start and stop rosbag within a python script

Question

Hi,

I wrote an Action Server which gets all topics I want to record via the goal. Everything works fine until i want to stop rosbag. With my script i can start rosbag out of my script and i can see the bag-file which is generated. But when i want to kill the rosbag process out of my script, rosbag doesn't stop. It doesn't stop until i stop my whole ActionServer. But the action server should still run after stopping rosbag.

Here is the code I wrote: (the topic_logger.msg includes the goal, an id and an array of topics)

#! /usr/bin/env python

import roslib; roslib.load_manifest('topic_logger')
import rospy
import subprocess
import signal

import actionlib

import topic_logger.msg

class TopicLoggerAction(object):
# create messages that are used to publish feedback/result
_feedback = topic_logger.msg.topicLoggerFeedback()
_result = topic_logger.msg.topicLoggerResult()

def __init__(self, name):
    self._action_name = name
    self._as = actionlib.SimpleActionServer(self._action_name, topic_logger.msg.TopicLoggerAction, execute_cb = self.execute_cb)
    self._as.start()
    rospy.loginfo('Server is up')

def execute_cb(self, goal):
    if goal.ID == "topicLog":
        # decide whether recording should be started or stopped
        if goal.command == "start":
            #start to record the topics
            rospy.loginfo('now the topic recording should start')
            args = ""               
            for i in goal.selectedTopics:
                args = args + " " + i
            command = "rosbag record" + args
            self.p = subprocess.Popen(command, stdin=subprocess.PIPE, shell=True, cwd=dir_save_bagfile)
            rospy.loginfo(self.p.pid)
            # process = p
            # print p.stdout.read()
            # check if the goal is preempted    
            while 1:
                if self._as.is_preempt_requested():
                    rospy.loginfo('Logging is preempted')
                    self._as.set_preempted()
                    break

        elif goal.command == "stop":
            #stop to record the topics
            rospy.loginfo('now the topic recording should stop')
            #self.p.send_signal(signal.SIGTERM)
            rospy.loginfo(self.p.pid)
            killcommand = "kill -9 " + str(self.p.pid)
            rospy.loginfo(killcommand)
            self.k = subprocess.Popen(killcommand, shell=True)
            
            rospy.loginfo("I'm done")
            #while 1:
            #   if self._as.is_preempt_requested():
            #       rospy.loginfo('Logging is preempted')
            #       self._as.set_preempted()
            #       break

        else:
            rospy.loginfo('goal.command is not valid')
    else:
        rospy.loginfo('goal.ID is not valid')

if __name__ == '__main__':
rospy.init_node('topicLogger')
dir_save_bagfile = '/home/ker1pal/'
TopicLoggerAction(rospy.get_name())
rospy.spin()

Are there any ideas why I can't stop rosbag out of my script without killing my whole ActionServer ?

Thanks Ralf

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Originally posted by r_kempf on ROS Answers with karma: 133 on 2011-07-25

Post score: 11

Answer 1

Ralf,

I'm just now playing around with actionlib, so I don't know if there are any other interactions, but I also recently wrote a node with starts recording data via rosbag and subprocess.Popen(). I've been ending the rosbag session with:

rosbag_proc = subprocess.Popen(...)
...
rosbag_proc.send_signal(subprocess.signal.SIGINT)

SIGINT is the same as "Ctrl-C" for Unix. It seems to end the rosbag process cleanly without adversely affecting my ROS node.

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Originally posted by heyneman with karma: 46 on 2011-07-26

This answer was ACCEPTED on the original site

Post score: 3

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Original comments

Comment by r_kempf on 2011-07-27:
I tried it bevor by sending such a signal but it doesn't help.what are the parameters you give to Popen?

Comment by rahvee on 2018-06-01:
When I end rosbag record by pressing Ctrl-C, it ends cleanly. But when I use subprocess.Popen and send_signal(signal.SIGINT), nothing happens (the child process doesn't stop recording). If I use SIGTERM, I end up with a filename.bag.active file, which is not good. :-(

Comment by Tones on 2019-04-15:
sending Ctrl-C to rosbag record seems to stop the main process, but the child processes seem to keep running. I could finish the recording properly by sending one more Ctrl-C to one of the subprocesses. An alternative is sending SIGINT to the complete process group.

Answer 2

Seems like

self.p = subprocess.Popen(command, stdin=subprocess.PIPE, shell=True, cwd=dir_save_bagfile)

starts a shell which then starts the program that does the job. One could see it with ps:

$ ps aux | grep record
sergey   17900  0.0  0.0   4272   584 pts/4    S    18:36   0:00 /bin/sh -c rosbag record -O /home/ . . . 
sergey   17901  7.3  0.1 288132  7124 pts/4    Sl   18:36   0:00 record --buffsize 256 -O /home/ . . . 

Therefore killing the process with pid returned by subprocess.Popen does not kill the actual bag recording. We also need to kill its child. There is a nice code snippet here for kill_child_processes(). Here is my modified version:

import subprocess, os, signal

def terminate_process_and_children(p):
    ps_command = subprocess.Popen("ps -o pid --ppid %d --noheaders" % p.pid, shell=True, stdout=subprocess.PIPE)
    ps_output = ps_command.stdout.read()
    retcode = ps_command.wait()
    assert retcode == 0, "ps command returned %d" % retcode
    for pid_str in ps_output.split("\n")[:-1]:
            os.kill(int(pid_str), signal.SIGINT)
    p.terminate()

This function expects a subprocess.Popen object.

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Originally posted by sergey_alexandrov with karma: 260 on 2012-04-11

This answer was NOT ACCEPTED on the original site

Post score: 10

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Original comments

Comment by bchr on 2014-12-05:
Works for me!

Comment by RafBerkvens on 2015-01-30:
I don't fully understand it, but it works for me!

Comment by vorilant on 2016-07-28:
Thank you so much! Been looking for hours for something that did this. And the built in kill commands from subprocess refused to kill the child of rosbag play

Answer 3

I was recently looking for solving the same issue and thought I would add my experience as this thread didn't have an answer that solved my problem.

The issue I was seeing was that rosbag would not clean exit, and thus write the .bag.active -> .bag file. Sending SIGINT, SIGKILL, etc.. in any order to the processes could not remedy the situation on my system.

Using rosnode I was able to kill the rosbag and have it cleanly exit. This would be more difficult when running multiple rosbag records at once (as you would need to find the rosnode id of each), however with only one running rosbag record, simply using 'rosnode list' to search for "/record_xxxx" and then executing "rosnode kill /record_xxxx" where xxx is the node id will cleanly exit the rosbag recording process.

def terminate_ros_node(s):
    list_cmd = subprocess.Popen("rosnode list", shell=True, stdout=subprocess.PIPE)
    list_output = list_cmd.stdout.read()
    retcode = list_cmd.wait()
    assert retcode == 0, "List command returned %d" % retcode
    for str in list_output.split("\n"):
        if (str.startswith(s)):
            os.system("rosnode kill " + str)

terminate_ros_node("/record")

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Originally posted by schadlerm with karma: 86 on 2013-12-06

This answer was NOT ACCEPTED on the original site

Post score: 5

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Original comments

Comment by fapofa on 2013-12-08:
Hi schadlerm!

Thanks for sharing this info. I am running into the same problem, with C implementation. I am trying to launch and kill with SIGINT rosbag from C application. The main problem is that sometimes I end up with un-indexed bagfile. If you have any idea for this, I would appreciate it.

Comment by Femer on 2017-04-28:
This was extremely useful! I created a simple gist as an example: example rosbag_record.py

Comment by adamconkey on 2018-05-31:
Yours is the only solution that worked for me here, though I modified line 7 to be if (str.startswith(s + "_") or str == s): because the node that publishes to rosout is called "/recorder", so yours will probably try to kill that node also.

Answer 4

Similar to sergey_alexandrov answer, but using psutils python module as highlight on stackoverflow : http://stackoverflow.com/questions/3332043/obtaining-pid-of-child-process

def terminate_process_and_children(p):
  import psutil
  process = psutil.Process(p.pid)
  for sub_process in process.get_children(recursive=True):
      sub_process.send_signal(signal.SIGINT)
  p.wait()  # we wait for children to terminate
  p.terminate()

def main():
  dir_save_bagfile = '/tmp/'
  rosbag_process = subprocess.Popen('rosbag record -a -j -o {}'.format("my_rosbag_prefis"), stdin=subprocess.PIPE, shell=True, cwd=dir_save_bagfile)
  terminate_process_and_children(rosbag_process)

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Originally posted by lgeorge with karma: 123 on 2016-01-07

This answer was NOT ACCEPTED on the original site

Post score: 4

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Original comments

Comment by Felix Widmaier on 2017-08-10:
I had to change process.get_children to process.children and remove the p.terminate() (process is already gone at that point) but after that it is working.

Comment by canderson on 2019-09-16:
Yeah agreed with @Felix Widmaier here that this snippet doesn't quite work as described

Answer 5

Picking from many of the answers here, I've come up with a class and ROS node to control recording start, stop and pause. Find it here.

You can either import the class and use it directly in your code or start the node standalone and use service calls to control recording.

There is a problem with pausing where, sometimes, some of the messages get their timestamps wrong after resuming recording. Unfortunately, I don't have the time to debug it now. Start and stop seem to work fine.

Tested with Ubuntu 16 and Kinetic.

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Originally posted by vbs with karma: 62 on 2020-09-12

This answer was NOT ACCEPTED on the original site

Post score: 3