WEBVTT 00:00.350 --> 00:02.390 Along with the life cycle nodes. 00:02.420 --> 00:09.890 Roscoe also offers a command line interface to manage these type of nodes to view their state and to 00:09.890 --> 00:15.950 view their available transition while in the current state, and also to activate certain transitions 00:15.980 --> 00:18.650 that change the life cycle nodes state. 00:19.340 --> 00:22.980 To see how all of this works and how we can use this interface. 00:23.000 --> 00:26.810 Let's start the lifecycle nodes that we create in the previous lesson. 00:26.990 --> 00:28.850 So let's open a new terminal. 00:29.750 --> 00:33.470 Let's go to the workspace and let's source it. 00:35.030 --> 00:46.340 And now let's run like a normal node from the Arduino boot CP Examples package. 00:46.370 --> 00:47.950 The life cycle Node. 00:47.960 --> 00:54.560 So the one that we called Simple Life Cycle Node and let's press enter. 00:55.280 --> 00:56.180 At the startup. 00:56.180 --> 01:00.410 This node does nothing and just initialize the life cycle node. 01:00.560 --> 01:02.300 And so we can confirm this. 01:02.330 --> 01:09.140 If we open a new terminal and here we can start interacting with the command line of Ros to which the 01:09.140 --> 01:14.950 life cycle nodes with the command ros2 life cycle. 01:15.650 --> 01:21.770 And then let's use the nodes command to have a list of all the life cycle nodes that are currently available 01:21.770 --> 01:22.400 in Ros two. 01:22.490 --> 01:25.750 And we can see that among these there is only one node. 01:25.760 --> 01:30.470 And so this is the simple life cycle node that we have just created and started. 01:31.090 --> 01:37.440 Now, of course it will be in the Unconfigured state since we just started it and we can verify. 01:37.450 --> 01:47.920 So by using the command ros2 lifecycle, get followed by the name of the node, which is the simple 01:47.920 --> 01:49.070 lifecycle node. 01:49.090 --> 01:51.070 So let's press enter. 01:51.070 --> 01:54.910 And actually we can see that as we were expecting this node. 01:54.910 --> 01:58.780 So this lifecycle node is in the Unconfigured state. 01:58.900 --> 02:04.630 And furthermore, we also know that while the node is in this state, so in the Unconfigured state, 02:04.660 --> 02:08.140 the node has not yet subscribed to any topic. 02:08.230 --> 02:17.830 And indeed if we use the command Ros2 topic list, we can see that the topic chapter is not here in 02:17.830 --> 02:19.450 the Unconfigured state. 02:19.450 --> 02:25.330 So while the node is in this state, there are only two active transitions. 02:25.360 --> 02:31.940 The configure transition, which would bring the state machine to the inactive state and the shutdown 02:31.940 --> 02:36.710 transition, which instead would bring the state machine into the finalized state. 02:37.010 --> 02:42.980 We can confirm this, so we can confirm that the only two available transition are the configure and 02:42.980 --> 02:49.040 the shutdown by using the command ros2 lifecycle. 02:49.940 --> 02:50.570 List. 02:51.140 --> 02:56.660 And then we want the list of the transition active on the Simple Life Cycle node. 02:56.720 --> 02:58.460 So let's press enter. 02:58.610 --> 03:05.210 And indeed, we can confirm that in the current state there is available only the configured transition 03:05.210 --> 03:07.190 and the shutdown transition. 03:07.190 --> 03:09.140 So only these two transitions. 03:09.650 --> 03:12.890 Let's activate, for example, the configure transition. 03:12.890 --> 03:23.270 So the first one with the command Ros2 life cycle set, then the name of the node, which is the simple 03:23.270 --> 03:24.280 life cycle node. 03:24.290 --> 03:29.780 And then here let's activate the configure transition. 03:29.780 --> 03:31.670 So let's type, configure. 03:31.940 --> 03:33.530 So let's press enter. 03:33.560 --> 03:39.860 We also get the output of the terminal that says that the transition ended successfully. 03:39.980 --> 03:45.770 And also we can see that here in the terminal where we launched the Simple Life Cycle node, we get 03:45.770 --> 03:51.120 notified that the on configure function has been called has been executed. 03:51.210 --> 04:01.380 And also we can double check it by using again the command Ros2 life cycle get and let's get the status 04:01.380 --> 04:03.060 of the simple life cycle node. 04:03.540 --> 04:08.160 And now it is in the inactive state as we were expecting. 04:08.870 --> 04:09.710 In this state. 04:09.710 --> 04:13.640 The node has already created the subscription to the chatter topic. 04:13.820 --> 04:22.880 And so if we open a new terminal and we launch the Ros2 topic list command, now we can see that the 04:22.880 --> 04:24.320 chatter topic appears. 04:24.320 --> 04:32.180 So this one since the node is in the inactive state and in this state is where the subscriber is created. 04:32.600 --> 04:41.360 Anyway, if we try to publish a new message within this topic, so we trust to topic publish within 04:41.360 --> 04:42.440 the chatter topic. 04:42.440 --> 04:46.730 So here there are accepted messages of type string. 04:47.210 --> 04:55.100 Then let's use a double quote and then let's for example, print the message I So if we press enter 04:55.130 --> 05:02.450 now, basically this terminal is publishing repeatedly the message I and also if it is continuously 05:02.450 --> 05:08.060 publishing this message to the chatter topic, we see that nothing happens in this simple lifecycle 05:08.060 --> 05:08.610 node. 05:08.610 --> 05:13.080 So nothing happens because the simple lifecycle node is in the inactive state. 05:13.080 --> 05:19.920 And while in this state it is not receiving any message from the subscription, in order to do so, 05:19.920 --> 05:22.080 it must be in the active state. 05:22.530 --> 05:28.320 So to move this one to the active state, so the lifecycle node to the active state, we need to use 05:28.320 --> 05:33.450 the command Ros2 lifecycle list. 05:34.740 --> 05:36.510 And so the simple lifecycle node. 05:37.470 --> 05:43.680 Now we can see that while in the inactive state there are only three transitions available. 05:43.710 --> 05:48.190 The clean up, then the activate and then the shut down. 05:48.210 --> 05:50.400 Let's change the status of the node. 05:50.400 --> 05:57.090 So let's activate it with the command Ros2 life cycle set. 05:57.240 --> 06:00.060 And so let's set the status of the simple cycle node. 06:00.060 --> 06:01.020 So let's. 06:03.310 --> 06:06.730 Use the activate transition. 06:06.730 --> 06:08.320 So let's press enter. 06:09.710 --> 06:12.950 And then now we can see that two things start to happen. 06:12.980 --> 06:19.190 The first is that the on activate function is being called, and the second is that we are starting 06:19.190 --> 06:25.730 receiving the messages that here in this terminal we are still publishing within the chatter topic. 06:25.850 --> 06:30.920 And so finally it is in the active state and starts receiving the messages. 06:31.950 --> 06:33.740 Again while in this state. 06:33.750 --> 06:39.990 So while in the active state, let's see which are the transition that are available for our state machine 06:39.990 --> 06:44.370 with the Ros life cycle. 06:45.920 --> 06:48.920 List and then the name of the node. 06:49.310 --> 06:56.060 And now we can see that while in the active state, there are only two transitions the deactivate and 06:56.060 --> 06:57.230 the shut down. 06:57.740 --> 07:00.380 For example, let's trigger the first one. 07:00.380 --> 07:08.120 So the deactivate transaction with the Ros two lifecycle set. 07:08.990 --> 07:15.090 And on the simple lifecycle node, let's set the transition, the activate. 07:15.110 --> 07:16.880 So let's press enter. 07:17.000 --> 07:18.440 And we can see that here. 07:18.440 --> 07:21.950 We get notified that the on deactivate function has been called. 07:21.950 --> 07:26.240 And also we can see that no more messages are printed in the terminal. 07:26.240 --> 07:30.560 So we are not receiving any more messages from the chatter topic. 07:30.560 --> 07:33.640 And as soon as we start it again. 07:33.650 --> 07:41.120 So if we again move the state machine to the state active with the Activate transaction. 07:42.490 --> 07:44.530 The flow of messages starts again. 07:44.530 --> 07:49.600 And so the subscriber starts again to listen and to print messages in the terminal.