[ros-users] Question about roslaunch and remote processes.

[Tully Foote]

Hi,

Good questions.  In the future these are great questions for answers.ros.org.
If you wouldn't mind reasking them there I'd be happy to copy my answers
there too.  That forum provides a easier way to search and browse previously
asked questions.  And helps identify duplicate questions.


Meanwhile, answers inline.

On Mon, Jul 25, 2011 at 10:50 AM, Joan Pau Beltran
<joanpau.beltran at uib.cat>wrote:

> Hi everyone,
>
> I have to questions about roslaunch and remote processes that seem to
> point some bugs out.
> We are using Diamondback as current release.
>
> Firstly, the output=screen attribute seems to be ignored, since I don't
> get any output with lines like:
> > <launch>
> > <node machine="fugu-c" pkg="memsense_imu" type="imu_node"
> > name="imu_node" output="screen">
> > <rosparam file="$(find fugu_configurations)/imu/params.yaml" />
> > <param name="frame_id" value="imu" />
> > </node>
> > </launch>
> I am sure (because I wrote it myself) that the node is using the
> rosconsole macros for output. According to the wiki, one of the reasons
> to use the macros instead of the standard c++ streams is the possibility
> to get output from remotely launched processes. Does anyone know what
> may be happening?
>

Console outputs from remote machines are not displayed.  To view the
rosconsole macro outputs I recommend using the rxconsole
http://www.ros.org/wiki/rxconsole It is the best way to take advantage of
the powerful logging macros throughout the system.


> The machine file looks like this:
> > <launch>
> > <machine name="fugu-c" address="fugu-c.local" user="user"
> >     ros-root="/opt/ros/diamondback/ros/"
> >     ros-package-path="/home/user/ros:/opt/ros/diamondback/stacks" />
> > </launch>
>
>
> And the second one, it seems that the roslaunch mechanism does not
> honour the ROS_HOSTNAME variable for remote machines. In the .bashrc
> file of the remote machine this variable is set to 'fugu-c.local', to
> allow the remote machine name to be resolved properly using Avahi (that
> seems to become quite standard in the latest distributions, this is the
> reason for the .local suffix).
> However when launching the above file, connection is stablished with the
> remote machine, even the core is found if running there, but any node is
> launched. This is the output:
> > started roslaunch server http://10.42.43.1:51495/
> > remote[fugu-c.local-0] starting roslaunch
> > remote[fugu-c.local-0]: creating ssh connection to fugu-c.local:22,
> > user[user]
> > remote[fugu-c.local-0]: ssh connection created
> >
> > SUMMARY
> > ========
> >
> > PARAMETERS
> >  ...
> > MACHINES
> >  * fugu-c
> >
> > NODES
> >   /
> >     imu_node (memsense_imu/imu_node)
> >
> > ROS_MASTER_URI=http://fugu-c.local:11311
> >
> > core service [/rosout] found
> > error launching on [fugu-c.local-0, uri http://fugu-c:39451/]: Name or
> > service not known
> > Launch of the following nodes most likely failed: memsense_imu/imu_node
> Apparently, the uri is computed as the result of the hostname command on
> the remote machine, which returns only 'fugu-c' instead of
> 'fugu-c.local'. I expected that setting the ROS_HOSTNAME would overwrite
> this behaviour (actually it works for finding the remote core). If this
> is a bug or a possible improvement, where should I submmit it? If not,
> any idea on how to handle this? By now, we added the corresponding entry
> to /etc/hosts to overcome the problem, but I would expect a better
> solution.
>

For the environment variables see this discussion.
https://code.ros.org/lurker/message/20090301.023742.7fc6cb7b.en.html

ROS does expect that your machines are setup correctly to talk to each other
by hostname, setting it in /etc/hosts is a common local patch.
http://www.ros.org/wiki/ROS/NetworkSetup

Tully

>
>
> Thank you in advance!
>
> --
> Joan Pau Beltran
> Grup de Sistemes, Robòtica i Visió - DMI
> Universitat de les Illes Balears
>
> _______________________________________________
> ros-users mailing list
> ros-users at code.ros.org
> https://code.ros.org/mailman/listinfo/ros-users
>



-- 
Tully Foote
Systems Engineer
Willow Garage, Inc.
tfoote at willowgarage.com
(650) 475-2827
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