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

1 files changed, 31 insertions, 0 deletions

diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 47375e5bfaa..ecd04655c2a 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 (IsExternalConnectionBackend(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 (IsExternalConnectionBackend(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 (IsExternalConnectionBackend(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