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ROS 2 Overview Introduction ROS 2 Overview Introduction
This is meant to explain ROS 2 basics, design, distribution and features just in overview.ROS 2 documentation if we need to know more details.
ROS 2 Overview Introduction Agenda
Governance
Distributions
Architecture / Design
Basic Concepts
Samples / Demos
Remarkable Features
3rd Party Packages
ROS 2 Overview Introduction Governance
is a new initiative of the OSRF to organize and strengthen project governance and community involvement. The OSRA is a mixed membership and meritocratic model, following other successful foundations for open-source projects.
ROS 2 Overview Introduction The ROS Project Management Committee is responsible for the day-to-day operations of the ROS 2 project. The ROS PMC consists of the Project Leader, the ROS PMC Members (who have full voting rights)
See Current ROS PMC Constituents .
ROS 2 Overview Introduction
ROS 2 Overview Introduction
Distribution Name
Release Date
End Of Life Date
Kilted Kaiju
May 2025
N.A
Jazzy Jalisco
May 23rd, 2024
May 2029
Iron Irwini
May 23rd, 2023
November 2024
Humble Hawksbill
May 23rd, 2022
May 2027
ROS 2 Overview Introduction
ROS 2 Overview Introduction
C++14 / C++17 Standard
Python version 3.6 or later
colcon to meta-build system
colcon handles ament(ROS 2) and catkin(ROS 1)
.msg, .srv and .action files
Basically compatible, but might need to be updated
OMG IDL 4.2 SupportSerializer is ROS 2 MiddleWare's responsibility
Steady, System and ROS clock available
ROS 2 Overview Introduction
ROS 2 Overview Introduction
ROS 2 Overview Introduction Data Distribution Service
The OMG Data-Distribution Service for Real-Time Systems® (DDS®) is the first open international middleware standard directly addressing publish-subscribe communications for real-time and embedded systems.
DDS introduces a virtual Global Data Space where applications can share information by simply reading and writing data-objects addressed by means of an application-defined name (Topic) and a key. DDS features fine and extensive control of QoS parameters, including reliability, bandwidth, delivery deadlines, and resource limits. DDS also supports the construction of local object models on top of the Global Data Space.
ROS 2 Overview Introduction Basic Concepts
ROS 2 Overview Introduction
A node can be a component
Single process can be constructed with multi-components
Component can be loaded during runtime via component container
Intra-Process Manager
ROS 2 Overview Introduction A managed life cycle for nodes allows greater control over the state of ROS system. It allows roslaunch to ensure that all components have been instantiated correctly before it allows any component to begin executing its behavior. It will also allow nodes to be restarted or replaced on-line.
Primary State
Unconfigure, Inactive, Active and Finalized
Transition State
Configuring, ClearningUp, ShuttingDown, Activating, Deactivating and ErrorProcessing
ROS 2 Overview Introduction
ROS 2 Overview Introduction
Just like ROS 1 Nodelet
Multiple nodes in a single process
Can load and unload the composable node
Composable nodes as shared libraries
ROS 2 Overview Introduction ROS 2 provides executor class aside from Node class, which can be used to dispatch the task to execute the event such as subscription, timer, service and any waitable so on. application has flexibility to use executor as it likes.
SingleThreadedExecutor: single thread to dispatch task and execute.
MultiThreadedExecutor: mulith-thread to dispatch task and execute. (via std::thread::hardware_concurrency)
StaticSingleThreadedExecutor (deprecated): statically collect entities for task. that said once spins, it will not collect or update any entities.EventExecutor: Uses events queue in the Executor to execute the entities from associated nodes.
ROS 2 Overview Introduction
ROS 2 Overview Introduction
ROS 2 Overview Introduction
ROS 2 Overview Introduction
No parameter server
Parameters are hosted in Node
Async / Sync Parameter Client
get, set, list, delete and describe methodsuser callback to validate parameter change
ROS 2 Overview Introduction Parameter Events
ROS 2 Overview Introduction
ROS 2 Overview Introduction
ROS 2 Overview Introduction
ROS 2 Overview Introduction
logging subsystem can output the log to console, files and /rosout topic.
/rosout topic is to publish and subscribe all logging data in ROS 2 system.Multiple severity levels are supported.
Environmental variables to support log configuration and format.
ROS 2 Overview Introduction
Similar with ROS 1 roslaunch.
The launch system in ROS 2 is meant to automate the running of many nodes with a single command.
ROS 2 launch files can be written in Python, XML, or YAML.
Parameters, remapping rules arguments and process related events are supported.
see more details for https://design.ros2.org/articles/roslaunch.html .
ROS 2 Overview Introduction
ros2 bag is a command line tool for recording data published on topics and services in your ROS 2 system.backend data base can be configured either MCAP (default from Iron) or SQLite3 (default until humble)
Not only for topics, but services can be also recorded and playback.
ROS 2 Overview Introduction
ROS 2 Overview Introduction
ROS 2 Overview Introduction
QoS policies such as history, depth, reliability, durability, deadline so on.
QoS preset profiles, e.g) system_default, sensor_data and service.
QoS events, callback to be fired based on the event, i.e) deadline missed, liveliness missed.
QoS incompatibility can happen between publisher and subscriber.
MachedEvent can be generated when any publisher and subscription establishes or drops the connection between them.
ROS 2 Overview Introduction ROS_DOMAIN_ID Partition
ROS_DOMAIN_ID , primary mechanism for having different logical networks share a physical network is known as the Domain ID.
Discovery protocol initiated in the same subnet By default.
User can configure the discovery range with environmental variable, such as only localhost, specific peers.
ROS 2 Overview Introduction The ability to secure communications among nodes within the ROS 2 computational graph.
see Setting up security for more details.
ROS 2 Overview Introduction
True Zero Copy / Write Just Once
No encapsulation / No Serialization
Copy-Less communication channel using shared memory.
Application borrows memory from RMW Implementation.
Fast-DDS v2.2.0 (ros:galactic or later)
ROS 2 Overview Introduction
LoanedMessage
Constraints
bound data type only supported. (plain data type)
Configuration
Suitable for PREALLOCATED_MEMORY_MODE and PREALLOCATED_WITH_REALLOC_MEMORY_MODE memory configurations only
see MemoryManagementPolicy
ROS 2 Overview Introduction
DDS
Tier
Description
Fast-DDS
1
Zero Copy supported. Even with shared memory transport, DDS feature full supported.
Cyclonedds
1
DDS with shared memory bypass by iceoryx which requires daemon. When using shared memory, DDS feature cannot be supported such as QoS.
RTI Connext DDS
1
Commercial only, but most featured DDS implementation
Eclipse Iceoryx
2
Only shared memory w/o network, daemon process required.
ROS 2 Overview Introduction
ROS 2 Overview Introduction Sync / Async Publication
in general with ROS 2, we recommend async send not to block the application threads, so that application can be available for tasks in application perspective. on the other hand, async causes context switches, this could affect the latency.
eProsima Fast-DDS can be configured (default async)
Eclipse Cyclonedds only supports sync send.
ROS 2 Overview Introduction Wait for Acknowledgements
This operation blocks the calling thread until either all data written by the reliable DataWriter entities is acknowledged by all matched reliable DataReader entities, or else the duration specified by the max_wait parameter elapses, whichever happens first. A return value of OK indicates that all the samples written have been acknowledged by all reliable matched data readers; a return value of TIMEOUT indicates that max_wait elapsed before all the data was acknowledged.
ROS 2 Overview Introduction
ROS 2 Overview Introduction
ROS 2 Overview Introduction ContentFilteredTopic provides the improvement for CPU consumption and network traffic.
Reader can get what they need to receive.
Much less network consumption and user callbacks.
Application can be agnostic from filtering.
Filtering expression and parameter is really flexible.
Filtering can be reconfigured at runtime.
ROS 2 Overview Introduction
Differentiated Services is a widely-used QoS architecture for IP networks. The required DS-based QoS is set by the application in the 6-bit DS Code Point (DSCP) sub-field of the 8-bit DS field in the IP packet header.
5G network 5QI: The Network Exposure Function (NEF) in the 5G core network provides robust and secure API for QoS specification. This API enables applications to programmatically (HTTP-JSON) specify required QoS by associating 5G QoS Identifiers (5QIs) to flow identifers, as shown in the figure next.
ROS 2 Overview Introduction
ROS 2 Overview Introduction puts ROS 2 onto microcontrollers!
ROS 2 Overview Introduction
ROS 2 Overview Introduction
ROS 2 Overview Introduction This feature depends on Service introspection implemented in Iron. rosbag2 takes advantage of it to record all service requests and responses, and also replays service data from the bag file.
This feature allows you to debug/enhance/test/simulate the ROS 2 services more efficiently.
ROS 2 Overview Introduction
ROS 2 Overview Introduction System Packages
ROS 2 Overview Introduction The Discovery Server provides a Client-Server Architecture that allows nodes to connect with each other using an intermediate server. Each node functions as a discovery client, sharing its info with one or more discovery servers and receiving discovery information from it. This reduces discovery-related network traffic and it does not require multicasting capabilities.
ROS 2 Overview Introduction A new ROS MiddleWare (RMW) that integrates Zenoh with ROS 2 and rmw_zenoh is now available. However, it is still a preview because there are some known bugs in it, and we aren’t quite ready to commit to it for the long term.
rmw_zenoh is one of Non-DDS RMW implementations.
Note that rmw_zenoh requires Zenoh Router daemon running.
To use, we need to compile rmw_zenoh from the source .
ROS 2 Overview Introduction #
#
By default, discovery traffic is only in local host system. If network communication is needed, we need to configure zenoh router and restart .
uses CDR as the serialization format. (Compatible with DDS based RMWs)
ROS 2 Overview Introduction ROS 2 Persistent Parameter Server, that resides in the ROS 2 system to serve the parameter daemon. The other nodes(e.g the client demo provided in the code) can write/read the parameter in Parameter Server, and Parameter Server is able to store the parameter into the persistent storage which user can specify such as tmpfs, nfs, or disk .
see more details for https://github.com/fujitatomoya/ros2_persist_parameter_server
ROS 2 Overview Introduction
ROS 2 Overview Introduction
ROS 2 Overview Introduction ros2ai is a next-generation ROS 2 command line interface extension with OpenAI and Ollama .
ROS 2 Overview Introduction See how it works
ROS 2 Overview Introduction
ROS 2 service load-balancing in application layer without protocol change.
Support multiple service servers on the same service path to have robustness and load-balancing mechanism.
Scale / Offload ROS 2 service server/client application with remapping but code modification.
ROS 2 Overview Introduction
ROS 2 Overview Introduction Reference
### Topic
ros2 run demo_nodes_cpp talker
ros2 run demo_nodes_cpp listener
ros2 topic list
ros2 topic info /chatter
ros2 note list
### Service
ros2 run demo_nodes_cpp add_two_ints_server
ros2 service list
ros2 run demo_nodes_cpp add_two_ints_client
### Parameter
ros2 run demo_nodes_cpp parameter_blackboard
ros2 param set /parameter_blackboard greeting hello
ros2 param list
ros2 param get /parameter_blackboard greeting
### Action
ros2 run action_tutorials_cpp fibonacci_action_server
ros2 action list
ros2 action info /fibonacci
ros2 run action_tutorials_cpp fibonacci_action_client
# Lifecycle
ros2 run lifecycle lifecycle_talker
ros2 run lifecycle lifecycle_listener
ros2 run lifecycle lifecycle_service_client
ros2 lifecycle nodes
ros2 lifecycle get /lc_talker
# Composition
ros2 component types
ros2 run rclcpp_components component_container
ros2 component list
ros2 component load /ComponentManager composition composition::Talker
ros2 component load /ComponentManager composition composition::Listener
ros2 component list
# Final True Zero Copy Data Sharing
# https://fast-dds.docs.eprosima.com/en/latest/fastdds/use_cases/zero_copy/zero_copy.html
# https://discourse.ros.org/t/fast-dds-v2-2-0-latency-performance/18989
# Intra-Process Communication Performance Improvement by eProsima
# details can be found on https://discourse.ros.org/t/rmw-proposal-content-filtered-topic-suport/16113/6
# Ericsson AB : https://github.com/ros2/design/pull/304
# Network Identifier can be gotten from RMW interface,
# then user can control network via iptables or so on.
Original Issue: https://github.com/ros2/rosbag2/issues/773
NOTE: add one more dash "->", this is to avoid html comment directive.
```mermaid
graph LR
A[Service Client A] <-> D((Request/Response))
B[Service Client B] <-> D((Request/Response))
C[Service Client C] <-> D((Request/Response))
D((Request/Response)) <-> E[Service Server]
```
```mermaid
graph LR
A[Service Client A] <-> D((Request/Response))
B[Service Client B] <-> D((Request/Response))
C[Service Client C] <-> D((Request/Response))
D((Request/Response)) <-> E[Service Server]
D((Request/Response)) -- /service_events -> F{Service Introspection}
F{Service Introspection} -- recording -> G[rosbag2 service]
G[rosbag2 service] -- replaying -> D((Request/Response))
```
Design: https://github.com/ros2/rmw_zenoh/blob/rolling/docs/design.md