Skip to content

Mention rmw_specific_{pub,sub}_payload in rmw impl tutorial (backport #5967) #5969

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Oct 20, 2025
Merged

Mention rmw_specific_{pub,sub}_payload in rmw impl tutorial (backport #5967) #5969

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
7 changes: 5 additions & 2 deletions source/Tutorials/Advanced/Creating-An-RMW-Implementation.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -455,8 +455,11 @@ These tests can use ``rmw``'s ``rmw_get_implementation_identifier()`` `function
Middleware- and ``rmw`` implementation-specific configuration
-------------------------------------------------------------

The ``rmw`` interface as defined by that package does not support passing arbitrary configuration data to the implementation or the underlying middleware.
To get around that and introduce some flexibility, some implementations use environment variables: ``RMW_FASTRTPS_*``, ``RMW_CONNEXT_*``, etc.
The ``rmw`` interface allows providing arbitrary implementation-specific configuration payloads for publishers and subscriptions through the type-erased ``rmw_specific_publisher_payload`` / ``rmw_specific_subscription_payload`` fields in ``rmw_publisher_options_t`` / ``rmw_subscription_options_t``.
This is set by users through ``RMWImplementationSpecificPublisherPayload`` / ``RMWImplementationSpecificSubscriptionPayload`` in ``rclcpp``, for example.
This is an advanced, non-portable feature that is not currently used by any (tier 1) implementations.

For a bit more flexibility, some implementations use environment variables: ``RMW_FASTRTPS_*``, ``RMW_CONNEXT_*``, etc.
The underlying middleware may also be configurable through environment variables: ``FASTDDS_*``, ``ZENOH_*``, ``CYCLONEDDS_*``, ``EMAIL_*``, etc.
For example, the ``CYCLONEDDS_URI``, ``FASTDDS_DEFAULT_PROFILES_FILE``, and ``ZENOH_SESSION_CONFIG_URI`` environment variables can be used to provide a path to a full configuration file if the relevant middleware is used.

Expand Down