test_log_connections");
 
+my $log_connections = $node->safe_psql('test_log_connections', q(SHOW log_connections;));
+is($log_connections, 'on', qq(check log connections has expected value 'on'));
+
+$node->connect_ok('test_log_connections',
+	qq(log_connections 'on' works as expected for backwards compatibility),
+	log_like => [
+		qr/connection received/,
+		qr/connection authenticated/,
+		qr/connection authorized: user=\S+ database=test_log_connections/,
+	],
+	log_unlike => [
+		qr/connection ready/,
+	],);
+
 $node->safe_psql('test_log_connections',
-	q[ALTER SYSTEM SET log_connections = receipt,authorization;
+	q[ALTER SYSTEM SET log_connections = receipt,authorization,setup_durations;
 				   SELECT pg_reload_conf();]);
 
 $node->connect_ok('test_log_connections',
@@ -86,6 +100,7 @@ $node->connect_ok('test_log_connections',
 	log_like => [
 		qr/connection received/,
 		qr/connection authorized: user=\S+ database=test_log_connections/,
+		qr/connection ready/,
 	],
 	log_unlike => [
 		qr/connection authenticated/,
@@ -100,6 +115,7 @@ $node->connect_ok('test_log_connections',
 		qr/connection received/,
 		qr/connection authenticated/,
 		qr/connection authorized: user=\S+ database=test_log_connections/,
+		qr/connection ready/,
 	],);
 
 # Authentication tests
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 9e7f58adb18..a2e592dbbbb 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -484,6 +484,7 @@ ConnParams
 ConnStatusType
 ConnType
 ConnectionStateEnum
+ConnectionTiming
 ConsiderSplitContext
 Const
 ConstrCheck
-- 
2.34.1