CallbackIsolatedExecutor

CallbackIsolatedExecutor is a ROS 2 executor — and a matching component container — that assigns a dedicated OS thread to each CallbackGroup, enabling per-callback scheduling control (policy, priority, and CPU affinity) handled entirely by the Linux kernel.

It is a standalone rclcpp-based package: it requires no changes to rcl or rclcpp and can be installed and used on its own.

Why

Standard ROS 2 executors share a pool of threads across callbacks — you cannot control which callback runs on which CPU or at what priority.

Standard Executor:                  CallbackIsolatedExecutor:

  CallbackGroup A ─┐                 CallbackGroup A → Thread (FIFO, prio=90, CPU0)
  CallbackGroup B ─┼→ Thread Pool    CallbackGroup B → Thread (FIFO, prio=80, CPU1)
  CallbackGroup C ─┘                 CallbackGroup C → Thread (CFS,  nice=0)

  No per-callback control            Full OS-level scheduling control

With CallbackIsolatedExecutor, each CallbackGroup maps to exactly one OS thread. Scheduling is then delegated to the Linux kernel: you assign SCHED_FIFO, SCHED_RR, SCHED_DEADLINE, or CFS (SCHED_OTHER / SCHED_BATCH) parameters per CallbackGroup through a single YAML file, applied by the cie_thread_configurator.

For the design rationale and evaluation, see the RTAS 2025 paper Middleware-Transparent Callback Enforcement in Commoditized Component-Oriented Real-Time Systems.

This package continues the development of sykwer/callback_isolated_executor, the original implementation accompanying that paper.

Supported Environments

Category	Supported Versions / Notes
ROS 2	Humble (only with the rclcpp client library)
Linux Distribution	Ubuntu 22.04 (Jammy Jellyfish)

This reflects the current status; support is expected to expand in the future.

Pages

• Integration Guide — Build, install, switch the executor, and set up the thread configurator
• YAML Specification — Complete reference for the thread configuration file
• Non-ROS Threads — Managing scheduling for threads outside the ROS 2 executor
• Tutorial — End-to-end walkthrough with the sample application
• Comparison with Other Executors — Real-time properties versus other ROS 2 executors

Relation to Agnocast

Agnocast provides an Agnocast-compatible port of this executor (agnocast::CallbackIsolatedAgnocastExecutor) that additionally schedules Agnocast's zero-copy callbacks. If you use Agnocast, refer to the CallbackIsolatedExecutor section of the Agnocast documentation. This site documents the original, rclcpp-only CallbackIsolatedExecutor.

Citation

If you find CallbackIsolatedExecutor useful in your research, please consider citing:

T. Ishikawa-Aso, A. Yano, T. Azumi, and S. Kato, "Work in Progress: Middleware-Transparent Callback Enforcement in Commoditized Component-Oriented Real-Time Systems," in Proc. of 31st IEEE Real-Time and Embedded Technology and Applications Symposium (RTAS), 2025, pp. 426–429.

BibTeX

@inproceedings{ishikawa2025work,
  title={Work in Progress: Middleware-Transparent Callback Enforcement in Commoditized Component-Oriented Real-Time Systems},
  author={Ishikawa-Aso, Takahiro and Yano, Atsushi and Azumi, Takuya and Kato, Shinpei},
  booktitle={Proc. of 31st IEEE Real-Time and Embedded Technology and Applications Symposium (RTAS)},
  pages={426--429},
  year={2025},
  organization={IEEE}
}