From 8b5295fa533104f59348a6e9a5418804f27b82fe Mon Sep 17 00:00:00 2001
From: Kienan Stewart <kstewart@efficios.com>
Date: Fri, 15 Nov 2024 10:55:39 -0500
Subject: [PATCH] lttng-relayd: Add `--sig-parent` parameter
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Change-Id: I3a456f43de7ba2e557c1ca1c98466421e78e2f2e
Signed-off-by: Kienan Stewart <kstewart@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---
 doc/man/lttng-relayd.8.txt    |  9 ++++++++-
 src/bin/lttng-relayd/main.cpp | 16 +++++++++++++++-
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/doc/man/lttng-relayd.8.txt b/doc/man/lttng-relayd.8.txt
index 3f38b2fe0..f55149732 100644
--- a/doc/man/lttng-relayd.8.txt
+++ b/doc/man/lttng-relayd.8.txt
@@ -18,7 +18,7 @@ SYNOPSIS
              [option:--live-port='URL'] [option:--output='DIR'] [option:--group='GROUP']
              [option:--verbose]... [option:--working-directory='DIR']
              [option:--group-output-by-host | option:--group-output-by-session] [option:--disallow-clear]
-	     [option:--dynamic-port-allocation] [option:--pid-file='FILE']
+	     [option:--dynamic-port-allocation] [option:--pid-file='FILE'] [option:--sig-parent]
 
 
 DESCRIPTION
@@ -241,6 +241,13 @@ option:-P, option:--pid-file::
 +
 This file is not otherwise used by lttng-relayd and is removed at shutdown.
 
+option:-S, option:--sig-parent::
+    Send the `USR1` signal to the parent process to notify readiness.
++
+You can also use the option:--daemonize or option:--background option,
+in which case `lttng-relayd` ensures the daemon is ready to receive
+client commands before it exits.
+
 Output
 ~~~~~~
 See the ``<<output-directory,Output directory>>'' section above to learn
diff --git a/src/bin/lttng-relayd/main.cpp b/src/bin/lttng-relayd/main.cpp
index c5485dfa1..e4c121538 100644
--- a/src/bin/lttng-relayd/main.cpp
+++ b/src/bin/lttng-relayd/main.cpp
@@ -99,7 +99,7 @@ enum relay_connection_status {
 /* command line options */
 char *opt_output_path, *opt_working_directory, *opt_pid_file = nullptr;
 static int opt_daemon, opt_background, opt_print_version,
-	opt_allow_clear = 1, opt_dynamic_port_allocation = 0;
+	opt_allow_clear = 1, opt_dynamic_port_allocation = 0, opt_sig_parent = 0;
 enum relay_group_output_by opt_group_output_by = RELAYD_GROUP_OUTPUT_BY_UNKNOWN;
 
 /* Argument variables */
@@ -272,6 +272,12 @@ static struct option long_options[] = {
 	},
 	{ "disallow-clear", 0, nullptr, 'x' },
 	{ "dynamic-port-allocation", 0, nullptr, '\0' },
+	{
+		"sig-parent",
+		0,
+		nullptr,
+		'S'
+	},
 	{
 		nullptr,
 		0,
@@ -478,6 +484,9 @@ static int set_option(int opt, const char *arg, const char *optname)
 		/* Disallow clear */
 		opt_allow_clear = 0;
 		break;
+	case 'S':
+		opt_sig_parent = getppid();
+		break;
 	default:
 		/* Unknown option or other error.
 		 * Error is printed by getopt, just return */
@@ -4620,6 +4629,11 @@ int main(int argc, char **argv)
 	 * signal that asks threads to teardown).
 	 */
 
+	/* Initialization complete, signal parent PID if necessary. */
+	if (opt_sig_parent != 0) {
+		kill(opt_sig_parent, SIGUSR1);
+	}
+
 	ret = relayd_live_join();
 	if (ret) {
 		retval = -1;
-- 
2.39.5