getParam (and getParams) not returning anything

[guru-florida]

Using Ros2 Web Bridge on ROS2 Eloquent:

I am calling getParam with a valid node name but not getting param data back. The callback is not executed. I do get plenty of subscription callbacks so the websocket and communication to ros2 web bridge is working fine. Inspecting the network tab details, I see that the request is properly going out but the web bridge is replying back with a non-descript error. You can see in this screenshot a bunch of /compliance/params subscription events (great!) but the service call to rosapi/get_param is failing with set_level "error":

I enabled debug stats in the ros2 bridge using:
DEBUG=ros2-web-bridge:Bridge node bin/rosbridge.js
...and I get this related error:

ros2-web-bridge:Bridge JSON command received: {"op":"call_service","id":"call_service:/rosapi/get_param:44","service":"/rosapi/get_param","type":"rosapi/GetParam","args":{"name":"/imu"}} +71ms
  ros2-web-bridge:Bridge Exception caught in Bridge.executeCommand(): Error: The message required does not exist: rosapi, srv, GetParam +1ms
  ros2-web-bridge:Bridge Error: Error: The message required does not exist: rosapi, srv, GetParam happened when executing command call_service +0ms
  ros2-web-bridge:Bridge Response: {"op":"set_level","id":"call_service:/rosapi/get_param:44","level":"error"} +0ms

It suggests the rosapi.srv.GetParam message doesnt exist. I took a gander around the rclnodejs generated directory and I indeed can't find the message. Seems like the relevant service messages would be in generated/rcl_interfaces, yes? I see in that folder a bunch of param server and request/result messages. Grep'ing for msgname within all those generated files I get:

$ find node_modules/rclnodejs/generated/rcl_interfaces -exec  grep "msgName\": " {} \;
  "msgName": "SetParametersAtomically_Request"
  "msgName": "GetParameterTypes_Response"
  "msgName": "ParameterValue"
  "msgName": "GetParameters_Response"
  "msgName": "GetParameters_Request"
  "msgName": "ListParametersResult"
  "msgName": "Log"
  "msgName": "ParameterEventDescriptors"
  "msgName": "FloatingPointRange"
  "msgName": "SetParametersResult"
  "msgName": "IntegerRange"
  "msgName": "ListParameters_Response"
  "msgName": "ParameterType"
  "msgName": "ListParameters_Request"
  "msgName": "GetParameterTypes_Request"
  "msgName": "SetParametersAtomically_Response"
  "msgName": "Parameter"
  "msgName": "IntraProcessMessage"
  "msgName": "SetParameters_Response"
  "msgName": "SetParameters_Request"
  "msgName": "ParameterEvent"
  "msgName": "DescribeParameters_Request"
  "msgName": "DescribeParameters_Response"
  "msgName": "ParameterDescriptor"

Did Eloquent perhaps change the Param service messages? Any other advice/suggestions?

Thank you,
Colin

[minggangw]

Thanks for reporting this problem. The rosapi is not supported by this ROS2 bridge currently, please also see #73

[guru-florida]

Ok, I figured out that the ros2 bridge is trying to send the param get/set request to a rosapi node that is part of ros2-web-suite. I tried getting that working and got it running but doesnt work. However, in the process learned a thing or two about managing ROS2 parameters via the get/set_parameter service calls on each node. The ros2-web-bridge has no problem calling services so I would say this is the preferred way to manage parameters in ROS2 and no rosapi node needed!

I wrote some code. I could add to Ros class and do a PR if you like. I did parameter getter/setters but didnt do param enumeration yet.

export enum ParameterType {
    NOT_SET=0,
    BOOL=1,
    INTEGER=2,
    DOUBLE=3,
    STRING=4,
    BYTE_ARRAY=5,
    BOOL_ARRAY=6,
    INTEGER_ARRAY=7,
    DOUBLE_ARRAY=8,
    STRING_ARRAY=9,
}

export interface Parameter {
    node: string;
    name: string;
    typeid: ParameterType;
    value: any;
}

interface ServiceParameterValue {
    type: number;

    //  "Variant" style storage of the parameter value.
    bool_value?: boolean;
    integer_value?: number;
    double_value?: number;
    string_value?: string;
    byte_array_value?: number[];
    bool_array_value?: boolean[];
    iinteger_array_value?: number[];
    double_array_value?: number[];
    string_array_value?: string[];
}

interface ServiceParameter {
    name: string;
    value: ServiceParameterValue;
}

interface ServiceParameterResult {
    successful: boolean;
    reason: string;
}

export class GetParameterRequest {
    ros: ROS.Ros;
    node: string;
    name: string | string[];
}

export class SetParameterRequest {
    ros: ROS.Ros;
    node: string;
    params: ServiceParameter | [ServiceParameter];
}


function pull_parameter(p: ServiceParameterValue) {
    switch(p.type) {
        case ParameterType.NOT_SET: return null;
        case ParameterType.BOOL: return p.bool_value;
        case ParameterType.INTEGER: return p.integer_value;
        case ParameterType.DOUBLE: return p.double_value;
        case ParameterType.STRING: return p.string_value;
        case ParameterType.BYTE_ARRAY: return p.byte_array_value;
        case ParameterType.BOOL_ARRAY: return p.bool_array_value;
        case ParameterType.INTEGER_ARRAY: return p.iinteger_array_value;
        case ParameterType.DOUBLE_ARRAY: return p.double_array_value;
        case ParameterType.STRING_ARRAY: return p.string_array_value;
        default:
            console.warn("no way to determine value from Parameter ", p);
            break;
    }
}

/* Get/Set METHODS
 * I had these as part of a class, they could be added to the ROSLIB.Ros class.
 */
    public getParameters(request: GetParameterRequest) {
        let svc = new ROS.Service({
            ros: request.ros,
            name: request.node+'/get_parameters',
            serviceType: 'rcl_interfaces/srv/GetParameters'
        });

        const param_names = Array.isArray(request.name)
            ? request.name
            : [ request.name ];
        let svc_request = new ROS.ServiceRequest({
            names: param_names
        });

        return new Promise<Parameter[]>( (resolve,  reject) => {
            svc.callService(svc_request, response => {
                if(Array.isArray(response.values)) {
                    // convert parameters to javascript friendly
                    resolve( response.values.map( (v: ServiceParameterValue, idx: number) => ({
                        node: request.node,
                        name: param_names[idx],
                        typeid: v.type,
                        value: pull_parameter(v)
                    } as Parameter)));
                }
            }, reject);
        });
    }

    public setParameters(request: SetParameterRequest) {
        let svc = new ROS.Service({
            ros: request.ros,
            name: request.node+'/set_parameters',
            serviceType: 'rcl_interfaces/srv/SetParameters'
        });

        const params = Array.isArray(request.params)
            ? request.params
            : [ request.params ];
        let svc_request = new ROS.ServiceRequest({
            parameters: params
        });

        return new Promise<ServiceParameterResult[]>( (resolve,  reject) => {
            svc.callService(svc_request, response => {
                if(Array.isArray(response.results)) {
                    // convert parameters to javascript friendly
                    resolve( response.results as ServiceParameterResult[] );
                }
            }, reject);
        });
    }

`

[minggangw]

Absolutely, please submit your PR, thanks!

[guru-florida]

Sounds good. I got param enumeration too. I will fork and integrate changes and take a week to test in my own system before submitting the PR. So give me a week's time. Thanks!

I will also be doing service calls for Node Lifecycle management so I may follow up with a second PR on that one as well.