Stop sensor subscribe-check timer once subscribed (fix #23 rmw_zenoh ERROR spam)

[rolker]

Summary

SensorBase::subscribeCheck() was written for ROS 1's one-shot ros::Timer, but the ROS 2 port uses rclcpp::create_wall_timer — which always repeats (create_timer.hpp only takes autostart; no one-shot option exists in rclcpp). The original comment // subscribed, so bail out before setting a new timer describes semantics the new timer no longer has, so once a sensor subscribed, the 1 s check timer kept firing and subscribe() recreated subs_.imu / subs_.navsat_fix / etc. every tick. Under rmw_zenoh_cpp the per-second teardown raced in-flight samples, producing the sporadic ERROR logs reported in #23:

[mru_transform_node-1] [ERROR] [rmw_zenoh_cpp]: SubscriberCallback triggered over 0/bizzy/mavros/imu/data/sensor_msgs::msg::dds_::Imu_/RIHS01_…

The defect was latent since the ROS 2 port; the previous DDS RMW didn't log the teardown race, so it only became visible after the late-Apr-2026 Zenoh migration.

Changes

• SensorBase::subscribeCheck() (mru_transform/include/mru_transform/sensor.hpp): restructured into early-returns on the not-ready paths (the single repeating constructor timer keeps polling) and subscribe_check_timer_->cancel() once subscribed. Cancelling a timer inside its own callback is the standard rclcpp one-shot idiom. One fix in the base covers all three sensor types.
• subscribe() guards in orientation_sensor.cpp, position_sensor.cpp, velocity_sensor.cpp: early-return true if any of that sensor's subs_ members is already set. Defense-in-depth — with the timer cancel, subscribe() is normally never re-entered, but the guard prevents any future regression from tearing down a live subscription.
• New regression test test/test_subscribe_once.cpp: drives a real OrientationSensor with a live publisher on the configured topic, spins past several timer periods, and asserts subscribe() runs exactly once and the check timer is cancelled. Verified to fail on the pre-fix code (subscribe call count climbs ~1 Hz) and pass after the fix.

Behavior note (intentional)

This restores the original "subscribe once to the first supported type, then stop" semantics. A topic publisher that later switches to a different supported type (e.g. Imu → QuaternionStamped) will not be re-evaluated. That matches the ROS 1 behavior and the existing design; if dynamic type-switching on a live topic is ever wanted, please open a separate issue.

Test plan

• colcon build (worktree): mru_transform builds cleanly.
• colcon test: 9 tests, 0 failures (including the new test_subscribe_once).
• Regression test verified to fail on the pre-fix code (stashed sensor.hpp revert) and pass with the fix restored.
• Field validation: confirm the SubscriberCallback triggered over … ERROR spam stops in a fresh run of mru_transform_node against /bizzy/mavros/imu/data under rmw_zenoh.

Closes #23

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Authored-By: Claude Code Agent
Model: Claude Opus 4.7 (1M context)

[Copilot]

Pull request overview

This PR fixes issue #23 by restoring subscribe-once behavior for sensor topic detection in the ROS 2 port, preventing repeated subscription teardown/recreation and the resulting rmw_zenoh_cpp error spam.

Changes:

• Cancels SensorBase’s polling timer after a successful subscription while keeping retry polling for unknown/unsupported topics.
• Adds already-subscribed guards to orientation, position, and velocity sensor subscription methods.
• Adds a regression test that verifies subscribe() runs once and the check timer stops.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
mru_transform/include/mru_transform/sensor.hpp	Stops the repeating subscribe-check timer after successful subscription.
mru_transform/src/orientation_sensor.cpp	Avoids recreating an existing orientation subscription.
mru_transform/src/position_sensor.cpp	Avoids recreating an existing position subscription.
mru_transform/src/velocity_sensor.cpp	Avoids recreating an existing velocity subscription.
mru_transform/test/test_subscribe_once.cpp	Adds regression coverage for subscribe-once timer behavior.
mru_transform/CMakeLists.txt	Registers and links the new regression test.
.agent/work-plans/issue-23/progress.md	Adds work-plan/progress documentation for issue #23.

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