cancelGoalsBefore

Cancel goals sent by ROS 2 action client before timestamp

Since R2023a

Syntax

cancelGoalsBefore(client,timestamp)

cancelGoalsBefore(client,timestamp,CancelFcn=@cancelCallback)

Description

cancelGoalsBefore(client,timestamp) sends a cancel request for all the active goals sent by the ROS 2 action client client at or before the specified timestamp, timestamp. The function does not wait for the goals to be cancelled and returns immediately.

cancelGoalsBefore(client,timestamp,CancelFcn=@cancelCallback) specifies a callback function to execute when the cancel response reaches the ROS 2 action client using the name-value argument CancelFcn=@cancelCallback. The callback function must have the received cancel response message as the first input argument. You can provide additional data to the callback using multiple subsequent input arguments. This is indicated by the varargin variable. This is an example function header signature:

function cancelCallback(cancelMsg,varargin)

Note

To supply additional data to the callback function, you can specify one additional input argument. You must include both the callback function and the additional input argument as elements of a cell array while defining the CancelFcn name-value argument. For example:

cancelgoalsBefore(client,goalHandle,CancelFcn={@cancelCallback,4.5})

Examples

Send and Cancel ROS 2 Action Goals

This example shows how to send and cancel ROS 2 action goals. Action types must be set up beforehand with an action server running. This example uses the /fibonacci action. Follow these steps to set up the action server:

1. Create a ROS 2 package with the action definition. For instructions on setting up a /fibonacci action, see Creating an Action.

2. Create a ROS 2 package with the action server implementation. For more information on setting up the /fibonacci action server, see Writing an Action Server.

3. Use the ros2genmsg function for the ROS 2 package with action definition from Step 1, and generate action messages in MATLAB®.

To run the /fibonacci action server, use this command on the ROS 2 system:

ros2 run action_tutorials_cpp fibonacci_action_server

Set Up ROS 2 Action Client

Create a ROS 2 node.

node = ros2node("/node_1");

Create an action client for /fibonacci action by specifying the node, action name, and action type. Set the quality of service (QoS) parameters.Wait for the action client to connect to the server.

[client,goalMsg] = ros2actionclient(node,"fibonacci",...
"action_tutorials_interfaces/Fibonacci", ...
CancelServiceQoS=struct(Depth=200,History="keeplast"), ...
FeedbackTopicQoS=struct(Depth=200,History="keepall"));
status = waitForServer(client)

status = logical
   1

Before sending the goal, define the callback options framework for the goal execution process. In this example, you specify a callback function to execute when the server returns a feedback response.

callbackOpts = ros2ActionSendGoalOptions(FeedbackFcn=@helperFeedbackCallback);

Send and Cancel Goals

The /fibonacci action will calculate the /fibonacci sequence for a given order specified in the goal message. The goal message was returned when creating the action client and can be modified to send goals to the ROS action server. Set the order to an int32 value of 8.

goalMsg.order = int32(8);

Create a new goal message and set the order to an int32 value of 10.

goalMsg2 = ros2message(client);
goalMsg2.order = int32(10);

Send both the goals to the action server using the sendGoal function. Specify the same callback options for both goals.

goalHandle = sendGoal(client,goalMsg,callbackOpts);
goalHandle2 = sendGoal(client,goalMsg2,callbackOpts);

Goal with GoalUUID ca8dbca2b8608a6f2add01b298f6930 accepted by server, waiting for result!
Partial sequence feedback for goal ca8dbca2b8608a6f2add01b298f6930 is 0  1  1
Goal with GoalUUID f493913f4acd2224f31145ae74bbc35 accepted by server, waiting for result!
Partial sequence feedback for goal f493913f4acd2224f31145ae74bbc35 is 0  1  1

Cancel the specific goal associated with the sequence order 8. Use the goal handle object associated with that goal as input to the cancelGoal function, and specify the cancel callback to execute once the client receives the cancel response. This function returns immediately without waiting for the cancel response to arrive.

cancelGoal(client,goalHandle,CancelFcn=@helperCancelGoalCallback)

Goal ca8dbca2b8608a6f2add01b298f6930 is cancelled with return code 0

You can wait until the cancel response arrives from the server by using the cancelGoalAndWait function. Cancel the goal associated with the sequence order of 10 and wait until the client receives the cancel response.

cancelResponse = cancelGoalAndWait(client,goalHandle2)

cancelResponse = struct with fields:
              MessageType: 'action_msgs/CancelGoalResponse'
               ERROR_NONE: 0
           ERROR_REJECTED: 1
    ERROR_UNKNOWN_GOAL_ID: 2
    ERROR_GOAL_TERMINATED: 3
              return_code: 0
          goals_canceling: [1×1 struct]

Cancel Goals Before Timestamp

Send the goal message with sequence order 10. Note the timestamp in a ROS 2 message by using the ros2time function.

goalHandle = sendGoal(client,goalMsg2,callbackOpts);
timeStampMsg = ros2time(node,"now");

Goal with GoalUUID d8268c566b234e8784f0f1a8ec12b2 accepted by server, waiting for result!
Partial sequence feedback for goal d8268c566b234e8784f0f1a8ec12b2 is 0  1  1

Then, send a second goal message with sequence order 8. Note the timestamp.

goalHandle2 = sendGoal(client,goalMsg,callbackOpts);
timeStampMsg2 = ros2time(node,"now");

Goal with GoalUUID 9585bff2ba44bf60daa630a952b458be accepted by server, waiting for result!
Partial sequence feedback for goal 9585bff2ba44bf60daa630a952b458be is 0  1  1

Cancel the goal sent before the first time stamp using cancelGoalsBefore function.

cancelGoalsBefore(client,timeStampMsg,CancelFcn=@helperCancelGoalsCallback)

Goals cancelled with return code 0

Use the cancelGoalsBeforeAndWait function to cancel the goal sent before second time stamp and wait for the cancel response.

cancelResponse = cancelGoalsBeforeAndWait(client,timeStampMsg2)

cancelResponse = struct with fields:
              MessageType: 'action_msgs/CancelGoalResponse'
               ERROR_NONE: 0
           ERROR_REJECTED: 1
    ERROR_UNKNOWN_GOAL_ID: 2
    ERROR_GOAL_TERMINATED: 3
              return_code: 0
          goals_canceling: [1×1 struct]

Cancel All Goals

Cancel all the active goals that the client sent.

goalHandle = sendGoal(client,goalMsg,callbackOpts);
cancelAllGoals(client,CancelFcn=@helperCancelGoalsCallback);

Goals cancelled with return code 0

Cancel all the active goals that the client sent and wait for cancel response.

goalHandle2 = sendGoal(client,goalMsg2,callbackOpts);
cancelResponse = cancelAllGoalsAndWait(client)

cancelResponse = struct with fields:
              MessageType: 'action_msgs/CancelGoalResponse'
               ERROR_NONE: 0
           ERROR_REJECTED: 1
    ERROR_UNKNOWN_GOAL_ID: 2
    ERROR_GOAL_TERMINATED: 3
              return_code: 0
          goals_canceling: [1×1 struct]

Helper Functions

helperFeedbackCallback defines the callback function to execute when the client receives a feedback response from the action server.

function helperFeedbackCallback(goalHandle,feedbackMsg)
seq = feedbackMsg.partial_sequence;
disp(['Partial sequence feedback for goal ',goalHandle.GoalUUID,' is ',num2str(seq')])
end

helperCancelGoalCallback defines the callback function to execute when the client receives a cancel response after canceling a specific goal.

function helperCancelGoalCallback(goalHandle,cancelMsg)
code = cancelMsg.return_code;
disp(['Goal ',goalHandle.GoalUUID,' is cancelled with return code ',num2str(code)])
end

helperCancelGoalsCallback defines the callback function to execute when the client receives a cancel response after canceling a set of goals.

function helperCancelGoalsCallback(cancelMsg)
code = cancelMsg.return_code;
disp(['Goals cancelled with return code ',num2str(code)])
end

Input Arguments

client — ROS 2 action client

ros2actionclient object handle

ROS 2 action client, specified as a ros2actionclient object handle.

timestamp — Timestamp at or before which the goals sent by the action client must be cancelled

builtin_interfaces/Time message structure

Timestamp at or before which the goals sent by the action client must be cancelled, specified as a builtin_interfaces/Time message structure. You can use the ros2time function to create the message structure with a desired timestamp.

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• The callback functions used to send and cancel goals must be specified while creating the ros2actionclient object using these name-value arguments.

  • 'SendGoalOptions' — Specify a cell array of callback options structures for sending goals that you create using the ros2ActionSendGoalOptions function.

  • 'CancelFcn' — Specify the cancel response callback that you use with the cancelGoal function.

  • 'CancelAllFcn' — Specify the cancel response callback that you use with the cancelAllGoals function.

  • 'CancelBeforeFcn' — Specify the cancel response callback that you use with the cancelGoalsBefore function.

  Note that these arguments are used for definition of ros2actionclient only and must be specified again at the time of usage in the respective function.

  callbackOpts1 = ros2ActionSendGoalOptions(FeedbackFcn=@glfeedback,ResultFcn=@glResult);
  callbackOpts2 = ros2ActionSendGoalOptions(FeedbackFcn=@glfeedback2,ResultFcn=@glResult2);
  [client] = ros2actionClient(node,"my_action","my_action_type",SendGoalOptions={callbackOpts1,callbackOpts2},CancelFcn=@cancelGoalCB,CancelAllFcn=@cancelGoalsCB);
  goalMsg = ros2message(client);
  goalHandle = sendGoal(client,goalMsg,callbackOpts1);
  cancelGoal(client,goalHandle,CancelFcn=@cancelGoalCB);

Version History

Introduced in R2023a