customresources/

README

CustomResources

This example demonstrates several ways RDK can be extended with custom resources. It contains several sections. Note that make is used throughout to help script commands. The actual commands being run should be printed as they are used. You can also look in the various "Makefile" named files throughout, to see the exact targets and what they do.

APIs

APIs represent new types of components or services, with a new interface definition. They consist of protobuf descriptions for the wire level protocol, matching Go interfaces, and concrete Go implementations of a gRPC client and server.

gizmoapi

Custom (component) api called "Gizmo" (acme:component:gizmo). Note that this is split into two files. The content of wrapper.go is only needed to support reconfiguration during standalone (non-modular) use.

summationapi

Custom (service) api called "Summation" (acme:service:summation).

protos

This folder contains the protobuf for the above two APIs. Only the .proto files are human modified. The rest is generated automatically by running "make" from within this directory. Note that the generation is performed using the "buf" command line tool, which itself is installed automatically as part of the make scripting. To generate protocols for other languages, other tooling or commands may be used. The key takeaway is that just the files with the .proto suffix are needed to generate the basic protobuf libraries for any given language.

Models

Models are concrete implementations of a specific type (API) of component or service.

mygizmo

A specific model (acme:demo:mygizmo) that implements the custom Gizmo API.

mysum

A specific model (acme:demo:mysum) that implements the custom Summation API. Simply adds or subtracts numbers.

mybase

Custom component (acme:demo:mybase) that implements Viam's built-in Base API (rdk:service:base) and in turn depends on two secondary "real" motors from the parent robot (such parental dependencies only work in modules, not as remote servers.)

mynavigation

Custom service (acme:demo:mynavigation) that implements Viam's built-in Nativation API (rdk:service:navigation) and only reports a static location from its config, and allows waypoints to be added/removed. Defaults to Point Nemo.

Demos

Each demo showcases an implementation of custom resources. They fall into two categories.

• One is a module, which is the newer, preferred method of implementing a custom resource. It involves building a small binary that will (after configuration) be automatically started by a parent-viam server process, and communicate with it via gRPC over a Unix (file-like) socket on the local system. All configuration is done via the single parent robot, with relevant bits being passed to the module as necessary.

• The other demo is the older, deprecated method, which is creating a standalone robot server (very similar to viam-server itself) with the new/custom component, and other non-needed parts stripped out, and then using that as a "remote" from a parent viam-server (even though it would technically run on the same local machine.) This requires two separate configs, one for the parent, and one for the custom server.

complexmodule

This demo is centered around a custom module that supports all four of the custom models above, including both custom APIs. A client demo is also included in a sub folder.

Running

• Start the server make run-module
  • This uses module.json
  • This automatically compiles the module itself first, which can be done manually with make module.
• In a separate terminal, run the client with make run-client (or move into the client directory and simply run make.)

Notes

In the module.json config, the module is defined near the top of the file. The executable_path there is the filesystem path to the executable module file. This path can be either relative (to the working directory where the server is started) or absolute. The provided example is relative to the demo itself, and on real installations, absolute paths may be more reliable. Ex: "/usr/local/bin/custommodule"

Reconfiguration should work live. Simply edit the module.json file while the server is running and save. The server should detect the changes and update accordingly. You can try adjusting the coordinates for the mynavigation service, flip the "subtract" value of the mysum service, or change the name of "arg1" in mygizmo, then re-run the client to see that it's changed things.

Additionally, you can comment out the "Reconfigure()" method in either mygizmo, mynavigation, or mysum to see how reconfiguration becomes replacement. If a resource doesn't support direct reconfiguration, it will automatically be recreated with the new config and replaced instead.

simplemodule

This is a minimal version of a custom resource module, using the built-in Generic API, and where everything for the module is in one file. It has a simple "counter" component model included, which uses the rdk:component:generic interface. This component simply takes numbers and adds them to a running total, which can also be fetched. This also contains a client demo similar to the complex example.

Running

• Same steps as the complex demo above.
• Start the server make run-module
  • This uses module.json
  • This automatically compiles the module itself first, which can be done manually with make module.
• In a separate terminal, run the client with make run-client (or move into the client directory and simply run make.)

remoteserver

This demo provides a standalone server that supports the "mygizmo" component only, intended for use as a "remote" from a parent. The custom server is started and then a parent process can be run which will use the custom server as a "remote" and its custom resource(s) will be mapped through the parent as part of the larger robot. There is also a client demo.

Running

• From within the demo's directory
• Run the server implementing custom resources make run-remote.
  • This uses remote.json
• From a second terminal, run a standard server connecting to the custom resource server as a remote make run-parent.
  • This uses parent.json
• From a third terminal, run the client that has loaded the custom gizmo api, and talks to it via the parent make run-client.

Notes

The remote server method of implementing custom resources is deprecated, and the modular methods should be used instead. This demo is maintained for testing purposes. Remotes themselves are still used for connecting to viam-server instances on other physical systems however, which was their original intent.