add get_publishers_info_by_topic

[NerdToMars]

related issue: #78

[m-dahl]

Sorry for the delay I was caught up in the holiday season. I think this looks ready to merge once we fix the CI (looks like a type change should do it) and rebase on top of master.

[NerdToMars]

Sorry for the delay I was caught up in the holiday season. I think this looks ready to merge once we fix the CI (looks like a type change should do it) and rebase on top of master.

thanks for helping review, I updated PR, but I still has this error for foxy:
seems the time is point to some address has sec: 7FFFFFFF, nsec: FFFFFFFF,

thread 'tokio_testing' panicked at r2r/tests/tokio_testing.rs:152:16:
called `Result::unwrap()` on an `Err` value: JoinError::Panic(Id(3), ...)
from_rmw_time_t rmw_time_t { sec: 2147483647, nsec: 4294967295 }
thread 'tokio-runtime-worker' panicked at r2r/src/qos.rs:829:9:
nsec part of rmw_time_t should be less than 1 billionthread 'tokio_testing' panicked at r2r/tests/tokio_testing.rs:152:16:
called `Result::unwrap()` on an `Err` value: JoinError::Panic(Id(3), ...)
from_rmw_time_t rmw_time_t { sec: 2147483647, nsec: 4294967295 }
thread 'tokio-runtime-worker' panicked at r2r/src/qos.rs:829:9:
nsec part of rmw_time_t should be less than 1 billion

full error can be found here: https://github.com/NerdToMars/r2r/actions/runs/7463328195/job/20307738761

I have checked the foxy rmw implementation, and it seems same as others DISTRO, https://github.com/ros2/rmw/blob/7fa45cb0d86fef00488e707b9ef37914d7ff0369/rmw/include/rmw/types.h#L321

Do you have any suggestions?

[m-dahl]

Hi,

This commit looks to be from some months after the one you linked: ros2/rmw@703992c

There is a comment added about RMW_DURATION_INFINITE which seem to hint that the previous behaviour (which would be in foxy) was not standardized between rmw implementations. I would guess that the behaviour changed between foxy and galactic and that in foxy an unspecified time was represented as you found.

We could just add a conditional compilation for #[cfg(r2r__ros__distro__foxy)] that checks for the constant and turns it into a zero duration.

But maybe we also need to handle RMW_DURATION_INFINITE in some way?

[NerdToMars]

Thanks for helping look into this, I tried to use ros2cli to publish some dummy std_msgs/msg/String topic without explicitly specify its qos profile, then I use ros2cli to get the verbose info of this dummy topic, I noticed all the duration data in the qos profile is like:

sec: 2147483651294967295 ( 2,147,483,647,000,000,000 + 4,294,967,295 )  nanosecs
nsec: 2147483651294967295 ( 2,147,483,647,000,000,000 + 4,294,967,295 ) nanosecs

which is similar as someone mentioned here ros2/rmw#210 (comment).
I noticed Foxy publisher is using #define RMW_QOS_DEADLINE_DEFAULT {0, 0} as deadline in default QoS profile, but somehow the subscriber is getting different deadline duration results (2147483651294967295). Sadly I did not find the corresponding implementation for this kind of behavior.

[m-dahl]

Well at least it fixed CI :) Perhaps the proper fix is to simply drop foxy support with the next release, I am not sure if anyone would care now that it's so old(?). Will merge this now, thanks for your contribution.