[Fastboot] Delay LLDP service for better fastboot performance (#10568)

- Why I did it
Profiling the system state on init after fast-reboot during create_switch function execution, it is possible to see few python scripts running at the same time.
This parallel execution consume CPU time and the duration of create_switch is longer than it should be.
Following this finding, and the motivation to ensure these services will not interfere in the future, LLDP is delayed in 90 seconds until the system finish the init flow after fastboot.

- How I did it
Add a timer for LLDP service.
Copy the timer file to the host bin image.

- How to verify it
Run fast-reboot on MLNX platform and observe faster create_switch execution time.
This PR is dependent on PR: #10567

files/build_templates/init_cfg.json.j2

@@ -29,7 +29,7 @@
     },
 {%- set features = [("bgp", "enabled", false, "enabled"),
                    ("database", "always_enabled", false, "always_enabled"),
-                   ("lldp", "enabled", false, "enabled"),
+                   ("lldp", "enabled", true, "enabled"),
                    ("pmon", "enabled", false, "enabled"),
                    ("radv", "enabled", false, "enabled"),
                    ("snmp", "enabled", true, "enabled"),

files/build_templates/lldp.timer.j2

@@ -0,0 +1 @@
+per_namespace/lldp.timer.j2

files/build_templates/per_namespace/lldp.service.j2

@@ -20,6 +20,3 @@ ExecStartPre=/usr/local/bin/{{docker_container_name}}.sh start{% if multi_instan
 ExecStart=/usr/local/bin/{{docker_container_name}}.sh wait{% if multi_instance == 'true' %} %i{% endif %}
 ExecStop=/usr/local/bin/{{docker_container_name}}.sh stop{% if multi_instance == 'true' %} %i{% endif %}
 RestartSec=30
-
-[Install]
-WantedBy=sonic.target

files/build_templates/per_namespace/lldp.timer.j2

@@ -0,0 +1,12 @@
+[Unit]
+# This delay is for fast/warm reboot performance
+Description=Delays LLDP docker until SONiC has started
+PartOf=lldp{% if multi_instance == 'true' %}@%i{% endif %}.service
+
+[Timer]
+OnUnitActiveSec=0 sec
+OnBootSec=1min 30 sec
+Unit=lldp{% if multi_instance == 'true' %}@%i{% endif %}.service
+
+[Install]
+WantedBy=timers.target sonic.target sonic-delayed.target

files/build_templates/sonic_debian_extension.j2

@@ -774,6 +774,19 @@ if [ -f {{service}} ]; then
     echo "{{service}}" | sudo tee -a $GENERATED_SERVICE_FILE
 fi
 {% endfor %}
+{% for timer in installer_timers.split(' ') -%}
+if [ -f {{timer}} ]; then
+    sudo cp {{timer}} $FILESYSTEM_ROOT_USR_LIB_SYSTEMD_SYSTEM
+
+    {% if "@" in timer %}
+    MULTI_INSTANCE="{{timer}}"
+    SINGLE_INSTANCE=${MULTI_INSTANCE/"@"}
+    sudo cp $SINGLE_INSTANCE $FILESYSTEM_ROOT_USR_LIB_SYSTEMD_SYSTEM
+    {% endif %}
+
+    echo "{{timer}}" | sudo tee -a $GENERATED_SERVICE_FILE
+fi
+{% endfor %}
 if [ -f iccpd.service ]; then
     sudo LANG=C chroot $FILESYSTEM_ROOT systemctl disable iccpd.service
 fi

files/scripts/syncd.sh

@@ -50,6 +50,13 @@ function waitplatform() {
         /bin/systemctl start pmon
         debug "Started pmon service"
     fi
+    if [[ x"$BOOT_TYPE" = @(x"fast"|x"warm"|x"fastfast") ]]; then
+        debug "LLDP service is delayed by a timer for better fast/warm boot performance"
+    else
+        debug "Starting lldp service..."
+        /bin/systemctl start lldp
+        debug "Started lldp service"
+    fi
 }
 
 function stopplatform1() {

slave.mk

@@ -1162,6 +1162,14 @@ $(addprefix $(TARGET_PATH)/, $(SONIC_INSTALLERS)) : $(TARGET_PATH)/% : \
 				$(eval $(docker:-dbg.gz=.gz)_GLOBAL = yes)
 			)
 		fi
+		if [ -f files/build_templates/$($(docker:-dbg.gz=.gz)_CONTAINER_NAME).timer.j2 ]; then
+			j2 files/build_templates/$($(docker:-dbg.gz=.gz)_CONTAINER_NAME).timer.j2 > $($(docker:-dbg.gz=.gz)_CONTAINER_NAME).timer
+
+			# Set the flag GLOBAL_TIMER for all the global system-wide dockers timers.
+			$(if $(shell ls files/build_templates/$($(docker:-dbg.gz=.gz)_CONTAINER_NAME).timer.j2 2>/dev/null),\
+				$(eval $(docker:-dbg.gz=.gz)_GLOBAL_TIMER = yes)
+			)
+		fi
 		# Any service template, inside instance directory, will be used to generate .service and @.service file.
 		if [ -f files/build_templates/per_namespace/$($(docker:-dbg.gz=.gz)_CONTAINER_NAME).service.j2 ]; then
 			export multi_instance="true"
@@ -1172,6 +1180,16 @@ $(addprefix $(TARGET_PATH)/, $(SONIC_INSTALLERS)) : $(TARGET_PATH)/% : \
 			export multi_instance="false"
 			j2 files/build_templates/per_namespace/$($(docker:-dbg.gz=.gz)_CONTAINER_NAME).service.j2 > $($(docker:-dbg.gz=.gz)_CONTAINER_NAME).service
 		fi
+		# Any timer template, inside instance directory, will be used to generate .timer and @.timer file.
+		if [ -f files/build_templates/per_namespace/$($(docker:-dbg.gz=.gz)_CONTAINER_NAME).timer.j2 ]; then
+			export multi_instance="true"
+			j2 files/build_templates/per_namespace/$($(docker:-dbg.gz=.gz)_CONTAINER_NAME).timer.j2 > $($(docker:-dbg.gz=.gz)_CONTAINER_NAME)@.timer
+			$(if $(shell ls files/build_templates/per_namespace/$($(docker:-dbg.gz=.gz)_CONTAINER_NAME).timer.j2 2>/dev/null),\
+				$(eval $(docker:-dbg.gz=.gz)_TEMPLATE_TIMER = yes)
+			)
+			export multi_instance="false"
+			j2 files/build_templates/per_namespace/$($(docker:-dbg.gz=.gz)_CONTAINER_NAME).timer.j2 > $($(docker:-dbg.gz=.gz)_CONTAINER_NAME).timer
+		fi
 		# Any service template, inside share_image directory, will be used to generate -chassis.service file.
 		# TODO: need better way to name the image-shared service
 		if [ -f files/build_templates/share_image/$($(docker:-dbg.gz=.gz)_CONTAINER_NAME).service.j2 ]; then
@@ -1209,7 +1227,20 @@ $(addprefix $(TARGET_PATH)/, $(SONIC_INSTALLERS)) : $(TARGET_PATH)/% : \
 			$(eval SERVICES += "$(addsuffix -chassis.service, $($(docker:-dbg.gz=.gz)_CONTAINER_NAME))")
 		)
 	)
+	# Marks template timers with an "@" according to systemd convention
+	# If the $($docker)_TEMPLATE_TIMER) variable is set, the timer will be treated as a template
+	# If the $($docker)_GLOBAL_TIMER) and $($docker)_TEMPLATE_TIMER) variables are set the timer will be added both as a global and template timer.
+	$(foreach docker, $($*_DOCKERS),\
+		$(if $($(docker:-dbg.gz=.gz)_TEMPLATE_TIMER),\
+			$(if $($(docker:-dbg.gz=.gz)_GLOBAL_TIMER),\
+				$(eval TIMERS += "$(addsuffix .timer, $($(docker:-dbg.gz=.gz)_CONTAINER_NAME))")\
+			)\
+			$(eval TIMERS += "$(addsuffix @.timer, $($(docker:-dbg.gz=.gz)_CONTAINER_NAME))"),\
+			$(eval TIMERS += "$(addsuffix .timer, $($(docker:-dbg.gz=.gz)_CONTAINER_NAME))")
+		)
+	)
 	export installer_services="$(SERVICES)"
+	export installer_timers="$(TIMERS)"
 
 	export installer_extra_files="$(foreach docker, $($*_DOCKERS), $(foreach file, $($(docker:-dbg.gz=.gz)_BASE_IMAGE_FILES), $($(docker:-dbg.gz=.gz)_PATH)/base_image_files/$(file)))"