[ros-users] Problems with rosbags in Electric on Oneiric

[Hordur Johannsson]

On Sun, 2011-10-30 at 09:45 -0700, Bhaskara Marthi wrote:
> This seems to be a general problem, not just on Oneiric, with rosbag
> on electric.  A ticket has been created at
> https://code.ros.org/trac/ros/ticket/3727.
> - Bhaskara
I opened this ticket https://code.ros.org/trac/ros/ticket/3709 a while
ago. The rosbag in Electric creates a new connection for each message.
If you are recording large bag files I would avoid using Electric
and switch to Diamondback. Otherwise you end up with a bag file that
takes very long to load, e.g. I had a file with 1 million messages and
gave up after having waited for an hour.

A part of the problem is also they way rosbag play works. It scans 
the whole file looking into the index for each chunk. Each chunk is 
around 1MB so a 30GB would require 3000 seeks which take ~2min. So
you would have to wait few minutes before seeing the first message.
The second problem is that before playing rosbag play iterates through
all the connections and finding connections that match the query
settings. When you log using Electric you might have a lot of 
those (1 per message).

It might be useful to create a version of rosbag that is tuned to
quick startup and processes queries and chunk headers as they are
encountered.

Thanks,
Hordur

> 
> On Sun, Oct 30, 2011 at 9:24 AM, Ahlberg Rasmus
> <rasmus.ahlberg at combitech.se> wrote:
> > Hi,
> > I managed to install the Electric version of ROS on Oneiric by using the
> > Natty repo. However, my rosbag recordings are much larger than they used to
> > be. Also, running "rosbag info" on them takes 10-15 seconds instead of being
> > almost instantaneous. Has anyone else experienced this problem?
> >
> > I've noticed that there seems to be one connection per message, according to
> > the "rosbag info" printout. Previously in Diamondback+Natty I only had 5 or
> > so, even if there were several thousands of messages. Now they match
> > one-to-one. Is this normal in Electric?
> >
> > Didn't want to put up a question on answers.ros.org, as I assume this isn't
> > a supported setup.
> >
> > Regards,
> > Rasmus Ahlberg
> >
> >
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> >
> 
> 
>