[ros-users] rosjava Exception if create two Nodes with same name

[Damon Kohler]

So, I can explain what's going on, but I'll have to think about what
the correct behavior should be. Please file an issue about this.

Basically, the exception that's being thrown is correct. You should
not try to register two nodes with the same name.

The reason it still works is that you don't _have_ to register a
subscriber in order to connect it to a publisher. At the point the
exception is thrown, the subscriber has enough information to connect
to the publisher.

Because the master registration happens asynchronously, it doesn't
affect your ability to connect to the publisher. To do that, we'd
either have to wait for registration to succeed, or disconnect you
some time in the future if it failed. Both of those options are pretty
terrible.

Damon

On Tue, Jun 21, 2011 at 8:25 PM, Abhishek Verma
<toabhishekverma at gmail.com> wrote:
> How about remote subscribers ?
> I dont know if this use case exist or not but There can be remote
> publisher/subscriber?
> What happens in c++? Do code core refuse connection?
>
> Rosjava need fix ...I am seeing this exception but publisher and subscriber
> are able to communicate..(with exception)
>
>
> Thanks and Regards
> Abhishek Verma
>
>
> On Tue, Jun 21, 2011 at 6:41 PM, Nicholas Butko <nbutko at ucsd.edu> wrote:
>>
>> ROS nodes must have unique names. Two start two nodes of the same type in
>> c++, you would use the command line arguments to set the name of the nodes,
>> which would override the default.
>> I'm not sure if this command line argument name remapping was implemented
>> in java, but if it wasn't, you may consider having java append a random
>> number to the end of the node name.
>> --Nick
>> On Tue, Jun 21, 2011 at 10:33 AM, Abhishek Verma
>> <toabhishekverma at gmail.com> wrote:
>>>
>>> Hi Friends,
>>> I am seeing following exception
>>> 21-Jun-2011 18:29:01 org.apache.xmlrpc.server.XmlRpcErrorLogger log
>>> SEVERE: Failed to invoke method registerSubscriber in class
>>> org.ros.internal.node.xmlrpc.MasterImpl: null
>>> org.apache.xmlrpc.common.XmlRpcInvocationException: Failed to invoke
>>> method registerSubscriber in class org.ros.internal.node.xmlrpc.MasterImpl:
>>> null
>>> at
>>> org.apache.xmlrpc.server.ReflectiveXmlRpcHandler.invoke(ReflectiveXmlRpcHandler.java:129)
>>> at
>>> org.apache.xmlrpc.server.ReflectiveXmlRpcHandler.execute(ReflectiveXmlRpcHandler.java:106)
>>> at
>>> org.apache.xmlrpc.server.XmlRpcServerWorker.execute(XmlRpcServerWorker.java:46)
>>> at org.apache.xmlrpc.server.XmlRpcServer.execute(XmlRpcServer.java:86)
>>> at
>>> org.apache.xmlrpc.server.XmlRpcStreamServer.execute(XmlRpcStreamServer.java:200)
>>> at org.apache.xmlrpc.webserver.Connection.run(Connection.java:208)
>>> at org.apache.xmlrpc.util.ThreadPool$Poolable$1.run(ThreadPool.java:68)
>>> Caused by: java.lang.IllegalStateException
>>> at
>>> com.google.common.base.Preconditions.checkState(Preconditions.java:129)
>>> at
>>> org.ros.internal.node.server.MasterServer.addSlave(MasterServer.java:80)
>>> at
>>> org.ros.internal.node.server.MasterServer.registerSubscriber(MasterServer.java:110)
>>> at
>>> org.ros.internal.node.xmlrpc.MasterImpl.registerSubscriber(MasterImpl.java:123)
>>> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>>> at
>>> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
>>> at
>>> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
>>> at java.lang.reflect.Method.invoke(Method.java:597)
>>> at
>>> org.apache.xmlrpc.server.ReflectiveXmlRpcHandler.invoke(ReflectiveXmlRpcHandler.java:115)
>>>
>>> My code is
>>> //Publisher
>>> node = new Node("Camera1", configuration);
>>> publisher = node.createPublisher("Camera1",
>>> org.ros.message.sensor_msgs.Image.class);
>>> ....................
>>> //Subscriber
>>>  node = new Node("Camera1", configuration);
>>>       System.out.println("ScreenView.main() Starting");
>>> //      final Log log = node.getLog();
>>>       node.createSubscriber("Camera1", new
>>> MessageListener<org.ros.message.sensor_msgs.Image>() {
>>>         public void onNewMessage(org.ros.message.sensor_msgs.Image
>>> message) {
>>>           System.out
>>> .println("Subscriber \"" + message + "\"");
>>>         }
>>>       }, org.ros.message.sensor_msgs.Image.class);
>>>
>>> Reason behind this exception is Nodes with same name.
>>> If I change this name and create different nodes in publisher and
>>> subscribers code then its fine.
>>> Anyone has any idea why is that or we are not supposed to create node
>>> with same name?
>>> Thanks and Regards
>>> Abhishek Verma
>>>
>>> _______________________________________________
>>> ros-users mailing list
>>> ros-users at code.ros.org
>>> https://code.ros.org/mailman/listinfo/ros-users
>>>
>>
>>
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-- 
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Damon Kohler
Software Engineer

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