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Altering liveliness lease_duration #755

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Altering liveliness lease_duration #755

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2168603
altering announcement_period
CursedRock17 May 2, 2024
3f932d2
altering announcement_period
CursedRock17 May 2, 2024
ffb4386
Typo causing error fix
CursedRock17 May 3, 2024
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2 changes: 1 addition & 1 deletion rmw_fastrtps_shared_cpp/src/qos.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -141,7 +141,7 @@ bool fill_entity_qos_from_profile(
// Docs suggest setting no higher than 0.7 * lease_duration, choosing 2/3 to give safe buffer.
// See doc at https://github.com/eProsima/Fast-RTPS/blob/
// a8691a40be6b8460b01edde36ad8563170a3a35a/include/fastrtps/qos/QosPolicies.h#L223-L232
double period_in_ns = entity_qos.liveliness().lease_duration.to_ns() * 2.0 / 3.0;
int64_t period_in_ns = entity_qos.liveliness().lease_duration.to_ns() * 2 / 3;
double period_in_s = RCUTILS_NS_TO_S(period_in_ns);
Comment on lines +144 to 145
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Just coming back to look at this again, and I'm realizing that these two lines together are wrong, at least, with the current implementation of RCUTILS_NS_TO_S.

The problem is in switching period_in_ns to an int64_t. Because RCUTILS_NS_TO_S currently uses longs in the divisor, then everything is an integer. So if you have less than 1 second (1000000000 ns), then we use integer division here and always end up with zero. That's likely why period_in_ns was a double to begin with, since everything will be promoted to a double.

If we put in ros2/rcutils#460 along with this one, then I guess that particular issue goes away. But this is making me much more nervous about ros2/rcutils#460 in general. While this macro isn't used very heavily, I think that will change the semantics enough that it is concerning. I'll leave a comment over there.

As far as this PR goes, I actually think that what is here is fine, at least for now. So I'm actually going to suggest that we close this PR out.

entity_qos.liveliness().announcement_period = eprosima::fastrtps::Duration_t(period_in_s);
}
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