Datarace in SimpleActionClient if /use_sim_time is used

[1r0b1n0]

Hello,

I stumbled on a datarace bug in the ActionClient class when using actionlib in a Gazebo simulation (thus having /use_sim_time=true, and an external node that publishes the /clock topic).

To be able to reproduce the bug I created two simple roslaunch files here : https://github.com/1r0b1n0/actionlib_sim_time_datarace_test
On my system, more or less 1 out of 5 times starting the fibonacci_client node will fail and return immediately.

I uploaded the log of fibonacci_client here : https://github.com/1r0b1n0/actionlib_sim_time_datarace_test/blob/master/fibonacci_client_bug.log

This is what happened :

1. fibonacci_client calls ros::init(...), /use_sim_time is true so ros will subscribe to /clock (in its internal thread)
2. One second later fibonacci_client calls ac.waitForResult(ros::Duration(30.0))
   In SimpleActionClient::waitForResult(ros::Duration &) , we have the instruction :
   ros::Time timeout_time = ros::Time::now() + timeout; (simple_action_client:551)
   Sometimes this instruction is called when ros has not yet received the /clock topic from Gazebo, so ros::Time::isValid() is false, and ros::Time::now() will return ros::Time(0,0)
3. some milliseconds later, ros has received its first /clock from Gazebo ( in this case /clock is at 1271.800000000), so ros::Time::now() will return ros::Time(127.8) -> SimpleActionClient will timeout and return immediately

A solution would be to call ros::Time::waitForValid() in ActionClient::waitForActionServerToStart()

Thanks,
Robin

[mikaelarguedas]

@1r0b1n0 Did #59 fix this issue ?
It looks like I can still reproduce it locally around 1/15 times

[1r0b1n0]

Indeed in some cases I still had some issues (but like 1 out of 200 times).
Because the application is multi-threaded, we should also wait for ros:Time::now to become valid when constructing ConnectionManager
I submitted #62 that fixes those issues for me, does it work on your side ?

[mikaelarguedas]

fixed by #59 and #62. Feel free to reopen or create another issue if the problem reappears