ROS node name duplicate

scene :ROS The node created in has a name ,C++ Initialize the node by API:ros::init(argc,argv,"xxxx"); To define the node name , stay Python The initialization node in is through  rospy.init_node("yyyy")  To define the node name . stay ROS Network topology , Nodes with duplicate names cannot appear , Because it is assumed that duplicate names can exist , Then there will be confusion when calling , That means , You cannot start a node with the same name or start the same node multiple times , You bet , stay ROS If you start the node with the same name , Previously existing nodes will be closed directly , But if there is such a need , How to optimize ？

stay ROS The solution strategy given in is to use Namespace or name remapping .

A namespace is a prefix to a name , Name remapping is aliasing a name . Both of these strategies can solve the problem of node name duplication , There are many ways to realize the two strategies :

• rosrun command
• launch file
• coded

All of the above three ways can be through namespace or name remapping , To avoid duplicate node names , This section will demonstrate the use of the three one by one , The requirements of the three are similar .

Case study

Start two turtlesim_node node , Of course, if you directly open two terminals , Direct start , Then the node that is started for the first time will shut down , And give tips :

[ WARN] [1578812836.351049332]: Shutdown request received.
[ WARN] [1578812836.351207362]: Reason given for shutdown: [new node registered with same name]

 1 rosrun Set namespace and remap

1.rosrun Set namespace

1.1 Set namespace presentation

grammar : rosrun Package name The node name __ns:= New name

rosrun turtlesim turtlesim_node __ns:=/xxx
rosrun turtlesim turtlesim_node __ns:=/yyy

example

rosrun turtlesim turtlesim_node __ns:=ergouzi
rosrun turtlesim turtlesim_node __ns:=maolvzi

  Both nodes can operate normally

1.2 Running results

[email protected]:~$ rosnode list
/ergouzi/turtlesim
/first/my_turtle
/maolvzi/turtlesim
/my_turtle
/rosout
/second/my_turtle

2.rosrun Name remapping

2.1 Alias the node

grammar : rosrun Package name The node name __name:= New name

rosrun turtlesim turtlesim_node __name:=t1

rosrun turtlesim turtlesim_node __name:=t2

example

rosrun turtlesim turtlesim_node __name:=daqiang

rosrun turtlesim turtlesim_node __name:=xiaoqiang

 2.2 Running results

rosnode list View node information , Show results :

[email protected]:~$ rosnode list
/daqiang
/xiaoqiang

3.rosrun Namespace and name remapping overlay

3.1 The namespace name is also remapped

grammar : rosrun Package name The node name __ns:= New name __name:= New name

rosrun turtlesim turtlesim_node __name:=daqiang __ns:=ergouzi

rosrun turtlesim turtlesim_node __name:=xiaoqiang __ns:=maolvzi

[email protected]:~$ rosnode list
/ergouzi/daqiang
/rosout
/maolvzi/xiaoqiang

 2 launch File set namespace and remap

Introduce launch When using the syntax of the file , stay node There are two properties in the tag : name and ns, They are used to realize name remapping and namespace setting respectively . Use launch It is also relatively simple to remap file namespace and name .

1.launch file

Create a new function pack rename01_node, Then create a new launch Folder , New under this path start_turtle.launch

<!--  Need to start multiple turtles GUI node  -->
<launch>
    <node pkg="turtlesim" type="turtlesim_node" name="turtlesim" />
    <!--   Name remapping  -->
    <node pkg="turtlesim" type="turtlesim_node" name="t1" />
    <!--  Namespace  -->
    <node pkg="turtlesim" type="turtlesim_node" name="turtlesim" ns="ergouzi" />
    <!--  Namespace  +  Name remapping  -->
    <node pkg="turtlesim" type="turtlesim_node" name="t2" ns="maolvzi" />
    
</launch>

roscore

roslaunch renaame01_node start_turtle.launch

 

 3 Encoding setting namespace and remapping

If the custom node implements , Then you can set the namespace and remap more flexibly .

1.C++ Realization : Remap

1.1 Name alias settings

Core code  ros::init(argc,argv,"zhangsan",ros::init_options::AnonymousName);

 1.2 perform

Time stamp will be added after the name .

2.C++ Realization : Namespace

2.1 Namespace settings

Core code

  std::map<std::string, std::string> map;
  map["__ns"] = "xxxx";
  ros::init(map,"wangqiang");

2.2 perform

The node name has a namespace .