ros2_service_load_balancing

This package helps ROS2 services implement load balancing functionality.

see overview slide deck for more information.

How to build load balancing service application

In ROS2 environment (such as Jazzy, rolling)

Use rolling as example

$ source /opt/ros/rolling/setup.bash
$ mkdir -p ros2_ws/src && cd ros2_ws/src
$ git clone https://github.com/Barry-Xu-2018/ros2_service_load_balancing.git
$ cd ..
$ colcon build

How to run

Use add_two_ints_server (service server) and add_two_ints_client_async (service client) as an example to introduce how to use load balancing service application

launch service load balancing application

Service load balancing application needs to run first.

$ source /PATH/TO/ros2_ws/install/setup.bash
$ ros2 run service_load_balancing service_load_balancing -s add_two_ints -t example_interfaces/srv/AddTwoInts --strategy less_requests -i 1

The application parameters are introduced as follows

Usage:
    /root/ros2_ws/install/service_load_balancing/lib/service_load_balancing/service_load_balancing [-h|--help] [-s|--service-name SERVICE_NAME] [-t|--service-type SERVICE_TYPE] [--strategy XXX] [-i|--interval TIME]
       --strategy choose one of "round_robin", "less_requests" and "less_response_time"
                  If not set, "round_robin" is used as default.
                  "round_robin": select the service server in order.
                  "less_requests": select the service server with the fewest requests.
                  "less_response_time": select the service server with the shortest average response time.
       --interval Interval to discovery service servers. Unit is second.
                  If not set, default is 1s.

After run, you will get the below output

   Load balancing service name: /load_balancing/add_two_ints
                  Service type: example_interfaces/srv/AddTwoInts
       Load balancing strategy: less_requests
  Interval of server discovery: 1s
------------------------------
Service client remap service name to /load_balancing/add_two_ints
Service server remap service name to /load_balancing/add_two_ints/XXX
------------------------------

launch service server

The service server can refer to the above hint in log output to remap the service name for using the load balancing service.
Assume we start with 2 service servers. Of course, you can add service servers at any time.
In a new terminal,

$ source /opt/ros/rolling/setup.bash
$ ros2 run demo_nodes_cpp add_two_ints_server --ros-args -r add_two_ints:=load_balancing/add_two_ints/s1

In another new terminal,

$ source /opt/ros/rolling/setup.bash
$ ros2 run demo_nodes_cpp add_two_ints_server --ros-args -r add_two_ints:=load_balancing/add_two_ints/s2

Note that you must use different name under load_balancing/add_two_ints/.

launch service client

We can run any number of service clients to connect to the service.

$ source /opt/ros/rolling/setup.bash
$ ros2 run demo_nodes_cpp add_two_ints_client_async --ros-args -r add_two_ints:=load_balancing/add_two_ints