Parameters#

Autoware ROS nodes have declared parameters which values are provided during the node start up in the form of a parameter file. All the expected parameters with corresponding values should exist in the parameter file. Depending on the application, the parameter values might need to be modified.

Find more information on parameters from the official ROS documentation:

Workflow#

A ROS package which uses the declare_parameter(...) function should:

use the declare_parameter(...), without a default value
create a parameter file
create a schema file

The rationale behind this workflow is to have a verified single source of truth to pass to the ROS node and to be used in the web documentation. The approach reduces the risk of using invalid parameter values and makes maintenance of documentation easier. This is achieved by:

declare_parameter(...) throws an exception if an expected parameter is missing in the parameter file

the schema validates the parameter file in the CI and renders a parameter table, as depicted in the graphics below

flowchart TD
    NodeSchema[Schema file: *.schema.json]
    ParameterFile[Parameter file: *.param.yaml]
    WebDocumentation[Web documentation table]

    NodeSchema -->|Validation| ParameterFile
    NodeSchema -->|Generate| WebDocumentation

Note: a parameter value can still be modified and bypass the validation, as there is no validation during runtime.

Declare Parameter Function#

It is the declare_parameter(...) function which sets the parameter values during a node startup.

declare_parameter<INSERT_TYPE>("INSERT_PARAMETER_1_NAME"),
declare_parameter<INSERT_TYPE>("INSERT_PARAMETER_N_NAME")

As there is no default_value provided, the function throws an exception if a parameter were to be missing in the provided *.param.yaml file. Use a type from the C++ Type column in the table below for the declare_parameter(...) function, replacing INSERT_TYPE.

ParameterType Enum	C++ Type
`PARAMETER_BOOL`	`bool`
`PARAMETER_INTEGER`	`int64_t`
`PARAMETER_DOUBLE`	`double`
`PARAMETER_STRING`	`std::string`
`PARAMETER_BYTE_ARRAY`	`std::vector<uint8_t>`
`PARAMETER_BOOL_ARRAY`	`std::vector<bool>`
`PARAMETER_INTEGER_ARRAY`	`std::vector<int64_t>`
`PARAMETER_DOUBLE_ARRAY`	`std::vector<double>`
`PARAMETER_STRING_ARRAY`	`std::vector<std::string>`

The table has been derived from Parameter Type and Parameter Value.

See example: Lidar Apollo Segmentation TVM Nodes declare function

Parameter File#

The parameter file is minimal as there is no need to provide the user with additional information, e.g., description or type. This is because the associated schema file provides the additional information. Use the template below as a starting point for a ROS node.

/**:
  ros__parameters:
    INSERT_PARAMETER_1_NAME: INSERT_PARAMETER_1_VALUE
    INSERT_PARAMETER_N_NAME: INSERT_PARAMETER_N_VALUE

Note: /** is used instead of the explicit node namespace, this allows the parameter file to be passed to a ROS node which has been remapped.

To adapt the template to the ROS node, replace each INSERT_PARAMETER_..._NAME and INSERT_PARAMETER_..._VALUE for all parameters. Each declare_parameter(...) takes one parameter as input. All the parameter files should have the .param.yaml suffix so that the auto-format can be applied properly.

Autoware has the following two types of parameter files for ROS packages:

Node parameter file
- Node parameter files store the typical parameters provided for each package in Autoware.
  - For example, the parameter of behavior_path_planner
- All nodes in Autoware must have a parameter file if ROS parameters are declared in the node.
- For FOO_package, the parameter is expected to be stored in FOO_package/config.
- The launch file for individual packages must load node parameter by default:

<launch>
  <arg name="foo_node_param_path" default="$(find-pkg-share FOO_package)/config/foo_node.param.yaml" />

  <node pkg="FOO_package" exec="foo_node">
    ...
    <param from="$(var foo_node_param_path)" />
  </node>
</launch>

Launch parameter file
- When a user creates a launch package for the user's vehicle, the user should copy node parameter files for the nodes that are used in the launch file as "launch parameter files".
- Launch parameter files are then customized specifically for the user's vehicle.
  - For example, the customized parameter of behavior_path_planner stored under autoware_launch
- Launch parameter files are stored under the autoware_launch package.

sync-params#

Despite being unused in autoware_launch, node parameter files must be updated after adding or removing parameters in the node implementations. Each node parameter file serves as the master file for the corresponding launch parameter file.

In most cases, updating launch parameter files are automated by sync-params workflow, given that the corresponding node parameter files have been properly updated.

A launch parameter file managed by sync-params workflow has a sync-params comment header starting with # This file is managed by sync-params workflow. By default, a launch parameter file is identical to its corresponding node parameter file, except for the header.

Adding or removing parameters with sync-params workflow#

In general, you should not create a PR for autoware_launch when you simply added or removed some node parameters. In such cases, follow these steps:

Merge the node PR containing the node parameter file update first.
Run sync-params workflow with the desired category. To see the available categories, see the sync-param configuration file.
A PR for the workflow will be created, or the existing PR will be updated if one already exists. The PR is labeled tag:sync-params label.

Overriding parameters with sync-params workflow#

Some of the fields should be different from the corresponding node parameter file. Such fields may be marked with # {OVERRIDE} or # {OVERRIDE: <reason>} comment marker to keep the value different from the upstream node parameter file.

If you naively try to modify the parameter in the launch parameter file as in the next example, the next sync-params workflow run will try to revert the parameter to foo: 42, matching to the node parameter file.

 # NG
-foo: 42
+foo: 40

To make the change persist, open a PR that updates the launch parameter file as following:

 # OK
-foo: 42
+foo: 40 # {OVERRIDE}

If there is already a comment on the line, place the marker before the existing comment:

 # OK
-bar: [1, 2, 3, 4] # existing comment
+bar: [5, 6, 7, 8] # {OVERRIDE} existing comment

Tip: make the node parameter file as identical as possible to the intended launch parameter file, so that the override can be minimized.

Updating sync-params configurations#

To add a new pair of a node parameter file and a launch parameter file, update the sync-param configuration file, following the next example.

perception: # category
  - repository: autowarefoundation/autoware_universe # the source repository
    ref: main
    files:
      - # node parameter file path in the source repository
        source: perception/autoware_image_object_locator/config/bbox_object_locator.param.yaml
        # List of launch parameter file paths in autoware_launch repository
        variants:
          - path: autoware_launch/config/perception/object_recognition/detection/camera_vru_detection/near_range_camera_vru_detector.param.yaml

And then run python .github/scripts/sync_params.py perception (replace perception with your category) locally, which is the script that sync-params workflow uses under the hood. Files in the same category might be updated as well, but commit only the file that you have just added and discard anything else. Other files should be addressed with the autogenerated sync-params PR.

To remove a pair, simply remove the launch parameter file entry from the sync-param config file, and remove the sync-params comment header.

To specify the new upstream, in cases such as when the node package has been moved to a different repository, remove the old pair, and then re-add the launch parameter file with the new upstream.

JSON Schema#

JSON Schema is used the validate the parameter file(s) ensuring that it has the correct structure and content. Using JSON Schema for this purpose is considered best practice for cloud-native development. The schema template below shall be used as a starting point when defining the schema for a ROS node.

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "title": "INSERT_TITLE",
  "type": "object",
  "definitions": {
    "INSERT_ROS_NODE_NAME": {
      "type": "object",
      "properties": {
        "INSERT_PARAMETER_1_NAME": {
          "type": "INSERT_TYPE",
          "description": "INSERT_DESCRIPTION",
          "default": "INSERT_DEFAULT",
          "INSERT_BOUND_CONDITION(S)": INSERT_BOUND_VALUE(S)
        },
        "INSERT_PARAMETER_N_NAME": {
          "type": "INSERT_TYPE",
          "description": "INSERT_DESCRIPTION",
          "default": "INSERT_DEFAULT",
          "INSERT_BOUND_CONDITION(S)": INSERT_BOUND_VALUE(S)
        }
      },
      "required": ["INSERT_PARAMETER_1_NAME", "INSERT_PARAMETER_N_NAME"],
      "additionalProperties": false
    }
  },
  "properties": {
    "/**": {
      "type": "object",
      "properties": {
        "ros__parameters": {
          "$ref": "#/definitions/INSERT_ROS_NODE_NAME"
        }
      },
      "required": ["ros__parameters"],
      "additionalProperties": false
    }
  },
  "required": ["/**"],
  "additionalProperties": false
}

The schema file path is INSERT_PATH_TO_PACKAGE/schema/ and the schema file name is INSERT_NODE_NAME.schema.json. To adapt the template to the ROS node, replace each INSERT_... and add all parameters 1..N.

See example: Image Projection Based Fusion - Pointpainting schema

Attributes#

Parameters have several attributes, some are required and some optional. The optional attributes are highly encouraged when applicable, as they provide useful information about a parameter and can ensure the value of the parameter is within its bounds.

Required#

name
type
- see JSON Schema types
description

Optional#

default
- a tested and verified value, see JSON Schema default
bound(s)
- type dependent, e.g., integer, range and size

Tips and Tricks#

Using well established standards enables the use of conventional tooling. Below is an example of how to link a schema to the parameter file(s) using VS Code. This enables a developer with convenient features such as auto-complete and parameter bound validation.

In the root directory of where the project is hosted, create a .vscode folder with two files; extensions.json containing

{
  "recommendations": ["redhat.vscode-yaml"]
}

and settings.json containing

{
  "yaml.schemas": {
    "./INSERT_PATH_TO_PACKAGE/schema/INSERT_NODE_NAME.schema.json": "**/INSERT_NODE_NAME/config/*.param.yaml"
  }
}

The RedHat YAML extension enables validation of YAML files using JSON Schema and the "yaml.schemas" setting associates the *.schema.json file with all *.param.yaml files in the config/ folder.