You're reading the documentation for an older, but still supported, version of ROS 2. For information on the latest version, please have a look at Galactic.

ROS 2 Humble Hawksbill (codename ‘humble’; May, 2022)

Table of Contents

Supported Platforms
Installation
New features in this ROS 2 release
- ros_args attribute & ros_arguments parameter for nodes in launch files
- SROS2 Security enclaves now support Certificate Revocation Lists
Changes since the Galactic release
- common_interfaces
- rmw
- rcl
- rclcpp
- ros2cli
- robot_state_publisher
- rosidl_cmake
- geometry2
Known Issues
Release Timeline

Humble Hawksbill is the eighth release of ROS 2. What follows is highlights of the important changes and features in Humble Hawksbill since the last release.

Supported Platforms 

Humble Hawksbill is primarily supported on the following platforms:

Tier 1 platforms:

TBD

Tier 2 platforms:

TBD

Tier 3 platforms:

TBD

For more information about RMW implementations, compiler / interpreter versions, and system dependency versions see REP 2000.

New features in this ROS 2 release 

`ros_args` attribute & `ros_arguments` parameter for nodes in launch files 

It is now possible to provide ROS-specific node arguments directly, without needing to use args with a leading --ros-args flag:

<launch>
  <node pkg="demo_nodes_cpp" exec="talker" ros_args="--log-level debug" />
</launch>

launch:
- node:
    pkg: demo_nodes_cpp
    exec: talker
    ros_args: '--log-level debug'

The corresponding parameter for the Node action in Python launch files is ros_arguments:

from launch import LaunchDescription
import launch_ros.actions

def generate_launch_description():
    return LaunchDescription([
        launch_ros.actions.Node(
            package='demo_nodes_cpp',
            executable='talker',
            ros_arguments=['--log-level', 'debug'],
        ),
    ])

Related PRs: ros2/launch_ros#249 and ros2/launch_ros#253.

SROS2 Security enclaves now support Certificate Revocation Lists 

Certificate Revocation Lists (CRLs) are a concept where particular certificates can be revoked before their expiration. As of Humble, it is now possible to put a CRL in an SROS2 security enclave and have it be honored. See the SROS2 tutorials for an example of how to use it.

Changes since the Galactic release 

common_interfaces 

Support Textures and Embedded Meshes for Marker Messages

These two additions will improve the ability to both visualize data in new ways with standard messages and, simultaneously, enable the ability to track this data in rosbag.

Textures bring the addition of three new fields to markers:

# Texture resource is a special URI that can either reference a texture file in
# a format acceptable to (resource retriever)[https://index.ros.org/p/resource_retriever/]
# or an embedded texture via a string matching the format:
#   "embedded://texture_name"
string texture_resource
# An image to be loaded into the rendering engine as the texture for this marker.
# This will be used iff texture_resource is set to embedded.
sensor_msgs/CompressedImage texture
# Location of each vertex within the texture; in the range: [0.0-1.0]
UVCoordinate[] uv_coordinates

RViz will fully support texture rendering through the embedded format.

To those familiar with mesh_resource, resource_retriever should be familiar. This will allow the programmer to choose where they want to load data from, either a local file or a networked file. In the interest of being able to record all data in a rosbag, the ability to embed the texture image is included.

Meshes were modified in a similar way to add the ability to embed a raw Mesh file for the purpose of recording and are modified in a similar way. The Meshfile message has two fields:

# The filename is used for both debug purposes and to provide a file extension
# for whatever parser is used.
string filename

# This stores the raw text of the mesh file.
uint8[] data

The embedded Meshfile message is not yet supported in implementation.

rmw 

`struct` type name suffix changed from `_t` to `_s`

To avoid type name duplication errors between struct type names and their typedef-ed aliases when generating code documentation, the suffix for all struct type names has been changed from _t to _s. Aliases with _t suffixes remain in place. Thus, this change is a breaking change only for code that uses full struct type specifiers i.e. struct type_name_t.

See ros2/rmw#313 for more details.

rcl 

`struct` type name suffix changed from `_t` to `_s`

To avoid type name duplication errors between struct type names and their typedef-ed aliases when generating code documentation, the suffix for all struct type names has been changed from _t to _s. Aliases with _t suffixes remain in place. Thus, this change is a breaking change only for code that uses full struct type specifiers i.e. struct type_name_t.

See ros2/rcl#932 for more details.

rclcpp 

Support Type Adaption for Publishers and Subscriptions

After defining a type adapter, custom data structures can be used directly by publishers and subscribers, which helps to avoid additional work for the programmer and potential sources of errors. This is especially useful when working with complex data types, such as when converting OpenCV’s cv::Mat to ROS’s sensor_msgs/msg/Image type.

Here is an example of a type adapter that converts std_msgs::msg::String to std::string:

template<>
struct rclcpp::TypeAdapter<
   std::string,
   std_msgs::msg::String
>
{
  using is_specialized = std::true_type;
  using custom_type = std::string;
  using ros_message_type = std_msgs::msg::String;

  static
  void
  convert_to_ros_message(
    const custom_type & source,
    ros_message_type & destination)
  {
    destination.data = source;
  }

  static
  void
  convert_to_custom(
    const ros_message_type & source,
    custom_type & destination)
  {
    destination = source.data;
  }
};

And an example of how the type adapter can be used:

using MyAdaptedType = TypeAdapter<std::string, std_msgs::msg::String>;

// Publish a std::string
auto pub = node->create_publisher<MyAdaptedType>(...);
std::string custom_msg = "My std::string"
pub->publish(custom_msg);

// Pass a std::string to a subscription's callback
auto sub = node->create_subscription<MyAdaptedType>(
  "topic",
  10,
  [](const std::string & msg) {...});

To learn more, see the publisher and subscription) examples, as well as a more complex demo. For more details, see REP 2007.

`get_callback_groups` method removed from `NodeBase` and `Node` classes

for_each_callback_group() method has replaced get_callback_groups() by providing a thread-safe way to access callback_groups_ vector. for_each_callback_group() accepts a function as an argument, iterates over the stored callback groups, and calls the passed function to ones that are valid.

For more details, please refer to this pull request.

`add_to_wait_set` method from `Waitable` class changes its return type from `bool` to `void`

Before, classes derived from Waitable overriding add_to_wait_set were returning false when failing to add elements to the wait set, so the caller had to check this return value and throw or handle the error. This error handling should now be done directly on add_to_wait_set method, throwing if necessary. It is not required to return anything if no errors happened. Thus, this is a breaking change for downstream uses of Waitable.

See ros2/rclcpp#1612 for more details.

`get_notify_guard_condition` method return type from `NodeBaseInterface` class changed

Now rclcpp uses the GuardCondition class wrapper around rcl_guard_condition_t, so get_notify_guard_condition returns a reference to the node’s rclcpp::GuardCondition. Thus, this is a breaking change for downstream uses of NodeBaseInterface and NodeBase.

See ros2/rclcpp#1612 for more details.

ros2cli 

`ros2 topic pub` will wait for one matching subscription when using `--times/--once/-1`

When using --times/--once/-1 flags, ros2 topic pub will wait for one matching subscription to be found before starting to publish. This avoids the issue of the ros2cli node starting to publish before discovering a matching subscription, which results in some of the first messages being lost. This is particularly unexpected when using a reliable qos profile.

The number of matching subscriptions to wait before starting publishing can be configured with the -w/--wait-matching-subscriptions flags, e.g.:

ros2 topic pub -1 -w 3 /chatter std_msgs/msg/String "{data: 'foo'}"

to wait for three matching subscriptions before starting to publish.

-w can also be used independently of --times/--once/-1 but it only defaults to one when combined with them, otherwise the -w default is zero.

See https://github.com/ros2/ros2cli/pull/642 for more details.

`ros2 param dump` default output changed

--print option for dump command was deprecated.

It prints to stdout by default:
ros2 param dump /my_node_name
--output-dir option for dump command was deprecated.

To dump parameters to a file, run:
ros2 param dump /my_node_name > my_node_name.yaml

robot_state_publisher 

Removal of deprecated `use_tf_static` parameter

The deprecated use_tf_static parameter has been removed from robot_state_publisher. This means that static transforms are unconditionally published to the /tf_static topic, and that the static transforms are published in a transient_local Quality of Service. This was the default behavior, and the behavior which the tf2_ros::TransformListener class expected before, so most code will not have to be changed. Any code that was relying on robot_state_publisher to periodically publish static transforms to /tf will have to be updated to subscribe to /tf_static as a transient_local subscription instead.

rosidl_cmake 

Deprecation of `rosidl_target_interfaces()`

The CMake function rosidl_target_interfaces() has been deprecated, and now issues a CMake warning when called. Users wanting to use messages/services/actions in the same ROS package that generated them should instead call rosidl_get_typesupport_target() and then target_link_libraries() to make their targets depend on the returned typesupport target. See https://github.com/ros2/rosidl/pull/606 for more details, and https://github.com/ros2/demos/pull/529 for an example of using the new function.

geometry2 

Deprecation of TF2Error::NO_ERROR, etc

The tf2 library uses an enumeration called TF2Error to return errors. Unfortunately, one of the enumerators in there is called NO_ERROR, which conflicts with a macro on Windows. To remedy this, a new set of enumerators in TF2Error were created, each with a TF2 prefix. The previous enumerators are still available, but are now deprecated and will print a deprecation warning if used. All code that uses the TF2Error enumerator should be updated to use the new TF2 prefixed errors. See https://github.com/ros2/geometry2/pull/349 for more details.

More intuitive command-line arguments for static_transform_publisher

The static_transform_publisher program used to take arguments like: ros2 run tf2_ros static_transform_publisher 0 0 0 0 0 0 1 foo bar. The first three numbers are the translation x, y, and z, the next 4 are the quaternion x, y, z, and w, and the last two arguments are the parent and child frame IDs. While this worked, it had a couple of problems:

The user had to specify all of the arguments, even if only setting one number
Reading the command-line to figure out what it was publishing was tricky

To fix both of these issues, the command-line handling has been changed to use flags instead, and all flags except for --frame-id and --child-frame-id are optional. Thus, the above command-line can be simplified to: ros2 run tf2_ros static_transform_publisher --frame-id foo --child-frame-id bar To change just the translation x, the command-line would be: ros2 run tf2_ros static_transform_publisher --x 1.5 --frame-id foo --child-frame-id bar.

The old-style arguments are still allowed in this release, but are deprecated and will print a warning. They will be removed in future releases. See https://github.com/ros2/geometry2/pull/392 for more details.

Transform listener spin thread no longer executes node callbacks

tf2_ros::TransformListener no longer spins on the provided node object. Instead, it creates a callback group to execute callbacks on the entities it creates internally. This means if you have set the parameter spin_thread=true when creating a transform listener, you can no longer depend on your own callbacks to be executed. You must call a spin function on your node (e.g. rclcpp::spin), or add your node to your own executor.

Related pull request: geometry2#442

Known Issues 

To come.

Release Timeline 

Mon. March 21, 2022 - Alpha + RMW freeze
Preliminary testing and stabilization of ROS Base 1 packages, and API and feature freeze for RMW provider packages.

Mon. April 4, 2022 - Freeze
API and feature freeze for ROS Base 1 packages in Rolling Ridley. Only bug fix releases should be made after this point. New packages can be released independently.

Mon. April 18, 2022 - Branch
Branch from Rolling Ridley. rosdistro is reopened for Rolling PRs for ROS Base 1 packages. Humble development shifts from ros-rolling-* packages to ros-humble-* packages.

Mon. April 25, 2022 - Beta
Updated releases of ROS Desktop 2 packages available. Call for general testing.

Mon. May 16, 2022 - Release Candidate
Release Candidate packages are built. Updated releases of ROS Desktop 2 packages available.

Thu. May 19, 2022 - Distro Freeze
Freeze rosdistro. No PRs for Humble on the rosdistro repo will be merged (reopens after the release announcement).

Mon. May 23, 2022 - General Availability
Release announcement. rosdistro is reopened for Humble PRs.

1(1,2,3): The ros_base variant is described in REP 2001 (ros-base).
2(1,2): The desktop variant is described in REP 2001 (desktop-variants).

ROS 2 Humble Hawksbill (codename ‘humble’; May, 2022)

Support Textures and Embedded Meshes for Marker Messages

struct type name suffix changed from _t to _s

struct type name suffix changed from _t to _s

Support Type Adaption for Publishers and Subscriptions

get_callback_groups method removed from NodeBase and Node classes

add_to_wait_set method from Waitable class changes its return type from bool to void

get_notify_guard_condition method return type from NodeBaseInterface class changed

ros2 topic pub will wait for one matching subscription when using --times/--once/-1

ros2 param dump default output changed

Removal of deprecated use_tf_static parameter

Deprecation of rosidl_target_interfaces()

Deprecation of TF2Error::NO_ERROR, etc

More intuitive command-line arguments for static_transform_publisher

Transform listener spin thread no longer executes node callbacks

`struct` type name suffix changed from `_t` to `_s`

`struct` type name suffix changed from `_t` to `_s`

`get_callback_groups` method removed from `NodeBase` and `Node` classes

`add_to_wait_set` method from `Waitable` class changes its return type from `bool` to `void`

`get_notify_guard_condition` method return type from `NodeBaseInterface` class changed

`ros2 topic pub` will wait for one matching subscription when using `--times/--once/-1`

`ros2 param dump` default output changed

Removal of deprecated `use_tf_static` parameter

Deprecation of `rosidl_target_interfaces()`