Errors in calling rosapi (ros2)

[justinscorringe]

Expected Behavior

Trying a call_service with rosapi/topics on the ros2 distro, returns this error. The caller works with ros1 installations fine. Is the protocol changed for ros2?

Actual Behavior

[ERROR] [rosbridge_websocket]: [Client 2] [id: rosbridge-control] call_service NonexistentFieldException: Message type rosapi/Topics_Request does not have a field _structure_needs_at_least_one_member

Steps to Reproduce the Problem

1. Launch rosbridge_server websocket and rosapi
2. {"op":"call_service","service":"/rosapi/topics","id":"rosbridge-control","args":["rosapi/Topics"]}

When doing ros2 service call;

rocos@rocosnuc:~/ros2_ws$ ros2 service call /rosapi/topics rosapi/Topics
waiting for service to become available...
requester: making request: rosapi.srv.Topics_Request(structure_needs_at_least_one_member=0)

response:
rosapi.srv.Topics_Response(topics=['/client_count', '/connected_clients', '/parameter_events', '/rosout'], types=['std_msgs/msg/Int32', 'rosbridge_msgs/msg/ConnectedClients', 'rcl_interfaces/msg/ParameterEvent', 'rcl_interfaces/msg/Log'])

So the ros2 service is working. But doesn't send json response.

Specifications

• ROS Version (echo $ROS_DISTRO): Dashing
• OS Version (grep DISTRIB_CODENAME /etc/lsb-release): ubuntu 18.04
• Rosbridge Version (roscat rosbridge_server package.xml | grep '<version>'): ros2 1.0.2
• Tornado Version (python -c 'import tornado; print tornado.version'): 4.5.3

[justinscorringe]

ros2/ros2cli#297

Could be related to this, have merged the fixes into my build but am getting the same error

[justinscorringe]

Same error persists across crystal/dashing/eloquent. Rosapi service call no longer works on its own in eloquent, 'type' error.

[dirk-thomas]

The fact that you are seeing a field _structure_needs_at_least_one_member indicates that you are not using the latest code on either of the distributions. Are you using the Debian packages or a from-source build? For the former please include the version number of all the involved packages (e.g. rosapi, rosidl_generator_py, etc.). For the later please make sure that you are having the latest state of the sources (share the exact hashed shown by vcs export --exact) and have fully rebuild them.

[dirk-thomas]

Same error persists across crystal/dashing/eloquent.

I tried this on Eloquent. Can you please double check that this is still a problem on Eloquent?

[dirk-thomas]

Dashing doesn't have a patch which has been for Eloquent atm. I proposed a backport in ros2/rosidl_python#93.

[justinscorringe]

Purged everything and now that error is gone: however in rosapi/proxy.py;
get_service_info needs to beupdated to get_service_server_info, and all is good :)

[dirk-thomas]

get_service_info needs to beupdated to get_service_server_info

@justinscorringe Can you please create a pull request for the described change.

ros2/ros2cli#408 makes sure the same API works for Dashing too.

[justinscorringe]

Made PR #447

[justinscorringe]

I'm still having an erronous time exercising all of the rosapi calls, providing commands functional on past examples of rosbridge protocol;

[ERROR] [rosbridge_websocket]: Exception calling subscribe callback: 'Time' object has no attribute 'secs'

[ERROR] [rosbridge_websocket]: [Client 3] [id: rosbridge-f245961f3674f9c1] call_service NonexistentFieldException: Message type rosapi/MessageDetails_Request does not have a field _type

[ERROR] [rosbridge_websocket]: Exception calling subscribe callback: 'dict_values' object is not callable

I may have to sift through these one at a time to update on either my end or rosbridge

[justinscorringe]

Could you please advise correct format of calling rosapi services in terminal, I am having type errors with eloquent change

[dirk-thomas]

If you could provide exact ready-to-run steps to reproduce the problem I am happy to try them and provide feedback what needs change.

[justinscorringe]

Fresh eloquent install, fresh ros2 branch clone of rosbridge and PR #447 applied before colcon build, environments sourced, ros2 run rosapi.py and rosbridge_websocket (launch xml seems to throw error)

rosapi/Topics and subscriptions work correctly and send response i want.

Websocket call (taken from wireshark to be sure)

{"op":"call_service","service":"/rosapi/message_details","id":"rosbridge-926d1d182dba4969","args":["rosbridge_msgs/msg/ConnectedClients"]}

Return

{"op": "service_response", "service": "/rosapi/message_details", "values": "Message type rosapi/MessageDetails_Request does not have a field _type", "result": false, "id": "rosbridge-926d1d182dba4969"}

[github-actions]

This issue has been marked as stale because it has been open for 180 days with no activity. Please remove the stale label or add a comment to keep it open.

[ussefdesouky]

Hello, I'm trying to build a 2d map on a web page using rosbridge, but this is my error when trying to subscribe on the /map topic.

[rosbridge_websocket-1] [ERROR] [1646804810.213169857] [rosbridge_websocket]: Exception calling subscribe callback: a bytes-like object is required, not 'str'