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

Damon Kohler damonkohler at google.com
Thu Jun 23 19:01:36 UTC 2011 

Thanks, Nicholas.

That is the approach I will take.

Damon

On Wed, Jun 22, 2011 at 4:48 PM, Nicholas Butko <nbutko at ucsd.edu> wrote:
> Damon,
> One option is to take the course of "When in doubt, follow the behavior of
> roscpp." In that case, when a second node registers with the same name, the
> first node dies. For example, if you run
> {{{
> rosrun roscpp_tutorials talker
> }}}
> twice, the second instance behaves normally, but the first instance shows
> {{{
> [ INFO] [1308753854.115622000]: hello world 72
> [ INFO] [1308753854.215643000]: hello world 73
> [ WARN] [1308753854.285720000]: Shutdown request received.
> [ WARN] [1308753854.285791000]: Reason given for shutdown: [new node
> registered with same name]
> [ INFO] [1308753854.315770000]: hello world 74
> }}}
> Just a thought. What do you think?
> --Nick
>
> On Wed, Jun 22, 2011 at 7:03 AM, Damon Kohler <damonkohler at google.com>
> wrote:
>>
>> 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
>> >>>
>> >>> _______________________________________________
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>> >>> https://code.ros.org/mailman/listinfo/ros-users
>> >>>
>> >>
>> >>
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>>
>>
>> --
>> ----------------------------------------------
>> Damon Kohler
>> Software Engineer
>>
>> Google Germany GmbH
>> Dienerstr. 12
>> 80331 München
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>> AG Hamburg, HRB 86891
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>> Geschäftsführer: John Herlihy, Graham Law, Lloyd Martin, Kent Walker
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-- 
----------------------------------------------
Damon Kohler
Software Engineer

Google Germany GmbH
Dienerstr. 12
80331 München
----------------------------------------------
AG Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg
Geschäftsführer: John Herlihy, Graham Law, Lloyd Martin, Kent Walker
----------------------------------------------
Diese E-Mail ist vertraulich. Wenn Sie nicht der richtige Adressat
sind, leiten Sie diese bitte nicht weiter, informieren den Absender
und löschen Sie die E-Mail und alle Anhänge. Vielen Dank.

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