[ros-users] ROS nodes & SIGINT handler

[Kevin Watts]

This isn't an answer to the "can nodes launch other nodes" question, but you
can use a mux to turn on and off the recording. Just set the mux to publish
to the output topic when you're flying, and disable it when you land.

The only downside is that all flights will be combined into the same
bagfile.

http://www.ros.org/wiki/topic_tools/mux

Kevin

On Tue, Aug 31, 2010 at 12:06 PM, Gautier Dumonteil <
gautier.dumonteil at gmail.com> wrote:

>  Hi users,
>
> In our reseach project, we would like to be able to record bags
> "automatically" (e.g recording when our UAV is flying).
> So, I'm trying to write a simple node (*recorder_interface*) with two
> services "start_record" and "stop_record", where "start_record" callback
> launch the rosbag::recorder::run() in a child process using fork(). The
> "stop_record" callback just sends the SIGINT signal to recorder PID to stop
> recording ... but nothing happen. It seems that the ROS node forked doesn't
> handle SIGINT signals.
>
> Also, when checking available nodes with "rosnode list", I've only the *
> recorder_interface* node. I should have also something like
> "record_1283279499007996727", which is the rosbag record node.
>
> I'm wondering if a node can launch others nodes??
>
> Here, the console output and code:
>
> [ INFO] [1283279481.648585599]: Recorder_interface spinning: ready to
> record.
> [ INFO] [1283279499.006083281]: Request to record topics: test
> [ INFO] [1283279499.007996722]: Child: pid = 10497
>
> [ INFO] [1283279499.008979878]: Subscribing to /fake_alti
> [ INFO] [1283279499.009749320]: Recording to test_2010-08-31-14-31-39.bag.
>
> #include <signal.h>
> #include "ros/ros.h"
> #include "recorder_interface/rec_interface.h"
> #include "rosbag/recorder.h"
> #include "rosbag/exceptions.h"
>
> bool  recording;
> int   recorder_exit_code;
> pid_t rosbag_pid;
>
> void rosbagRecord (rosbag::RecorderOptions opts)
> {
>     char ** argv = NULL;
>     int argc=0;
>     ros::init(argc, argv, "record", ros::init_options::AnonymousName);
>
>     // **** Run the recorder
>     rosbag::Recorder recorder(opts);
>     recorder_exit_code = recorder.run();
>     ROS_INFO("recorder_exit_code: %d\n",recorder_exit_code);
> }
>
> bool startRec(recorder_interface::rec_interface::Request &req,
>                   recorder_interface::rec_interface::Response &res)
> {
>     if(!recording)
>     {
>         recording=true;
>         ROS_INFO("Request to record topics: %s", req.topics.c_str ());
>
>         // **** Fill rosbag options
>         rosbag::RecorderOptions opts;
>         opts.record_all = false;
>         opts.quiet = true;
>         opts.prefix = req.prefix;
>         opts.append_date = true;
>         opts.topics.push_back("/fake_alti");
>
>         rosbag_pid = fork();
>         if(rosbag_pid == -1)
>         {
>             // **** ouch, fork() failed
>             perror("fork");
>             exit(-1);
>         }
>         else if(rosbag_pid == 0)
>         {
>             // **** child
>             ROS_INFO("Child: pid = %d\n", (int)getpid());
>             rosbagRecord(opts);
>             exit(-1);
>         }
>     }
>     else
>     {
>         ROS_WARN("Already recording!");
>     }
>    return true;
> }
>
>
> bool stopRec(recorder_interface::rec_interface::Request &req,
>                   recorder_interface::rec_interface::Response &res)
> {
>    if(recording)
>     {
>         int err = kill(rosbag_pid, SIGINT);
>         ROS_INFO("err = %d\n",err);
>         if(err==0)
>         {
>             res.ans=recorder_exit_code;
>             recording=false;
>         }
>     }
>     else
>     {
>         ROS_WARN("Not recording!");
>     }
>    return true;
> }
>
> int main(int argc, char **argv)
> {
>   recording=false;
>
>   ros::init(argc, argv, "recorder_interface");
>   ros::NodeHandle n;
>
>   ros::ServiceServer serviceStart,serviceStop;
>   serviceStart = n.advertiseService("start_record", startRec);
>   serviceStop = n.advertiseService("stop_record", stopRec);
>   ROS_INFO("Recorder_interface spinning: ready to record.");
>   ros::spin();
>   return 0;
> }
>
>
>
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>
>
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